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POINT TO POINT WIRELESS INFRARED LIGHT COMMUNICATION
GOB YIAW BOONG
Tesis Dikemukakan Kepada Fakulti Kejuruteraan Universiti Malaysia Sarawak
Sebagai Memenuhi Sebabagian daripada Syarat Penganugerahan Sarjana Muda Kejuruteraan
Dengan Kepujian (Kejuruteraan Electronik dan Telekomunikasi) 2000
DEDICATION
For God so loved the world that he gave his only Son so that everyone who believes in him will not perish but have eternallwe
[John 316]
II
au
PENGBARGAAN
Penulis ingin merakam penghargaan ikhlas kepada penyelia tesis EnNg Liang Yew dan
En Hushari Hj Zen di alas keperihatinan dan sokongan yang diberi sepanjang tempoh
penyelidikan tesis ini
Penghargaan kepada Pembantu Makmal En Zakaria atas sokongan beliau dalam
menjayakan projek tesis ini
Penghargaan juga diberi kepada sesiapa yang samada secara langsung atau tidak
langsung membantu dalam projek ini
III
i
ABSTRAK
Adalah menjadi satu masalah untuk mencapai maklumat di kawasan yang terpencil
Pembangunan rangkaian untuk kawasan tersebut biasanya bennasalah disebabkan beberapa
faktor Pertama kawasan tersebut adalah jauh dari rangkaian yang sediaada Kedua faktor
geographi kos pelaburan kos operasi serta pulangan yang rendah tidak menggalakan
syarikat telekomunikasi melabur di kawasan tersebut Ketiga tenaga mahir diperlukan kos
buruh mungkin tinggi Keempat lesen dari pihak berkuasa tempatan mungkin diperlukan
Kertas ini akan membincangkan satu pendekatan yang membolehkan individu berkomunikasi
secara tanpa wayar dengan menggunakan standard RS232 dan cabaya Laser sebagai
pembawa maklumat Perbincangan kertas ini merangkumi asas-asas rangkaian
telekommunikasi piawaian RS232 kaedah pemodulatan tanpa wayar analisa perisian dan
litar sistem tersebut Cadangan kertas ini ialah menggunakan RS232 Tranceiver yang
kedapatan dari Electronics Australia bertarikh October 1999 muka surat 56-61
IV
ABSTRACT
Is always a problem to access the data at a remote area The implementation on wireless
network for remote area is difficult due to certain reason First The places was isolated and
far from existing telecommunication access point Second the geographical factor high
investment cost of operation and maintenance low return will made a telecommunication
firm reluctant to put their investment in such area Third a highly skill personnel is need and
labour cost could be higher Forth the license from the authority concern might be required
Therefore this paper was to discuss a solution that allowed individual to communicate via
RS232 port using Laser light as communication medium This topics will cover the
fundamental of telecommunication network standard RS232 interface standard wireless
modulation technique Laser fundamental hardware and software analysis This paper is
designing to use RS232 Laser transceiver adapted from Electronics Australia dated Oct 1997
pg56-61
v
TABLE OF CONTENTS
Contents Pages
iiDEDICATION
ACKNOWLEDGEMENT iii
ABSTRAK iv
ABSTRACT v
TABLE OF CONTENTS vi
LIST OF ILLUSTRATION ix
Chapter 1 Wireless Communication An Overview
10 An Introduction 1 11 Wireless Network 1 12 Fundamental ofa Wireless Internet System 2 13 The Purpose of This Paper 2
CbapterZ RSZ3Z Interface amp Serial Communication
20 Overview 5 21 RS232 Pin Abbreviation 6 22 DART 7 23 Serial Communication 8 24 Parallel Communication 8 25 Asynchronous amp Synchronous Data 9 26 The Start Data Parity and Stop bit 10
261 Start bit 11 262 Data bits 11 263 Parity bits 11 264 Stop bit 12
27 Data Transmit amp Receive Process 12 281 Transmit ofa character 12 282 Receive ofa character 13
28 COM Port Setting 14
VI
Chapter 3 Laser as a Communication Medium
30 Fundamental of light 15 31 What is Laser 17 32 Characteristic ofa Laser Beam 19 33 Type ofLaser 20
331 Semiconductor Laser 20 332 Gas Lasers 20 333 Solid State Laser Nd YAG Laser 21
34 Light Modulation Scheme 22 35 Several Optical Modulation Techniques 25
351 Analog modulation 25 352 Pulse Modulation Technique 27
Chapter 4 Modulation Technique for Wireless System
40 Why Need Modulation 29 41 Amplitude Modulation 29 42 Frequency Modulation-AMPS 30 43 Generation ofFrequency Modula 31 44 Digital Modulation Technique 32 45 Frequency Shift Keying 32 46 Phase Shift Keying 35 47 Quadrature Phase Shift Keying 36 48 Offset Quadrature Phase Shift Keying 37 49 Minimum Shift Keying 39
Chapter 5 Laser Safety
50 Laser Beam Hazard 41 51 Safety Precaution amp Control Procedure 41 52 Class ofLaser 42
Chapter 6 System Design
60 Basic Overview 43 61 System Design 44 62 The Block Diagram 44 63 Function For Each Block 45 64 The Construction 45 65 Construction PCB 47 66 Observation 47 67 Testing
VII
p
Chapter 7 Software Analysis
70 Software Overview 50 71 Include Header File 53 72 Define The Setting 54 73 The Other Function 54 74 The Other Testing Program 55
ChapterS Conclusion
80 The Conclusion 58 81 The Future Work 58
APPENDIX A 60
REFERENCE 61
vm
LIST OF ILLUSTRATION
Figure Page
18 THE BLOCK DIAGRAM OF TYPICAL NETWORK 2
Ib CELCOMtrade DATA2GONETWORK
Ie SIMPLEST POINT-TO-POINT DATA COMMUNICATION VIA
2
RS232 LASER TRANSCEIVER 4
28 THE RS232 PIN CONFIGURATION 6
2b A NULL MODEM CONFIGURATION 6
2e DETAIL EXPLANATION OF RS232 PIN ABBREVIATION 7
2d THE SERIAL PORT BASE REGISTER 8
2e A PARALLEL PRINTER TO COMPUTER CONFIGURATION 9
2f SYNCHRONOUS DATA FORMAT 10
2g ASYNCBRONOUS DATA FORMAT 10
2h THE DATA BIT FORMAT 11
2i USART BLOCK DIAGRAM 13
3a ELECTRIC AND MAGNETIC FIELD IN PLANE ELECTROMAGNETIC WAVE 16
3b ILLUSTRATION OF ENERGY DIAGRAM FOR TWO LEVEL ENERGY SYSTEM ABSORPTION STIMULATED EMISSION 19 SPONTANEOUS EMISSION
3e SPATIAL COHERENT AT FOCUSING POINT 20
IX
po
3d EXCITATION OF GASEOUS LASER MEDIUM REFLECTION 21 OF PHOTON DURING STIMULATED EMISSION EXITING PHOTON IN LASER BEAM
SIGNAL (C) INTENSITY OF LIGHT
3e SCHEMATIC DIAGRAM FOR AN END PUMPED ND YAGLASER 22
3f THE ELECTROMAGNETIC SPECTRUM 23
3g AMPLITUDE MODULATION OF OPTICAL LIGHT BEAM 24
3h NON RETURN ZERO FORMAT 24
3i RETURN TO ZERO FORMAT 24
3j USING FM MODULATION TO MODULATED INTENSITY OF tiGHT (A) MASSAGE AMPUTUDE (B) FM MODULATION 25
4a AM SIGNAL MODULATION 30
4b FM SIGNAL MODULATION 31
4c FREQUENCY MODULATION 32
4d FSKFORMAT 33
4e FORMATION OF FSK SIGNAL 34
4f NON COHERENT DEMODULATION 35
4g COHERENT DEMODULATION 35
4h PSK WAVEFORM 36
4i THE GENERATION OF QPSK SIGNAL 37
4j OQPSK WAVEFORM (HALF SYMBOL OFFSET) 38
4k GENERATION ON OQPSK SIGNAL 39
41 GENERATION OF MSK WAVEFORM 40
4m OUTPUT WAVEFORM OF MSK SIGNAL 41
x
5a LASER WARNING LABEL 42
6a SIMPLE BLOCK DIAGRAM RS131 LASER COMMUNICATION SYSTEM 43
6b BLOCK DIAGRAM OF RS131 LASER TRANSCEIVER 44
6c SCHEMATIC OF TRANSCEIVER 45
6d PCB LAYOUT 46
6e DB9JUMPERING 48
7a THE HEADER FILE 54
7b THESETI1NG 55
7c BIOSCOM EXAMPLE 56
7d BIOS_SERIALCOM EXAMPLE 57
XI
CHAPTERt
WIRELESS COMMUNICATION AN OVERVIEW
to An Introduction
A communication occurs when there was an infonnation flow The word
telecommunication is derive from the Greek tele far of and communicare to share
[1] The communication is the process of transferring interpreting and processing
infonnation (data) among the people machines and place This process implies that we
need a sender a medium and a receiver to perform infonnation flow Therefore the
telecommunication is the process of exchanging the data of information in any useable
fonn in any natural delivery among two or more user by using radio wire and light and
other mechanical means
1t Wireless Network
Consider a cellular telephone system that provided coverage in a geographical
area as figure ta shown
To provide wireless communication within a region a Radio Base Station (RBS) must be
set up The Radio Base Station will perfonn the function as access point to the mobile
user and a connection with Mobile Switching Center A mobile user connected to base
station through Common Air Interface which can also called Handshaking ProtocoL [2]
The Radio Base Station will connect to mobile Switching Center through landline The
mobile switching center will provide connectivity to Public Switch Telephone Network
The PSTN Switching Center will provide connectivity to global network
The basic concept of a wireless network was to establishing the mobile user to a base
station followed by connection with mobile switch center and from mobile center
connected to global network
1
Mobile SWltchlna Center(MSC) or
Mobile Telephone SWItohlna omce Voice and Data link
(Landline or ~microwave)
Q ~ ~P-
PSTN
regRadio Link air interface
Figure la The Block Diagram of a Typical Wireless Network [ 2 ]
PSTN network and mobile network will connect by either fix-line or radio wave For the
fixmiddotline It will be twisted copper cable coaxial cable fiber optics cable For the radio
wave it either use microwave and satellite link The characteristic of a PSTN network is
the user was fix at one location while the mobile network allowed the user to move
within the coverage area The process of moving within the coverage area called
Roaming
12 Fundamental of a Wireless Intemet System
To accessing the internet a cellular user need to use a PCMCIA card with the adapter to
connected to laptop in the area where PSTN line was not accessible For example the
product of Celcom Data2Go for wireless data communication can have the following
function shy
e Electronic mail system
e Sending and receiving fax
2
bull Accessing Company database
bull Submit customer order
bull On-line information service
bull accessing Internet-surfing into Netscape
bull terminal mode- billinwregistration
The network ofData2Go by Celcomtradeas shown shy
Figure Ib Celcomtrade Data2Go Network 14 I
Software uses for this type ofnetwork are
bull Delrina WinFaxPro
bull Microsoft Mail
bull Netscape
bull Lotus Notes
13 The purpose of this paper
The main purpose of this project is to develop a useable technique that suitable for
sending data wireless via RS232 communication port The system component will consist
of a desktop computer that act as input device a standard RS232 interface a transceiver
for transmit and receive signal and a modify laser poniter The suggested system will be
3
set and tested in a point-to-point configuration As the figure show below the network
diagram stated shy
J -~HJj----tcooo ~ IEco~codl---=RS=232=--_~ Personal computer Signal RS232 Laser Transceiver RS2321aser Transceiver Personal computer
Figure lc The Simples point to point data communication via RS131laser transceiver
4
Cbapter2
RS-232 INTERFACE AND SERIAL COMMUNICATION
20 Overview
RS 232 Interface in a simple universal well knows data interface RS means
Recommended Standard1 The female connector attaches to Data Communication
Equipment and male connector attaches to Data Terminal Equipment Mostly today PCs
are equipped with two RS232 ports via COMI or COM2 The additional COM port
COM3 and COM4 required additional card
RS-232 defines 25-pin communication line Every line has their own function to
accessing data The configurations ofevery pin layout are show in figure 2a
Normally The ground signal refers to pin 7 Two computers can communicate by using a
null modem A null modem is a special made direct cable and connector It is functioning
like a modem but has limited transmission range Figure 2b illustrated the common
method to wiring a null modem Pin2 and pin3 are wire together and all the cables are
connect in such a way a modem simulated between two computers
The electrical characteristic define by RS232 as
(a) Total capacitance not less than 2500 pF
(b) (b) A binary high logic output lines is + 5to + 15 volts input lines is from +3
to + 15 volts
(c) A binary low logic output lines is from -5 to -15 volts input lines is from -3
to -15 volts
(d) output lines voltages -5 and +5 -3 and +3 volts for input lines are undefined
5
Shelld~ Secondary
tntnsmltted data Transmlttins
Signal element timlne (DCEoTE)
Secondary
Relcetver received data
Signal tlmlne(DCEoTE) Looak
Loopok Secondary
Request To8end
DTERudy
Rem_ Loopb8ok amp Signal Qua
Decmlctor RinS indicator
l reg
Transmitted Data
Request to Send
DCEReady
Rivedline 818nal Detector
Reserved (Testing)
Secondary Received Lne Signel Detector
Recetve Data
reg
Crto8ent
Signal Ground Comman RetUrn
reg Rrved (Testing)
Datas18nal
I 10
rate ct UnusedTnulSmitter signal Signed
element -f
timing (DTE-DCE) bull Tnt Mode 8eooundary~ 13 c
To8ent~
Figure 2a The RS232 pin configuration [81
Pin Number Line Line Pin Number
2 m m 2
3 RD RD 3
4 RTS RTS 4
5 CTS CTS 5
6 DSR---- DSR 6
7 Common 7
8 DCD DCD 8
20 DTR DTR 20
22 R1 R1 22
Figure 2b A Null Modem Configuration [8]
6
21 The Explanation For RS1Jl Pin Abbreviation
Hence is the detail ofeach line in DB9 and DB25 function
Clear to Send (CTS)
Data Carrier Detect (OCR)
Data Set Ready (DSR)
Data Terminal Ready (DTR)
Receive Data (RO)
Ring Indicator (RI)
Requested to Send (RTS)
Transmit Data (TD)
asserted (logic state 1) by DCE it is ready to receive data
logic state 1 whenever there is data link in progress
logic state 1 when DCE is ready to communicated withDTE
logic state 1 when DTE is ready to communicated withDCE
use by DCE to send data to DTE
logic 1 by DCE when a ring is detect
logic state 1 by DTE when it want to transmit data toDCE
Use by DTE to send data to DCE
Figure lc The Detail Explanation of Abbreviation [ 8]
22 UART
UART Universal Asynchronous Receiver Transmitter is a special hardware in RS232
serial interface It sometime called as Asynchronous Communication Element
Most of the new personal computer today is equip with 16450 and 16550 UART The
function ofUART chip is to convert the parallel data to a serial data format that enable a
serial communication between two computers The UART chip also uses to convert back
7
the serial bits to parallel bits format The operation of UART mostly control by one or
more register The process of read writes data to register are through input and output
ports Figure ld showing the address of a UART for COMI and COM4
The UART have FIFO or First in First out buffer FIFO bring the meaning as the first
data to enter the buffer are first to leave The function of buffer is to hold data temporary
before it was feed to the transmission medium The modem 16550A UART have16 bytes
FIFO This means 16 bytes can be writes to UART before anything was overwrite The
16550 UART was necessary for a high-speed communication under windows or
application running under window environment
Serial port Base Register Port Address
COM 1 3F8H COM2 2F8H COM3 3E8H COM3 2E8H
Figure ld The Serial Port Base Register Port [7 ]
23 Serial Communication
Serial communication is transmission of data over a serial interface one data bit at a time
In other word data are transfer through and forth over a single wire Therefore serial
communication is more cost effective than parallel communication RS232 is an example
for serial communication interface
24 Parallel Interface
Parallel communication is a way to sending more than one data at a time (normally eight
data bits) over to a parallel device or a Com Port For an example a computer will send
eight data bits of information to a parallel printer A very simple diagram of parallel
communication was present as Figure 2e The parallel interfaces require separated wire
8
------_------------__shyp
for sending separated data and therefor allowed faster and efficient data transmission On
the other hand to setting up a parallel communication network will be more costly than
serial communication network
1 Printer Interface
1 3 4 5 6 7 8
1 Computer Interface
2 3 4 5 6 7 8
Figure 2e A parallel Printer to Computer Interface [7 ]
25 Asynchronous and synchronous data
For two devices to communicate a way of synchronizing data must be set There are two
way ofdata formatting by using either asynchronous or synchronous
The synchronous operation is such a way that for each line data transmit it has a
separated clock to synchronous that data on a time of period For example data are
transfer once in each direction to and from the computer The synchronous data format
was show in figure 2f
While the asynchronous data is such a way that data are synchronous without clock
Each time the data are transmitting the receiver need to figure out how fast the data is
running The frame of asynchronous data has start and stops bit In another world the
frame always added with additional start and stop bit The asynchronous data format was
show in figure 2g
9
01100011100 o 1 1 1 11 0 0 0 0 001 0110 1 1 0
Unique Code
Continuous Block
Direction offlow
Figure 2f Synchronous data format I 8 ]
Start Stop d7 d6 d5 d4 d3 d2 dl dO Start
1 0 1 0 1 1 0 0I 1 I IMSB LSB
Start bit Stop bit1 Data-bits 1 I
r space mark mark space mark space mark mark space space
Serial Communication
Figure 2g Asynchronous Data Format Adopted form [8]
26 The Start Parity and Stop bits
For two machines to communicate to each other first thing both machines must agree on
the rate of speed for data transfer Second thing is the data must fonnatted for
synchronous or asynchronous operation Therefor for asynchronous operation the data
fonnatted in such a way that contains start and stop bit
271 Start bit
10
The TD line at interface device (Pin3) will go high when no data been transmit To start
transmit a data Transmit serial device will set TD line to low by means ofa start bit The
synchronous operation of DCE is waiting the TD line sign change from high bit to low
bit than DCE pauses half of a bit time and start sampling the incoming data until all the
character has been completely transmit To maintain synchronimtion DCE always
sampling the incoming data string at middle ofeach bit
272 Data bits
The data bits are the bits that contain character Nonnallyone character contains eight
bits Hence is the data bits showing character Amiddot 4tH
l start bit 41----shy Data bits j
shy
I t I Io 0 0 0 0 0
1 1deg1 1
Figure 2h The Data bits Format ( 7 ]
273 Parity bits
Four basic fonns ofparity bits are NONE EVEN ODD MARK and SPACE NONE use
for transmits a character without parity bit EVEN parity use to indicate by send logic 1
after a character if there is an odd number of logic 1 bit after a character data bit
Otherwise logic for EVEN parity goes to zero Odd parity will indicate by sending logic
1 after a data of a character bits if there is an even number of logic 1 after a characters
data bits Otherwise logic for ODD parity goes to zero Mark is logic 1 parity bit after a
data character and SPACE is logic zero after the data character
11
274 Stop bits
The stop bit indicated the end of a character The serial device was always send logic 1
for stop bit
28 Data Transmit and Receive Process
281 Transmit of a character
Several steps take before characters are transmitting from processor to modem
For an example communication between processor and 8251A USART
First the processor configures UART according to the communication protocol
Second an instruction was send to UART and set the flag TxEN Next The processor
was send the character to the data buffer ofUART Then this data buffer transfer the
character to transmit buffer for preparation for transmission Once data buffer was
complete transfer the character and ready to receive a new character the TXRDY flag
will set When processor automatically write in data buffer TXRDY flag automatically
reset
Next RTS (Ready to Send)pin output pin ofUART will alerted by modem that the bits
are about to transmit RTS pin for UART is tie together with modem RTS pin while the
modem realizes about to receive character from UART CTS pin will activated Then the
character was automatically transfer to modem The internal flag TxEMPTY will set
once the character was completely transmit from UART to modem
282 Receive of a character
The process of data receiving was also take several sequence First processor configures
UART according to standard protocol Then to receive a character the processor sends a
12
p
instruction to activated the RxE flag Next DART need to be alerted about the data going
to be transmitted DSR (Data Set Ready) will activated DSR pin of DART and modem
are tied together therefore when processor read this flags and realizes that the modem
has characters to be transmitted to DART Once DSR signal been set processor set DTR
(data terminal ready) to high And once DTR pin is asserted characters was
automatically transfer out from modem Once the characters is receive by DART it
formatted the data according to their start stop parity bits The RxRDY activated when a
character was completely receive
The bock diagram ofDART was show in ftgUre 2i
transmittedT~_B_r ~Mode Register
Transmit Register-~ I I data
I [_~~~J lt-~--r I
Receiver Register L~~~l-~~mmg =71 -_Rece~~I_v-e_r-B_-un_e=r=_-_ ~_romL--_
Devices and bullControl LogiC
l Internal Transmitter I Bus c-- ~ Clocking
--_______________rece_i_ve_r__lt=__-T Circuitary
Figure 2i USART Bloek Diagram [8 ]
28 COM Port setting
COM Port is the port that allowed computer to communicated with other device
such as modem or printer The standard personal computer normally has four
communications port COM 1 and COM 2 are assign for external port All the
13
DEDICATION
For God so loved the world that he gave his only Son so that everyone who believes in him will not perish but have eternallwe
[John 316]
II
au
PENGBARGAAN
Penulis ingin merakam penghargaan ikhlas kepada penyelia tesis EnNg Liang Yew dan
En Hushari Hj Zen di alas keperihatinan dan sokongan yang diberi sepanjang tempoh
penyelidikan tesis ini
Penghargaan kepada Pembantu Makmal En Zakaria atas sokongan beliau dalam
menjayakan projek tesis ini
Penghargaan juga diberi kepada sesiapa yang samada secara langsung atau tidak
langsung membantu dalam projek ini
III
i
ABSTRAK
Adalah menjadi satu masalah untuk mencapai maklumat di kawasan yang terpencil
Pembangunan rangkaian untuk kawasan tersebut biasanya bennasalah disebabkan beberapa
faktor Pertama kawasan tersebut adalah jauh dari rangkaian yang sediaada Kedua faktor
geographi kos pelaburan kos operasi serta pulangan yang rendah tidak menggalakan
syarikat telekomunikasi melabur di kawasan tersebut Ketiga tenaga mahir diperlukan kos
buruh mungkin tinggi Keempat lesen dari pihak berkuasa tempatan mungkin diperlukan
Kertas ini akan membincangkan satu pendekatan yang membolehkan individu berkomunikasi
secara tanpa wayar dengan menggunakan standard RS232 dan cabaya Laser sebagai
pembawa maklumat Perbincangan kertas ini merangkumi asas-asas rangkaian
telekommunikasi piawaian RS232 kaedah pemodulatan tanpa wayar analisa perisian dan
litar sistem tersebut Cadangan kertas ini ialah menggunakan RS232 Tranceiver yang
kedapatan dari Electronics Australia bertarikh October 1999 muka surat 56-61
IV
ABSTRACT
Is always a problem to access the data at a remote area The implementation on wireless
network for remote area is difficult due to certain reason First The places was isolated and
far from existing telecommunication access point Second the geographical factor high
investment cost of operation and maintenance low return will made a telecommunication
firm reluctant to put their investment in such area Third a highly skill personnel is need and
labour cost could be higher Forth the license from the authority concern might be required
Therefore this paper was to discuss a solution that allowed individual to communicate via
RS232 port using Laser light as communication medium This topics will cover the
fundamental of telecommunication network standard RS232 interface standard wireless
modulation technique Laser fundamental hardware and software analysis This paper is
designing to use RS232 Laser transceiver adapted from Electronics Australia dated Oct 1997
pg56-61
v
TABLE OF CONTENTS
Contents Pages
iiDEDICATION
ACKNOWLEDGEMENT iii
ABSTRAK iv
ABSTRACT v
TABLE OF CONTENTS vi
LIST OF ILLUSTRATION ix
Chapter 1 Wireless Communication An Overview
10 An Introduction 1 11 Wireless Network 1 12 Fundamental ofa Wireless Internet System 2 13 The Purpose of This Paper 2
CbapterZ RSZ3Z Interface amp Serial Communication
20 Overview 5 21 RS232 Pin Abbreviation 6 22 DART 7 23 Serial Communication 8 24 Parallel Communication 8 25 Asynchronous amp Synchronous Data 9 26 The Start Data Parity and Stop bit 10
261 Start bit 11 262 Data bits 11 263 Parity bits 11 264 Stop bit 12
27 Data Transmit amp Receive Process 12 281 Transmit ofa character 12 282 Receive ofa character 13
28 COM Port Setting 14
VI
Chapter 3 Laser as a Communication Medium
30 Fundamental of light 15 31 What is Laser 17 32 Characteristic ofa Laser Beam 19 33 Type ofLaser 20
331 Semiconductor Laser 20 332 Gas Lasers 20 333 Solid State Laser Nd YAG Laser 21
34 Light Modulation Scheme 22 35 Several Optical Modulation Techniques 25
351 Analog modulation 25 352 Pulse Modulation Technique 27
Chapter 4 Modulation Technique for Wireless System
40 Why Need Modulation 29 41 Amplitude Modulation 29 42 Frequency Modulation-AMPS 30 43 Generation ofFrequency Modula 31 44 Digital Modulation Technique 32 45 Frequency Shift Keying 32 46 Phase Shift Keying 35 47 Quadrature Phase Shift Keying 36 48 Offset Quadrature Phase Shift Keying 37 49 Minimum Shift Keying 39
Chapter 5 Laser Safety
50 Laser Beam Hazard 41 51 Safety Precaution amp Control Procedure 41 52 Class ofLaser 42
Chapter 6 System Design
60 Basic Overview 43 61 System Design 44 62 The Block Diagram 44 63 Function For Each Block 45 64 The Construction 45 65 Construction PCB 47 66 Observation 47 67 Testing
VII
p
Chapter 7 Software Analysis
70 Software Overview 50 71 Include Header File 53 72 Define The Setting 54 73 The Other Function 54 74 The Other Testing Program 55
ChapterS Conclusion
80 The Conclusion 58 81 The Future Work 58
APPENDIX A 60
REFERENCE 61
vm
LIST OF ILLUSTRATION
Figure Page
18 THE BLOCK DIAGRAM OF TYPICAL NETWORK 2
Ib CELCOMtrade DATA2GONETWORK
Ie SIMPLEST POINT-TO-POINT DATA COMMUNICATION VIA
2
RS232 LASER TRANSCEIVER 4
28 THE RS232 PIN CONFIGURATION 6
2b A NULL MODEM CONFIGURATION 6
2e DETAIL EXPLANATION OF RS232 PIN ABBREVIATION 7
2d THE SERIAL PORT BASE REGISTER 8
2e A PARALLEL PRINTER TO COMPUTER CONFIGURATION 9
2f SYNCHRONOUS DATA FORMAT 10
2g ASYNCBRONOUS DATA FORMAT 10
2h THE DATA BIT FORMAT 11
2i USART BLOCK DIAGRAM 13
3a ELECTRIC AND MAGNETIC FIELD IN PLANE ELECTROMAGNETIC WAVE 16
3b ILLUSTRATION OF ENERGY DIAGRAM FOR TWO LEVEL ENERGY SYSTEM ABSORPTION STIMULATED EMISSION 19 SPONTANEOUS EMISSION
3e SPATIAL COHERENT AT FOCUSING POINT 20
IX
po
3d EXCITATION OF GASEOUS LASER MEDIUM REFLECTION 21 OF PHOTON DURING STIMULATED EMISSION EXITING PHOTON IN LASER BEAM
SIGNAL (C) INTENSITY OF LIGHT
3e SCHEMATIC DIAGRAM FOR AN END PUMPED ND YAGLASER 22
3f THE ELECTROMAGNETIC SPECTRUM 23
3g AMPLITUDE MODULATION OF OPTICAL LIGHT BEAM 24
3h NON RETURN ZERO FORMAT 24
3i RETURN TO ZERO FORMAT 24
3j USING FM MODULATION TO MODULATED INTENSITY OF tiGHT (A) MASSAGE AMPUTUDE (B) FM MODULATION 25
4a AM SIGNAL MODULATION 30
4b FM SIGNAL MODULATION 31
4c FREQUENCY MODULATION 32
4d FSKFORMAT 33
4e FORMATION OF FSK SIGNAL 34
4f NON COHERENT DEMODULATION 35
4g COHERENT DEMODULATION 35
4h PSK WAVEFORM 36
4i THE GENERATION OF QPSK SIGNAL 37
4j OQPSK WAVEFORM (HALF SYMBOL OFFSET) 38
4k GENERATION ON OQPSK SIGNAL 39
41 GENERATION OF MSK WAVEFORM 40
4m OUTPUT WAVEFORM OF MSK SIGNAL 41
x
5a LASER WARNING LABEL 42
6a SIMPLE BLOCK DIAGRAM RS131 LASER COMMUNICATION SYSTEM 43
6b BLOCK DIAGRAM OF RS131 LASER TRANSCEIVER 44
6c SCHEMATIC OF TRANSCEIVER 45
6d PCB LAYOUT 46
6e DB9JUMPERING 48
7a THE HEADER FILE 54
7b THESETI1NG 55
7c BIOSCOM EXAMPLE 56
7d BIOS_SERIALCOM EXAMPLE 57
XI
CHAPTERt
WIRELESS COMMUNICATION AN OVERVIEW
to An Introduction
A communication occurs when there was an infonnation flow The word
telecommunication is derive from the Greek tele far of and communicare to share
[1] The communication is the process of transferring interpreting and processing
infonnation (data) among the people machines and place This process implies that we
need a sender a medium and a receiver to perform infonnation flow Therefore the
telecommunication is the process of exchanging the data of information in any useable
fonn in any natural delivery among two or more user by using radio wire and light and
other mechanical means
1t Wireless Network
Consider a cellular telephone system that provided coverage in a geographical
area as figure ta shown
To provide wireless communication within a region a Radio Base Station (RBS) must be
set up The Radio Base Station will perfonn the function as access point to the mobile
user and a connection with Mobile Switching Center A mobile user connected to base
station through Common Air Interface which can also called Handshaking ProtocoL [2]
The Radio Base Station will connect to mobile Switching Center through landline The
mobile switching center will provide connectivity to Public Switch Telephone Network
The PSTN Switching Center will provide connectivity to global network
The basic concept of a wireless network was to establishing the mobile user to a base
station followed by connection with mobile switch center and from mobile center
connected to global network
1
Mobile SWltchlna Center(MSC) or
Mobile Telephone SWItohlna omce Voice and Data link
(Landline or ~microwave)
Q ~ ~P-
PSTN
regRadio Link air interface
Figure la The Block Diagram of a Typical Wireless Network [ 2 ]
PSTN network and mobile network will connect by either fix-line or radio wave For the
fixmiddotline It will be twisted copper cable coaxial cable fiber optics cable For the radio
wave it either use microwave and satellite link The characteristic of a PSTN network is
the user was fix at one location while the mobile network allowed the user to move
within the coverage area The process of moving within the coverage area called
Roaming
12 Fundamental of a Wireless Intemet System
To accessing the internet a cellular user need to use a PCMCIA card with the adapter to
connected to laptop in the area where PSTN line was not accessible For example the
product of Celcom Data2Go for wireless data communication can have the following
function shy
e Electronic mail system
e Sending and receiving fax
2
bull Accessing Company database
bull Submit customer order
bull On-line information service
bull accessing Internet-surfing into Netscape
bull terminal mode- billinwregistration
The network ofData2Go by Celcomtradeas shown shy
Figure Ib Celcomtrade Data2Go Network 14 I
Software uses for this type ofnetwork are
bull Delrina WinFaxPro
bull Microsoft Mail
bull Netscape
bull Lotus Notes
13 The purpose of this paper
The main purpose of this project is to develop a useable technique that suitable for
sending data wireless via RS232 communication port The system component will consist
of a desktop computer that act as input device a standard RS232 interface a transceiver
for transmit and receive signal and a modify laser poniter The suggested system will be
3
set and tested in a point-to-point configuration As the figure show below the network
diagram stated shy
J -~HJj----tcooo ~ IEco~codl---=RS=232=--_~ Personal computer Signal RS232 Laser Transceiver RS2321aser Transceiver Personal computer
Figure lc The Simples point to point data communication via RS131laser transceiver
4
Cbapter2
RS-232 INTERFACE AND SERIAL COMMUNICATION
20 Overview
RS 232 Interface in a simple universal well knows data interface RS means
Recommended Standard1 The female connector attaches to Data Communication
Equipment and male connector attaches to Data Terminal Equipment Mostly today PCs
are equipped with two RS232 ports via COMI or COM2 The additional COM port
COM3 and COM4 required additional card
RS-232 defines 25-pin communication line Every line has their own function to
accessing data The configurations ofevery pin layout are show in figure 2a
Normally The ground signal refers to pin 7 Two computers can communicate by using a
null modem A null modem is a special made direct cable and connector It is functioning
like a modem but has limited transmission range Figure 2b illustrated the common
method to wiring a null modem Pin2 and pin3 are wire together and all the cables are
connect in such a way a modem simulated between two computers
The electrical characteristic define by RS232 as
(a) Total capacitance not less than 2500 pF
(b) (b) A binary high logic output lines is + 5to + 15 volts input lines is from +3
to + 15 volts
(c) A binary low logic output lines is from -5 to -15 volts input lines is from -3
to -15 volts
(d) output lines voltages -5 and +5 -3 and +3 volts for input lines are undefined
5
Shelld~ Secondary
tntnsmltted data Transmlttins
Signal element timlne (DCEoTE)
Secondary
Relcetver received data
Signal tlmlne(DCEoTE) Looak
Loopok Secondary
Request To8end
DTERudy
Rem_ Loopb8ok amp Signal Qua
Decmlctor RinS indicator
l reg
Transmitted Data
Request to Send
DCEReady
Rivedline 818nal Detector
Reserved (Testing)
Secondary Received Lne Signel Detector
Recetve Data
reg
Crto8ent
Signal Ground Comman RetUrn
reg Rrved (Testing)
Datas18nal
I 10
rate ct UnusedTnulSmitter signal Signed
element -f
timing (DTE-DCE) bull Tnt Mode 8eooundary~ 13 c
To8ent~
Figure 2a The RS232 pin configuration [81
Pin Number Line Line Pin Number
2 m m 2
3 RD RD 3
4 RTS RTS 4
5 CTS CTS 5
6 DSR---- DSR 6
7 Common 7
8 DCD DCD 8
20 DTR DTR 20
22 R1 R1 22
Figure 2b A Null Modem Configuration [8]
6
21 The Explanation For RS1Jl Pin Abbreviation
Hence is the detail ofeach line in DB9 and DB25 function
Clear to Send (CTS)
Data Carrier Detect (OCR)
Data Set Ready (DSR)
Data Terminal Ready (DTR)
Receive Data (RO)
Ring Indicator (RI)
Requested to Send (RTS)
Transmit Data (TD)
asserted (logic state 1) by DCE it is ready to receive data
logic state 1 whenever there is data link in progress
logic state 1 when DCE is ready to communicated withDTE
logic state 1 when DTE is ready to communicated withDCE
use by DCE to send data to DTE
logic 1 by DCE when a ring is detect
logic state 1 by DTE when it want to transmit data toDCE
Use by DTE to send data to DCE
Figure lc The Detail Explanation of Abbreviation [ 8]
22 UART
UART Universal Asynchronous Receiver Transmitter is a special hardware in RS232
serial interface It sometime called as Asynchronous Communication Element
Most of the new personal computer today is equip with 16450 and 16550 UART The
function ofUART chip is to convert the parallel data to a serial data format that enable a
serial communication between two computers The UART chip also uses to convert back
7
the serial bits to parallel bits format The operation of UART mostly control by one or
more register The process of read writes data to register are through input and output
ports Figure ld showing the address of a UART for COMI and COM4
The UART have FIFO or First in First out buffer FIFO bring the meaning as the first
data to enter the buffer are first to leave The function of buffer is to hold data temporary
before it was feed to the transmission medium The modem 16550A UART have16 bytes
FIFO This means 16 bytes can be writes to UART before anything was overwrite The
16550 UART was necessary for a high-speed communication under windows or
application running under window environment
Serial port Base Register Port Address
COM 1 3F8H COM2 2F8H COM3 3E8H COM3 2E8H
Figure ld The Serial Port Base Register Port [7 ]
23 Serial Communication
Serial communication is transmission of data over a serial interface one data bit at a time
In other word data are transfer through and forth over a single wire Therefore serial
communication is more cost effective than parallel communication RS232 is an example
for serial communication interface
24 Parallel Interface
Parallel communication is a way to sending more than one data at a time (normally eight
data bits) over to a parallel device or a Com Port For an example a computer will send
eight data bits of information to a parallel printer A very simple diagram of parallel
communication was present as Figure 2e The parallel interfaces require separated wire
8
------_------------__shyp
for sending separated data and therefor allowed faster and efficient data transmission On
the other hand to setting up a parallel communication network will be more costly than
serial communication network
1 Printer Interface
1 3 4 5 6 7 8
1 Computer Interface
2 3 4 5 6 7 8
Figure 2e A parallel Printer to Computer Interface [7 ]
25 Asynchronous and synchronous data
For two devices to communicate a way of synchronizing data must be set There are two
way ofdata formatting by using either asynchronous or synchronous
The synchronous operation is such a way that for each line data transmit it has a
separated clock to synchronous that data on a time of period For example data are
transfer once in each direction to and from the computer The synchronous data format
was show in figure 2f
While the asynchronous data is such a way that data are synchronous without clock
Each time the data are transmitting the receiver need to figure out how fast the data is
running The frame of asynchronous data has start and stops bit In another world the
frame always added with additional start and stop bit The asynchronous data format was
show in figure 2g
9
01100011100 o 1 1 1 11 0 0 0 0 001 0110 1 1 0
Unique Code
Continuous Block
Direction offlow
Figure 2f Synchronous data format I 8 ]
Start Stop d7 d6 d5 d4 d3 d2 dl dO Start
1 0 1 0 1 1 0 0I 1 I IMSB LSB
Start bit Stop bit1 Data-bits 1 I
r space mark mark space mark space mark mark space space
Serial Communication
Figure 2g Asynchronous Data Format Adopted form [8]
26 The Start Parity and Stop bits
For two machines to communicate to each other first thing both machines must agree on
the rate of speed for data transfer Second thing is the data must fonnatted for
synchronous or asynchronous operation Therefor for asynchronous operation the data
fonnatted in such a way that contains start and stop bit
271 Start bit
10
The TD line at interface device (Pin3) will go high when no data been transmit To start
transmit a data Transmit serial device will set TD line to low by means ofa start bit The
synchronous operation of DCE is waiting the TD line sign change from high bit to low
bit than DCE pauses half of a bit time and start sampling the incoming data until all the
character has been completely transmit To maintain synchronimtion DCE always
sampling the incoming data string at middle ofeach bit
272 Data bits
The data bits are the bits that contain character Nonnallyone character contains eight
bits Hence is the data bits showing character Amiddot 4tH
l start bit 41----shy Data bits j
shy
I t I Io 0 0 0 0 0
1 1deg1 1
Figure 2h The Data bits Format ( 7 ]
273 Parity bits
Four basic fonns ofparity bits are NONE EVEN ODD MARK and SPACE NONE use
for transmits a character without parity bit EVEN parity use to indicate by send logic 1
after a character if there is an odd number of logic 1 bit after a character data bit
Otherwise logic for EVEN parity goes to zero Odd parity will indicate by sending logic
1 after a data of a character bits if there is an even number of logic 1 after a characters
data bits Otherwise logic for ODD parity goes to zero Mark is logic 1 parity bit after a
data character and SPACE is logic zero after the data character
11
274 Stop bits
The stop bit indicated the end of a character The serial device was always send logic 1
for stop bit
28 Data Transmit and Receive Process
281 Transmit of a character
Several steps take before characters are transmitting from processor to modem
For an example communication between processor and 8251A USART
First the processor configures UART according to the communication protocol
Second an instruction was send to UART and set the flag TxEN Next The processor
was send the character to the data buffer ofUART Then this data buffer transfer the
character to transmit buffer for preparation for transmission Once data buffer was
complete transfer the character and ready to receive a new character the TXRDY flag
will set When processor automatically write in data buffer TXRDY flag automatically
reset
Next RTS (Ready to Send)pin output pin ofUART will alerted by modem that the bits
are about to transmit RTS pin for UART is tie together with modem RTS pin while the
modem realizes about to receive character from UART CTS pin will activated Then the
character was automatically transfer to modem The internal flag TxEMPTY will set
once the character was completely transmit from UART to modem
282 Receive of a character
The process of data receiving was also take several sequence First processor configures
UART according to standard protocol Then to receive a character the processor sends a
12
p
instruction to activated the RxE flag Next DART need to be alerted about the data going
to be transmitted DSR (Data Set Ready) will activated DSR pin of DART and modem
are tied together therefore when processor read this flags and realizes that the modem
has characters to be transmitted to DART Once DSR signal been set processor set DTR
(data terminal ready) to high And once DTR pin is asserted characters was
automatically transfer out from modem Once the characters is receive by DART it
formatted the data according to their start stop parity bits The RxRDY activated when a
character was completely receive
The bock diagram ofDART was show in ftgUre 2i
transmittedT~_B_r ~Mode Register
Transmit Register-~ I I data
I [_~~~J lt-~--r I
Receiver Register L~~~l-~~mmg =71 -_Rece~~I_v-e_r-B_-un_e=r=_-_ ~_romL--_
Devices and bullControl LogiC
l Internal Transmitter I Bus c-- ~ Clocking
--_______________rece_i_ve_r__lt=__-T Circuitary
Figure 2i USART Bloek Diagram [8 ]
28 COM Port setting
COM Port is the port that allowed computer to communicated with other device
such as modem or printer The standard personal computer normally has four
communications port COM 1 and COM 2 are assign for external port All the
13
PENGBARGAAN
Penulis ingin merakam penghargaan ikhlas kepada penyelia tesis EnNg Liang Yew dan
En Hushari Hj Zen di alas keperihatinan dan sokongan yang diberi sepanjang tempoh
penyelidikan tesis ini
Penghargaan kepada Pembantu Makmal En Zakaria atas sokongan beliau dalam
menjayakan projek tesis ini
Penghargaan juga diberi kepada sesiapa yang samada secara langsung atau tidak
langsung membantu dalam projek ini
III
i
ABSTRAK
Adalah menjadi satu masalah untuk mencapai maklumat di kawasan yang terpencil
Pembangunan rangkaian untuk kawasan tersebut biasanya bennasalah disebabkan beberapa
faktor Pertama kawasan tersebut adalah jauh dari rangkaian yang sediaada Kedua faktor
geographi kos pelaburan kos operasi serta pulangan yang rendah tidak menggalakan
syarikat telekomunikasi melabur di kawasan tersebut Ketiga tenaga mahir diperlukan kos
buruh mungkin tinggi Keempat lesen dari pihak berkuasa tempatan mungkin diperlukan
Kertas ini akan membincangkan satu pendekatan yang membolehkan individu berkomunikasi
secara tanpa wayar dengan menggunakan standard RS232 dan cabaya Laser sebagai
pembawa maklumat Perbincangan kertas ini merangkumi asas-asas rangkaian
telekommunikasi piawaian RS232 kaedah pemodulatan tanpa wayar analisa perisian dan
litar sistem tersebut Cadangan kertas ini ialah menggunakan RS232 Tranceiver yang
kedapatan dari Electronics Australia bertarikh October 1999 muka surat 56-61
IV
ABSTRACT
Is always a problem to access the data at a remote area The implementation on wireless
network for remote area is difficult due to certain reason First The places was isolated and
far from existing telecommunication access point Second the geographical factor high
investment cost of operation and maintenance low return will made a telecommunication
firm reluctant to put their investment in such area Third a highly skill personnel is need and
labour cost could be higher Forth the license from the authority concern might be required
Therefore this paper was to discuss a solution that allowed individual to communicate via
RS232 port using Laser light as communication medium This topics will cover the
fundamental of telecommunication network standard RS232 interface standard wireless
modulation technique Laser fundamental hardware and software analysis This paper is
designing to use RS232 Laser transceiver adapted from Electronics Australia dated Oct 1997
pg56-61
v
TABLE OF CONTENTS
Contents Pages
iiDEDICATION
ACKNOWLEDGEMENT iii
ABSTRAK iv
ABSTRACT v
TABLE OF CONTENTS vi
LIST OF ILLUSTRATION ix
Chapter 1 Wireless Communication An Overview
10 An Introduction 1 11 Wireless Network 1 12 Fundamental ofa Wireless Internet System 2 13 The Purpose of This Paper 2
CbapterZ RSZ3Z Interface amp Serial Communication
20 Overview 5 21 RS232 Pin Abbreviation 6 22 DART 7 23 Serial Communication 8 24 Parallel Communication 8 25 Asynchronous amp Synchronous Data 9 26 The Start Data Parity and Stop bit 10
261 Start bit 11 262 Data bits 11 263 Parity bits 11 264 Stop bit 12
27 Data Transmit amp Receive Process 12 281 Transmit ofa character 12 282 Receive ofa character 13
28 COM Port Setting 14
VI
Chapter 3 Laser as a Communication Medium
30 Fundamental of light 15 31 What is Laser 17 32 Characteristic ofa Laser Beam 19 33 Type ofLaser 20
331 Semiconductor Laser 20 332 Gas Lasers 20 333 Solid State Laser Nd YAG Laser 21
34 Light Modulation Scheme 22 35 Several Optical Modulation Techniques 25
351 Analog modulation 25 352 Pulse Modulation Technique 27
Chapter 4 Modulation Technique for Wireless System
40 Why Need Modulation 29 41 Amplitude Modulation 29 42 Frequency Modulation-AMPS 30 43 Generation ofFrequency Modula 31 44 Digital Modulation Technique 32 45 Frequency Shift Keying 32 46 Phase Shift Keying 35 47 Quadrature Phase Shift Keying 36 48 Offset Quadrature Phase Shift Keying 37 49 Minimum Shift Keying 39
Chapter 5 Laser Safety
50 Laser Beam Hazard 41 51 Safety Precaution amp Control Procedure 41 52 Class ofLaser 42
Chapter 6 System Design
60 Basic Overview 43 61 System Design 44 62 The Block Diagram 44 63 Function For Each Block 45 64 The Construction 45 65 Construction PCB 47 66 Observation 47 67 Testing
VII
p
Chapter 7 Software Analysis
70 Software Overview 50 71 Include Header File 53 72 Define The Setting 54 73 The Other Function 54 74 The Other Testing Program 55
ChapterS Conclusion
80 The Conclusion 58 81 The Future Work 58
APPENDIX A 60
REFERENCE 61
vm
LIST OF ILLUSTRATION
Figure Page
18 THE BLOCK DIAGRAM OF TYPICAL NETWORK 2
Ib CELCOMtrade DATA2GONETWORK
Ie SIMPLEST POINT-TO-POINT DATA COMMUNICATION VIA
2
RS232 LASER TRANSCEIVER 4
28 THE RS232 PIN CONFIGURATION 6
2b A NULL MODEM CONFIGURATION 6
2e DETAIL EXPLANATION OF RS232 PIN ABBREVIATION 7
2d THE SERIAL PORT BASE REGISTER 8
2e A PARALLEL PRINTER TO COMPUTER CONFIGURATION 9
2f SYNCHRONOUS DATA FORMAT 10
2g ASYNCBRONOUS DATA FORMAT 10
2h THE DATA BIT FORMAT 11
2i USART BLOCK DIAGRAM 13
3a ELECTRIC AND MAGNETIC FIELD IN PLANE ELECTROMAGNETIC WAVE 16
3b ILLUSTRATION OF ENERGY DIAGRAM FOR TWO LEVEL ENERGY SYSTEM ABSORPTION STIMULATED EMISSION 19 SPONTANEOUS EMISSION
3e SPATIAL COHERENT AT FOCUSING POINT 20
IX
po
3d EXCITATION OF GASEOUS LASER MEDIUM REFLECTION 21 OF PHOTON DURING STIMULATED EMISSION EXITING PHOTON IN LASER BEAM
SIGNAL (C) INTENSITY OF LIGHT
3e SCHEMATIC DIAGRAM FOR AN END PUMPED ND YAGLASER 22
3f THE ELECTROMAGNETIC SPECTRUM 23
3g AMPLITUDE MODULATION OF OPTICAL LIGHT BEAM 24
3h NON RETURN ZERO FORMAT 24
3i RETURN TO ZERO FORMAT 24
3j USING FM MODULATION TO MODULATED INTENSITY OF tiGHT (A) MASSAGE AMPUTUDE (B) FM MODULATION 25
4a AM SIGNAL MODULATION 30
4b FM SIGNAL MODULATION 31
4c FREQUENCY MODULATION 32
4d FSKFORMAT 33
4e FORMATION OF FSK SIGNAL 34
4f NON COHERENT DEMODULATION 35
4g COHERENT DEMODULATION 35
4h PSK WAVEFORM 36
4i THE GENERATION OF QPSK SIGNAL 37
4j OQPSK WAVEFORM (HALF SYMBOL OFFSET) 38
4k GENERATION ON OQPSK SIGNAL 39
41 GENERATION OF MSK WAVEFORM 40
4m OUTPUT WAVEFORM OF MSK SIGNAL 41
x
5a LASER WARNING LABEL 42
6a SIMPLE BLOCK DIAGRAM RS131 LASER COMMUNICATION SYSTEM 43
6b BLOCK DIAGRAM OF RS131 LASER TRANSCEIVER 44
6c SCHEMATIC OF TRANSCEIVER 45
6d PCB LAYOUT 46
6e DB9JUMPERING 48
7a THE HEADER FILE 54
7b THESETI1NG 55
7c BIOSCOM EXAMPLE 56
7d BIOS_SERIALCOM EXAMPLE 57
XI
CHAPTERt
WIRELESS COMMUNICATION AN OVERVIEW
to An Introduction
A communication occurs when there was an infonnation flow The word
telecommunication is derive from the Greek tele far of and communicare to share
[1] The communication is the process of transferring interpreting and processing
infonnation (data) among the people machines and place This process implies that we
need a sender a medium and a receiver to perform infonnation flow Therefore the
telecommunication is the process of exchanging the data of information in any useable
fonn in any natural delivery among two or more user by using radio wire and light and
other mechanical means
1t Wireless Network
Consider a cellular telephone system that provided coverage in a geographical
area as figure ta shown
To provide wireless communication within a region a Radio Base Station (RBS) must be
set up The Radio Base Station will perfonn the function as access point to the mobile
user and a connection with Mobile Switching Center A mobile user connected to base
station through Common Air Interface which can also called Handshaking ProtocoL [2]
The Radio Base Station will connect to mobile Switching Center through landline The
mobile switching center will provide connectivity to Public Switch Telephone Network
The PSTN Switching Center will provide connectivity to global network
The basic concept of a wireless network was to establishing the mobile user to a base
station followed by connection with mobile switch center and from mobile center
connected to global network
1
Mobile SWltchlna Center(MSC) or
Mobile Telephone SWItohlna omce Voice and Data link
(Landline or ~microwave)
Q ~ ~P-
PSTN
regRadio Link air interface
Figure la The Block Diagram of a Typical Wireless Network [ 2 ]
PSTN network and mobile network will connect by either fix-line or radio wave For the
fixmiddotline It will be twisted copper cable coaxial cable fiber optics cable For the radio
wave it either use microwave and satellite link The characteristic of a PSTN network is
the user was fix at one location while the mobile network allowed the user to move
within the coverage area The process of moving within the coverage area called
Roaming
12 Fundamental of a Wireless Intemet System
To accessing the internet a cellular user need to use a PCMCIA card with the adapter to
connected to laptop in the area where PSTN line was not accessible For example the
product of Celcom Data2Go for wireless data communication can have the following
function shy
e Electronic mail system
e Sending and receiving fax
2
bull Accessing Company database
bull Submit customer order
bull On-line information service
bull accessing Internet-surfing into Netscape
bull terminal mode- billinwregistration
The network ofData2Go by Celcomtradeas shown shy
Figure Ib Celcomtrade Data2Go Network 14 I
Software uses for this type ofnetwork are
bull Delrina WinFaxPro
bull Microsoft Mail
bull Netscape
bull Lotus Notes
13 The purpose of this paper
The main purpose of this project is to develop a useable technique that suitable for
sending data wireless via RS232 communication port The system component will consist
of a desktop computer that act as input device a standard RS232 interface a transceiver
for transmit and receive signal and a modify laser poniter The suggested system will be
3
set and tested in a point-to-point configuration As the figure show below the network
diagram stated shy
J -~HJj----tcooo ~ IEco~codl---=RS=232=--_~ Personal computer Signal RS232 Laser Transceiver RS2321aser Transceiver Personal computer
Figure lc The Simples point to point data communication via RS131laser transceiver
4
Cbapter2
RS-232 INTERFACE AND SERIAL COMMUNICATION
20 Overview
RS 232 Interface in a simple universal well knows data interface RS means
Recommended Standard1 The female connector attaches to Data Communication
Equipment and male connector attaches to Data Terminal Equipment Mostly today PCs
are equipped with two RS232 ports via COMI or COM2 The additional COM port
COM3 and COM4 required additional card
RS-232 defines 25-pin communication line Every line has their own function to
accessing data The configurations ofevery pin layout are show in figure 2a
Normally The ground signal refers to pin 7 Two computers can communicate by using a
null modem A null modem is a special made direct cable and connector It is functioning
like a modem but has limited transmission range Figure 2b illustrated the common
method to wiring a null modem Pin2 and pin3 are wire together and all the cables are
connect in such a way a modem simulated between two computers
The electrical characteristic define by RS232 as
(a) Total capacitance not less than 2500 pF
(b) (b) A binary high logic output lines is + 5to + 15 volts input lines is from +3
to + 15 volts
(c) A binary low logic output lines is from -5 to -15 volts input lines is from -3
to -15 volts
(d) output lines voltages -5 and +5 -3 and +3 volts for input lines are undefined
5
Shelld~ Secondary
tntnsmltted data Transmlttins
Signal element timlne (DCEoTE)
Secondary
Relcetver received data
Signal tlmlne(DCEoTE) Looak
Loopok Secondary
Request To8end
DTERudy
Rem_ Loopb8ok amp Signal Qua
Decmlctor RinS indicator
l reg
Transmitted Data
Request to Send
DCEReady
Rivedline 818nal Detector
Reserved (Testing)
Secondary Received Lne Signel Detector
Recetve Data
reg
Crto8ent
Signal Ground Comman RetUrn
reg Rrved (Testing)
Datas18nal
I 10
rate ct UnusedTnulSmitter signal Signed
element -f
timing (DTE-DCE) bull Tnt Mode 8eooundary~ 13 c
To8ent~
Figure 2a The RS232 pin configuration [81
Pin Number Line Line Pin Number
2 m m 2
3 RD RD 3
4 RTS RTS 4
5 CTS CTS 5
6 DSR---- DSR 6
7 Common 7
8 DCD DCD 8
20 DTR DTR 20
22 R1 R1 22
Figure 2b A Null Modem Configuration [8]
6
21 The Explanation For RS1Jl Pin Abbreviation
Hence is the detail ofeach line in DB9 and DB25 function
Clear to Send (CTS)
Data Carrier Detect (OCR)
Data Set Ready (DSR)
Data Terminal Ready (DTR)
Receive Data (RO)
Ring Indicator (RI)
Requested to Send (RTS)
Transmit Data (TD)
asserted (logic state 1) by DCE it is ready to receive data
logic state 1 whenever there is data link in progress
logic state 1 when DCE is ready to communicated withDTE
logic state 1 when DTE is ready to communicated withDCE
use by DCE to send data to DTE
logic 1 by DCE when a ring is detect
logic state 1 by DTE when it want to transmit data toDCE
Use by DTE to send data to DCE
Figure lc The Detail Explanation of Abbreviation [ 8]
22 UART
UART Universal Asynchronous Receiver Transmitter is a special hardware in RS232
serial interface It sometime called as Asynchronous Communication Element
Most of the new personal computer today is equip with 16450 and 16550 UART The
function ofUART chip is to convert the parallel data to a serial data format that enable a
serial communication between two computers The UART chip also uses to convert back
7
the serial bits to parallel bits format The operation of UART mostly control by one or
more register The process of read writes data to register are through input and output
ports Figure ld showing the address of a UART for COMI and COM4
The UART have FIFO or First in First out buffer FIFO bring the meaning as the first
data to enter the buffer are first to leave The function of buffer is to hold data temporary
before it was feed to the transmission medium The modem 16550A UART have16 bytes
FIFO This means 16 bytes can be writes to UART before anything was overwrite The
16550 UART was necessary for a high-speed communication under windows or
application running under window environment
Serial port Base Register Port Address
COM 1 3F8H COM2 2F8H COM3 3E8H COM3 2E8H
Figure ld The Serial Port Base Register Port [7 ]
23 Serial Communication
Serial communication is transmission of data over a serial interface one data bit at a time
In other word data are transfer through and forth over a single wire Therefore serial
communication is more cost effective than parallel communication RS232 is an example
for serial communication interface
24 Parallel Interface
Parallel communication is a way to sending more than one data at a time (normally eight
data bits) over to a parallel device or a Com Port For an example a computer will send
eight data bits of information to a parallel printer A very simple diagram of parallel
communication was present as Figure 2e The parallel interfaces require separated wire
8
------_------------__shyp
for sending separated data and therefor allowed faster and efficient data transmission On
the other hand to setting up a parallel communication network will be more costly than
serial communication network
1 Printer Interface
1 3 4 5 6 7 8
1 Computer Interface
2 3 4 5 6 7 8
Figure 2e A parallel Printer to Computer Interface [7 ]
25 Asynchronous and synchronous data
For two devices to communicate a way of synchronizing data must be set There are two
way ofdata formatting by using either asynchronous or synchronous
The synchronous operation is such a way that for each line data transmit it has a
separated clock to synchronous that data on a time of period For example data are
transfer once in each direction to and from the computer The synchronous data format
was show in figure 2f
While the asynchronous data is such a way that data are synchronous without clock
Each time the data are transmitting the receiver need to figure out how fast the data is
running The frame of asynchronous data has start and stops bit In another world the
frame always added with additional start and stop bit The asynchronous data format was
show in figure 2g
9
01100011100 o 1 1 1 11 0 0 0 0 001 0110 1 1 0
Unique Code
Continuous Block
Direction offlow
Figure 2f Synchronous data format I 8 ]
Start Stop d7 d6 d5 d4 d3 d2 dl dO Start
1 0 1 0 1 1 0 0I 1 I IMSB LSB
Start bit Stop bit1 Data-bits 1 I
r space mark mark space mark space mark mark space space
Serial Communication
Figure 2g Asynchronous Data Format Adopted form [8]
26 The Start Parity and Stop bits
For two machines to communicate to each other first thing both machines must agree on
the rate of speed for data transfer Second thing is the data must fonnatted for
synchronous or asynchronous operation Therefor for asynchronous operation the data
fonnatted in such a way that contains start and stop bit
271 Start bit
10
The TD line at interface device (Pin3) will go high when no data been transmit To start
transmit a data Transmit serial device will set TD line to low by means ofa start bit The
synchronous operation of DCE is waiting the TD line sign change from high bit to low
bit than DCE pauses half of a bit time and start sampling the incoming data until all the
character has been completely transmit To maintain synchronimtion DCE always
sampling the incoming data string at middle ofeach bit
272 Data bits
The data bits are the bits that contain character Nonnallyone character contains eight
bits Hence is the data bits showing character Amiddot 4tH
l start bit 41----shy Data bits j
shy
I t I Io 0 0 0 0 0
1 1deg1 1
Figure 2h The Data bits Format ( 7 ]
273 Parity bits
Four basic fonns ofparity bits are NONE EVEN ODD MARK and SPACE NONE use
for transmits a character without parity bit EVEN parity use to indicate by send logic 1
after a character if there is an odd number of logic 1 bit after a character data bit
Otherwise logic for EVEN parity goes to zero Odd parity will indicate by sending logic
1 after a data of a character bits if there is an even number of logic 1 after a characters
data bits Otherwise logic for ODD parity goes to zero Mark is logic 1 parity bit after a
data character and SPACE is logic zero after the data character
11
274 Stop bits
The stop bit indicated the end of a character The serial device was always send logic 1
for stop bit
28 Data Transmit and Receive Process
281 Transmit of a character
Several steps take before characters are transmitting from processor to modem
For an example communication between processor and 8251A USART
First the processor configures UART according to the communication protocol
Second an instruction was send to UART and set the flag TxEN Next The processor
was send the character to the data buffer ofUART Then this data buffer transfer the
character to transmit buffer for preparation for transmission Once data buffer was
complete transfer the character and ready to receive a new character the TXRDY flag
will set When processor automatically write in data buffer TXRDY flag automatically
reset
Next RTS (Ready to Send)pin output pin ofUART will alerted by modem that the bits
are about to transmit RTS pin for UART is tie together with modem RTS pin while the
modem realizes about to receive character from UART CTS pin will activated Then the
character was automatically transfer to modem The internal flag TxEMPTY will set
once the character was completely transmit from UART to modem
282 Receive of a character
The process of data receiving was also take several sequence First processor configures
UART according to standard protocol Then to receive a character the processor sends a
12
p
instruction to activated the RxE flag Next DART need to be alerted about the data going
to be transmitted DSR (Data Set Ready) will activated DSR pin of DART and modem
are tied together therefore when processor read this flags and realizes that the modem
has characters to be transmitted to DART Once DSR signal been set processor set DTR
(data terminal ready) to high And once DTR pin is asserted characters was
automatically transfer out from modem Once the characters is receive by DART it
formatted the data according to their start stop parity bits The RxRDY activated when a
character was completely receive
The bock diagram ofDART was show in ftgUre 2i
transmittedT~_B_r ~Mode Register
Transmit Register-~ I I data
I [_~~~J lt-~--r I
Receiver Register L~~~l-~~mmg =71 -_Rece~~I_v-e_r-B_-un_e=r=_-_ ~_romL--_
Devices and bullControl LogiC
l Internal Transmitter I Bus c-- ~ Clocking
--_______________rece_i_ve_r__lt=__-T Circuitary
Figure 2i USART Bloek Diagram [8 ]
28 COM Port setting
COM Port is the port that allowed computer to communicated with other device
such as modem or printer The standard personal computer normally has four
communications port COM 1 and COM 2 are assign for external port All the
13
ABSTRAK
Adalah menjadi satu masalah untuk mencapai maklumat di kawasan yang terpencil
Pembangunan rangkaian untuk kawasan tersebut biasanya bennasalah disebabkan beberapa
faktor Pertama kawasan tersebut adalah jauh dari rangkaian yang sediaada Kedua faktor
geographi kos pelaburan kos operasi serta pulangan yang rendah tidak menggalakan
syarikat telekomunikasi melabur di kawasan tersebut Ketiga tenaga mahir diperlukan kos
buruh mungkin tinggi Keempat lesen dari pihak berkuasa tempatan mungkin diperlukan
Kertas ini akan membincangkan satu pendekatan yang membolehkan individu berkomunikasi
secara tanpa wayar dengan menggunakan standard RS232 dan cabaya Laser sebagai
pembawa maklumat Perbincangan kertas ini merangkumi asas-asas rangkaian
telekommunikasi piawaian RS232 kaedah pemodulatan tanpa wayar analisa perisian dan
litar sistem tersebut Cadangan kertas ini ialah menggunakan RS232 Tranceiver yang
kedapatan dari Electronics Australia bertarikh October 1999 muka surat 56-61
IV
ABSTRACT
Is always a problem to access the data at a remote area The implementation on wireless
network for remote area is difficult due to certain reason First The places was isolated and
far from existing telecommunication access point Second the geographical factor high
investment cost of operation and maintenance low return will made a telecommunication
firm reluctant to put their investment in such area Third a highly skill personnel is need and
labour cost could be higher Forth the license from the authority concern might be required
Therefore this paper was to discuss a solution that allowed individual to communicate via
RS232 port using Laser light as communication medium This topics will cover the
fundamental of telecommunication network standard RS232 interface standard wireless
modulation technique Laser fundamental hardware and software analysis This paper is
designing to use RS232 Laser transceiver adapted from Electronics Australia dated Oct 1997
pg56-61
v
TABLE OF CONTENTS
Contents Pages
iiDEDICATION
ACKNOWLEDGEMENT iii
ABSTRAK iv
ABSTRACT v
TABLE OF CONTENTS vi
LIST OF ILLUSTRATION ix
Chapter 1 Wireless Communication An Overview
10 An Introduction 1 11 Wireless Network 1 12 Fundamental ofa Wireless Internet System 2 13 The Purpose of This Paper 2
CbapterZ RSZ3Z Interface amp Serial Communication
20 Overview 5 21 RS232 Pin Abbreviation 6 22 DART 7 23 Serial Communication 8 24 Parallel Communication 8 25 Asynchronous amp Synchronous Data 9 26 The Start Data Parity and Stop bit 10
261 Start bit 11 262 Data bits 11 263 Parity bits 11 264 Stop bit 12
27 Data Transmit amp Receive Process 12 281 Transmit ofa character 12 282 Receive ofa character 13
28 COM Port Setting 14
VI
Chapter 3 Laser as a Communication Medium
30 Fundamental of light 15 31 What is Laser 17 32 Characteristic ofa Laser Beam 19 33 Type ofLaser 20
331 Semiconductor Laser 20 332 Gas Lasers 20 333 Solid State Laser Nd YAG Laser 21
34 Light Modulation Scheme 22 35 Several Optical Modulation Techniques 25
351 Analog modulation 25 352 Pulse Modulation Technique 27
Chapter 4 Modulation Technique for Wireless System
40 Why Need Modulation 29 41 Amplitude Modulation 29 42 Frequency Modulation-AMPS 30 43 Generation ofFrequency Modula 31 44 Digital Modulation Technique 32 45 Frequency Shift Keying 32 46 Phase Shift Keying 35 47 Quadrature Phase Shift Keying 36 48 Offset Quadrature Phase Shift Keying 37 49 Minimum Shift Keying 39
Chapter 5 Laser Safety
50 Laser Beam Hazard 41 51 Safety Precaution amp Control Procedure 41 52 Class ofLaser 42
Chapter 6 System Design
60 Basic Overview 43 61 System Design 44 62 The Block Diagram 44 63 Function For Each Block 45 64 The Construction 45 65 Construction PCB 47 66 Observation 47 67 Testing
VII
p
Chapter 7 Software Analysis
70 Software Overview 50 71 Include Header File 53 72 Define The Setting 54 73 The Other Function 54 74 The Other Testing Program 55
ChapterS Conclusion
80 The Conclusion 58 81 The Future Work 58
APPENDIX A 60
REFERENCE 61
vm
LIST OF ILLUSTRATION
Figure Page
18 THE BLOCK DIAGRAM OF TYPICAL NETWORK 2
Ib CELCOMtrade DATA2GONETWORK
Ie SIMPLEST POINT-TO-POINT DATA COMMUNICATION VIA
2
RS232 LASER TRANSCEIVER 4
28 THE RS232 PIN CONFIGURATION 6
2b A NULL MODEM CONFIGURATION 6
2e DETAIL EXPLANATION OF RS232 PIN ABBREVIATION 7
2d THE SERIAL PORT BASE REGISTER 8
2e A PARALLEL PRINTER TO COMPUTER CONFIGURATION 9
2f SYNCHRONOUS DATA FORMAT 10
2g ASYNCBRONOUS DATA FORMAT 10
2h THE DATA BIT FORMAT 11
2i USART BLOCK DIAGRAM 13
3a ELECTRIC AND MAGNETIC FIELD IN PLANE ELECTROMAGNETIC WAVE 16
3b ILLUSTRATION OF ENERGY DIAGRAM FOR TWO LEVEL ENERGY SYSTEM ABSORPTION STIMULATED EMISSION 19 SPONTANEOUS EMISSION
3e SPATIAL COHERENT AT FOCUSING POINT 20
IX
po
3d EXCITATION OF GASEOUS LASER MEDIUM REFLECTION 21 OF PHOTON DURING STIMULATED EMISSION EXITING PHOTON IN LASER BEAM
SIGNAL (C) INTENSITY OF LIGHT
3e SCHEMATIC DIAGRAM FOR AN END PUMPED ND YAGLASER 22
3f THE ELECTROMAGNETIC SPECTRUM 23
3g AMPLITUDE MODULATION OF OPTICAL LIGHT BEAM 24
3h NON RETURN ZERO FORMAT 24
3i RETURN TO ZERO FORMAT 24
3j USING FM MODULATION TO MODULATED INTENSITY OF tiGHT (A) MASSAGE AMPUTUDE (B) FM MODULATION 25
4a AM SIGNAL MODULATION 30
4b FM SIGNAL MODULATION 31
4c FREQUENCY MODULATION 32
4d FSKFORMAT 33
4e FORMATION OF FSK SIGNAL 34
4f NON COHERENT DEMODULATION 35
4g COHERENT DEMODULATION 35
4h PSK WAVEFORM 36
4i THE GENERATION OF QPSK SIGNAL 37
4j OQPSK WAVEFORM (HALF SYMBOL OFFSET) 38
4k GENERATION ON OQPSK SIGNAL 39
41 GENERATION OF MSK WAVEFORM 40
4m OUTPUT WAVEFORM OF MSK SIGNAL 41
x
5a LASER WARNING LABEL 42
6a SIMPLE BLOCK DIAGRAM RS131 LASER COMMUNICATION SYSTEM 43
6b BLOCK DIAGRAM OF RS131 LASER TRANSCEIVER 44
6c SCHEMATIC OF TRANSCEIVER 45
6d PCB LAYOUT 46
6e DB9JUMPERING 48
7a THE HEADER FILE 54
7b THESETI1NG 55
7c BIOSCOM EXAMPLE 56
7d BIOS_SERIALCOM EXAMPLE 57
XI
CHAPTERt
WIRELESS COMMUNICATION AN OVERVIEW
to An Introduction
A communication occurs when there was an infonnation flow The word
telecommunication is derive from the Greek tele far of and communicare to share
[1] The communication is the process of transferring interpreting and processing
infonnation (data) among the people machines and place This process implies that we
need a sender a medium and a receiver to perform infonnation flow Therefore the
telecommunication is the process of exchanging the data of information in any useable
fonn in any natural delivery among two or more user by using radio wire and light and
other mechanical means
1t Wireless Network
Consider a cellular telephone system that provided coverage in a geographical
area as figure ta shown
To provide wireless communication within a region a Radio Base Station (RBS) must be
set up The Radio Base Station will perfonn the function as access point to the mobile
user and a connection with Mobile Switching Center A mobile user connected to base
station through Common Air Interface which can also called Handshaking ProtocoL [2]
The Radio Base Station will connect to mobile Switching Center through landline The
mobile switching center will provide connectivity to Public Switch Telephone Network
The PSTN Switching Center will provide connectivity to global network
The basic concept of a wireless network was to establishing the mobile user to a base
station followed by connection with mobile switch center and from mobile center
connected to global network
1
Mobile SWltchlna Center(MSC) or
Mobile Telephone SWItohlna omce Voice and Data link
(Landline or ~microwave)
Q ~ ~P-
PSTN
regRadio Link air interface
Figure la The Block Diagram of a Typical Wireless Network [ 2 ]
PSTN network and mobile network will connect by either fix-line or radio wave For the
fixmiddotline It will be twisted copper cable coaxial cable fiber optics cable For the radio
wave it either use microwave and satellite link The characteristic of a PSTN network is
the user was fix at one location while the mobile network allowed the user to move
within the coverage area The process of moving within the coverage area called
Roaming
12 Fundamental of a Wireless Intemet System
To accessing the internet a cellular user need to use a PCMCIA card with the adapter to
connected to laptop in the area where PSTN line was not accessible For example the
product of Celcom Data2Go for wireless data communication can have the following
function shy
e Electronic mail system
e Sending and receiving fax
2
bull Accessing Company database
bull Submit customer order
bull On-line information service
bull accessing Internet-surfing into Netscape
bull terminal mode- billinwregistration
The network ofData2Go by Celcomtradeas shown shy
Figure Ib Celcomtrade Data2Go Network 14 I
Software uses for this type ofnetwork are
bull Delrina WinFaxPro
bull Microsoft Mail
bull Netscape
bull Lotus Notes
13 The purpose of this paper
The main purpose of this project is to develop a useable technique that suitable for
sending data wireless via RS232 communication port The system component will consist
of a desktop computer that act as input device a standard RS232 interface a transceiver
for transmit and receive signal and a modify laser poniter The suggested system will be
3
set and tested in a point-to-point configuration As the figure show below the network
diagram stated shy
J -~HJj----tcooo ~ IEco~codl---=RS=232=--_~ Personal computer Signal RS232 Laser Transceiver RS2321aser Transceiver Personal computer
Figure lc The Simples point to point data communication via RS131laser transceiver
4
Cbapter2
RS-232 INTERFACE AND SERIAL COMMUNICATION
20 Overview
RS 232 Interface in a simple universal well knows data interface RS means
Recommended Standard1 The female connector attaches to Data Communication
Equipment and male connector attaches to Data Terminal Equipment Mostly today PCs
are equipped with two RS232 ports via COMI or COM2 The additional COM port
COM3 and COM4 required additional card
RS-232 defines 25-pin communication line Every line has their own function to
accessing data The configurations ofevery pin layout are show in figure 2a
Normally The ground signal refers to pin 7 Two computers can communicate by using a
null modem A null modem is a special made direct cable and connector It is functioning
like a modem but has limited transmission range Figure 2b illustrated the common
method to wiring a null modem Pin2 and pin3 are wire together and all the cables are
connect in such a way a modem simulated between two computers
The electrical characteristic define by RS232 as
(a) Total capacitance not less than 2500 pF
(b) (b) A binary high logic output lines is + 5to + 15 volts input lines is from +3
to + 15 volts
(c) A binary low logic output lines is from -5 to -15 volts input lines is from -3
to -15 volts
(d) output lines voltages -5 and +5 -3 and +3 volts for input lines are undefined
5
Shelld~ Secondary
tntnsmltted data Transmlttins
Signal element timlne (DCEoTE)
Secondary
Relcetver received data
Signal tlmlne(DCEoTE) Looak
Loopok Secondary
Request To8end
DTERudy
Rem_ Loopb8ok amp Signal Qua
Decmlctor RinS indicator
l reg
Transmitted Data
Request to Send
DCEReady
Rivedline 818nal Detector
Reserved (Testing)
Secondary Received Lne Signel Detector
Recetve Data
reg
Crto8ent
Signal Ground Comman RetUrn
reg Rrved (Testing)
Datas18nal
I 10
rate ct UnusedTnulSmitter signal Signed
element -f
timing (DTE-DCE) bull Tnt Mode 8eooundary~ 13 c
To8ent~
Figure 2a The RS232 pin configuration [81
Pin Number Line Line Pin Number
2 m m 2
3 RD RD 3
4 RTS RTS 4
5 CTS CTS 5
6 DSR---- DSR 6
7 Common 7
8 DCD DCD 8
20 DTR DTR 20
22 R1 R1 22
Figure 2b A Null Modem Configuration [8]
6
21 The Explanation For RS1Jl Pin Abbreviation
Hence is the detail ofeach line in DB9 and DB25 function
Clear to Send (CTS)
Data Carrier Detect (OCR)
Data Set Ready (DSR)
Data Terminal Ready (DTR)
Receive Data (RO)
Ring Indicator (RI)
Requested to Send (RTS)
Transmit Data (TD)
asserted (logic state 1) by DCE it is ready to receive data
logic state 1 whenever there is data link in progress
logic state 1 when DCE is ready to communicated withDTE
logic state 1 when DTE is ready to communicated withDCE
use by DCE to send data to DTE
logic 1 by DCE when a ring is detect
logic state 1 by DTE when it want to transmit data toDCE
Use by DTE to send data to DCE
Figure lc The Detail Explanation of Abbreviation [ 8]
22 UART
UART Universal Asynchronous Receiver Transmitter is a special hardware in RS232
serial interface It sometime called as Asynchronous Communication Element
Most of the new personal computer today is equip with 16450 and 16550 UART The
function ofUART chip is to convert the parallel data to a serial data format that enable a
serial communication between two computers The UART chip also uses to convert back
7
the serial bits to parallel bits format The operation of UART mostly control by one or
more register The process of read writes data to register are through input and output
ports Figure ld showing the address of a UART for COMI and COM4
The UART have FIFO or First in First out buffer FIFO bring the meaning as the first
data to enter the buffer are first to leave The function of buffer is to hold data temporary
before it was feed to the transmission medium The modem 16550A UART have16 bytes
FIFO This means 16 bytes can be writes to UART before anything was overwrite The
16550 UART was necessary for a high-speed communication under windows or
application running under window environment
Serial port Base Register Port Address
COM 1 3F8H COM2 2F8H COM3 3E8H COM3 2E8H
Figure ld The Serial Port Base Register Port [7 ]
23 Serial Communication
Serial communication is transmission of data over a serial interface one data bit at a time
In other word data are transfer through and forth over a single wire Therefore serial
communication is more cost effective than parallel communication RS232 is an example
for serial communication interface
24 Parallel Interface
Parallel communication is a way to sending more than one data at a time (normally eight
data bits) over to a parallel device or a Com Port For an example a computer will send
eight data bits of information to a parallel printer A very simple diagram of parallel
communication was present as Figure 2e The parallel interfaces require separated wire
8
------_------------__shyp
for sending separated data and therefor allowed faster and efficient data transmission On
the other hand to setting up a parallel communication network will be more costly than
serial communication network
1 Printer Interface
1 3 4 5 6 7 8
1 Computer Interface
2 3 4 5 6 7 8
Figure 2e A parallel Printer to Computer Interface [7 ]
25 Asynchronous and synchronous data
For two devices to communicate a way of synchronizing data must be set There are two
way ofdata formatting by using either asynchronous or synchronous
The synchronous operation is such a way that for each line data transmit it has a
separated clock to synchronous that data on a time of period For example data are
transfer once in each direction to and from the computer The synchronous data format
was show in figure 2f
While the asynchronous data is such a way that data are synchronous without clock
Each time the data are transmitting the receiver need to figure out how fast the data is
running The frame of asynchronous data has start and stops bit In another world the
frame always added with additional start and stop bit The asynchronous data format was
show in figure 2g
9
01100011100 o 1 1 1 11 0 0 0 0 001 0110 1 1 0
Unique Code
Continuous Block
Direction offlow
Figure 2f Synchronous data format I 8 ]
Start Stop d7 d6 d5 d4 d3 d2 dl dO Start
1 0 1 0 1 1 0 0I 1 I IMSB LSB
Start bit Stop bit1 Data-bits 1 I
r space mark mark space mark space mark mark space space
Serial Communication
Figure 2g Asynchronous Data Format Adopted form [8]
26 The Start Parity and Stop bits
For two machines to communicate to each other first thing both machines must agree on
the rate of speed for data transfer Second thing is the data must fonnatted for
synchronous or asynchronous operation Therefor for asynchronous operation the data
fonnatted in such a way that contains start and stop bit
271 Start bit
10
The TD line at interface device (Pin3) will go high when no data been transmit To start
transmit a data Transmit serial device will set TD line to low by means ofa start bit The
synchronous operation of DCE is waiting the TD line sign change from high bit to low
bit than DCE pauses half of a bit time and start sampling the incoming data until all the
character has been completely transmit To maintain synchronimtion DCE always
sampling the incoming data string at middle ofeach bit
272 Data bits
The data bits are the bits that contain character Nonnallyone character contains eight
bits Hence is the data bits showing character Amiddot 4tH
l start bit 41----shy Data bits j
shy
I t I Io 0 0 0 0 0
1 1deg1 1
Figure 2h The Data bits Format ( 7 ]
273 Parity bits
Four basic fonns ofparity bits are NONE EVEN ODD MARK and SPACE NONE use
for transmits a character without parity bit EVEN parity use to indicate by send logic 1
after a character if there is an odd number of logic 1 bit after a character data bit
Otherwise logic for EVEN parity goes to zero Odd parity will indicate by sending logic
1 after a data of a character bits if there is an even number of logic 1 after a characters
data bits Otherwise logic for ODD parity goes to zero Mark is logic 1 parity bit after a
data character and SPACE is logic zero after the data character
11
274 Stop bits
The stop bit indicated the end of a character The serial device was always send logic 1
for stop bit
28 Data Transmit and Receive Process
281 Transmit of a character
Several steps take before characters are transmitting from processor to modem
For an example communication between processor and 8251A USART
First the processor configures UART according to the communication protocol
Second an instruction was send to UART and set the flag TxEN Next The processor
was send the character to the data buffer ofUART Then this data buffer transfer the
character to transmit buffer for preparation for transmission Once data buffer was
complete transfer the character and ready to receive a new character the TXRDY flag
will set When processor automatically write in data buffer TXRDY flag automatically
reset
Next RTS (Ready to Send)pin output pin ofUART will alerted by modem that the bits
are about to transmit RTS pin for UART is tie together with modem RTS pin while the
modem realizes about to receive character from UART CTS pin will activated Then the
character was automatically transfer to modem The internal flag TxEMPTY will set
once the character was completely transmit from UART to modem
282 Receive of a character
The process of data receiving was also take several sequence First processor configures
UART according to standard protocol Then to receive a character the processor sends a
12
p
instruction to activated the RxE flag Next DART need to be alerted about the data going
to be transmitted DSR (Data Set Ready) will activated DSR pin of DART and modem
are tied together therefore when processor read this flags and realizes that the modem
has characters to be transmitted to DART Once DSR signal been set processor set DTR
(data terminal ready) to high And once DTR pin is asserted characters was
automatically transfer out from modem Once the characters is receive by DART it
formatted the data according to their start stop parity bits The RxRDY activated when a
character was completely receive
The bock diagram ofDART was show in ftgUre 2i
transmittedT~_B_r ~Mode Register
Transmit Register-~ I I data
I [_~~~J lt-~--r I
Receiver Register L~~~l-~~mmg =71 -_Rece~~I_v-e_r-B_-un_e=r=_-_ ~_romL--_
Devices and bullControl LogiC
l Internal Transmitter I Bus c-- ~ Clocking
--_______________rece_i_ve_r__lt=__-T Circuitary
Figure 2i USART Bloek Diagram [8 ]
28 COM Port setting
COM Port is the port that allowed computer to communicated with other device
such as modem or printer The standard personal computer normally has four
communications port COM 1 and COM 2 are assign for external port All the
13
ABSTRACT
Is always a problem to access the data at a remote area The implementation on wireless
network for remote area is difficult due to certain reason First The places was isolated and
far from existing telecommunication access point Second the geographical factor high
investment cost of operation and maintenance low return will made a telecommunication
firm reluctant to put their investment in such area Third a highly skill personnel is need and
labour cost could be higher Forth the license from the authority concern might be required
Therefore this paper was to discuss a solution that allowed individual to communicate via
RS232 port using Laser light as communication medium This topics will cover the
fundamental of telecommunication network standard RS232 interface standard wireless
modulation technique Laser fundamental hardware and software analysis This paper is
designing to use RS232 Laser transceiver adapted from Electronics Australia dated Oct 1997
pg56-61
v
TABLE OF CONTENTS
Contents Pages
iiDEDICATION
ACKNOWLEDGEMENT iii
ABSTRAK iv
ABSTRACT v
TABLE OF CONTENTS vi
LIST OF ILLUSTRATION ix
Chapter 1 Wireless Communication An Overview
10 An Introduction 1 11 Wireless Network 1 12 Fundamental ofa Wireless Internet System 2 13 The Purpose of This Paper 2
CbapterZ RSZ3Z Interface amp Serial Communication
20 Overview 5 21 RS232 Pin Abbreviation 6 22 DART 7 23 Serial Communication 8 24 Parallel Communication 8 25 Asynchronous amp Synchronous Data 9 26 The Start Data Parity and Stop bit 10
261 Start bit 11 262 Data bits 11 263 Parity bits 11 264 Stop bit 12
27 Data Transmit amp Receive Process 12 281 Transmit ofa character 12 282 Receive ofa character 13
28 COM Port Setting 14
VI
Chapter 3 Laser as a Communication Medium
30 Fundamental of light 15 31 What is Laser 17 32 Characteristic ofa Laser Beam 19 33 Type ofLaser 20
331 Semiconductor Laser 20 332 Gas Lasers 20 333 Solid State Laser Nd YAG Laser 21
34 Light Modulation Scheme 22 35 Several Optical Modulation Techniques 25
351 Analog modulation 25 352 Pulse Modulation Technique 27
Chapter 4 Modulation Technique for Wireless System
40 Why Need Modulation 29 41 Amplitude Modulation 29 42 Frequency Modulation-AMPS 30 43 Generation ofFrequency Modula 31 44 Digital Modulation Technique 32 45 Frequency Shift Keying 32 46 Phase Shift Keying 35 47 Quadrature Phase Shift Keying 36 48 Offset Quadrature Phase Shift Keying 37 49 Minimum Shift Keying 39
Chapter 5 Laser Safety
50 Laser Beam Hazard 41 51 Safety Precaution amp Control Procedure 41 52 Class ofLaser 42
Chapter 6 System Design
60 Basic Overview 43 61 System Design 44 62 The Block Diagram 44 63 Function For Each Block 45 64 The Construction 45 65 Construction PCB 47 66 Observation 47 67 Testing
VII
p
Chapter 7 Software Analysis
70 Software Overview 50 71 Include Header File 53 72 Define The Setting 54 73 The Other Function 54 74 The Other Testing Program 55
ChapterS Conclusion
80 The Conclusion 58 81 The Future Work 58
APPENDIX A 60
REFERENCE 61
vm
LIST OF ILLUSTRATION
Figure Page
18 THE BLOCK DIAGRAM OF TYPICAL NETWORK 2
Ib CELCOMtrade DATA2GONETWORK
Ie SIMPLEST POINT-TO-POINT DATA COMMUNICATION VIA
2
RS232 LASER TRANSCEIVER 4
28 THE RS232 PIN CONFIGURATION 6
2b A NULL MODEM CONFIGURATION 6
2e DETAIL EXPLANATION OF RS232 PIN ABBREVIATION 7
2d THE SERIAL PORT BASE REGISTER 8
2e A PARALLEL PRINTER TO COMPUTER CONFIGURATION 9
2f SYNCHRONOUS DATA FORMAT 10
2g ASYNCBRONOUS DATA FORMAT 10
2h THE DATA BIT FORMAT 11
2i USART BLOCK DIAGRAM 13
3a ELECTRIC AND MAGNETIC FIELD IN PLANE ELECTROMAGNETIC WAVE 16
3b ILLUSTRATION OF ENERGY DIAGRAM FOR TWO LEVEL ENERGY SYSTEM ABSORPTION STIMULATED EMISSION 19 SPONTANEOUS EMISSION
3e SPATIAL COHERENT AT FOCUSING POINT 20
IX
po
3d EXCITATION OF GASEOUS LASER MEDIUM REFLECTION 21 OF PHOTON DURING STIMULATED EMISSION EXITING PHOTON IN LASER BEAM
SIGNAL (C) INTENSITY OF LIGHT
3e SCHEMATIC DIAGRAM FOR AN END PUMPED ND YAGLASER 22
3f THE ELECTROMAGNETIC SPECTRUM 23
3g AMPLITUDE MODULATION OF OPTICAL LIGHT BEAM 24
3h NON RETURN ZERO FORMAT 24
3i RETURN TO ZERO FORMAT 24
3j USING FM MODULATION TO MODULATED INTENSITY OF tiGHT (A) MASSAGE AMPUTUDE (B) FM MODULATION 25
4a AM SIGNAL MODULATION 30
4b FM SIGNAL MODULATION 31
4c FREQUENCY MODULATION 32
4d FSKFORMAT 33
4e FORMATION OF FSK SIGNAL 34
4f NON COHERENT DEMODULATION 35
4g COHERENT DEMODULATION 35
4h PSK WAVEFORM 36
4i THE GENERATION OF QPSK SIGNAL 37
4j OQPSK WAVEFORM (HALF SYMBOL OFFSET) 38
4k GENERATION ON OQPSK SIGNAL 39
41 GENERATION OF MSK WAVEFORM 40
4m OUTPUT WAVEFORM OF MSK SIGNAL 41
x
5a LASER WARNING LABEL 42
6a SIMPLE BLOCK DIAGRAM RS131 LASER COMMUNICATION SYSTEM 43
6b BLOCK DIAGRAM OF RS131 LASER TRANSCEIVER 44
6c SCHEMATIC OF TRANSCEIVER 45
6d PCB LAYOUT 46
6e DB9JUMPERING 48
7a THE HEADER FILE 54
7b THESETI1NG 55
7c BIOSCOM EXAMPLE 56
7d BIOS_SERIALCOM EXAMPLE 57
XI
CHAPTERt
WIRELESS COMMUNICATION AN OVERVIEW
to An Introduction
A communication occurs when there was an infonnation flow The word
telecommunication is derive from the Greek tele far of and communicare to share
[1] The communication is the process of transferring interpreting and processing
infonnation (data) among the people machines and place This process implies that we
need a sender a medium and a receiver to perform infonnation flow Therefore the
telecommunication is the process of exchanging the data of information in any useable
fonn in any natural delivery among two or more user by using radio wire and light and
other mechanical means
1t Wireless Network
Consider a cellular telephone system that provided coverage in a geographical
area as figure ta shown
To provide wireless communication within a region a Radio Base Station (RBS) must be
set up The Radio Base Station will perfonn the function as access point to the mobile
user and a connection with Mobile Switching Center A mobile user connected to base
station through Common Air Interface which can also called Handshaking ProtocoL [2]
The Radio Base Station will connect to mobile Switching Center through landline The
mobile switching center will provide connectivity to Public Switch Telephone Network
The PSTN Switching Center will provide connectivity to global network
The basic concept of a wireless network was to establishing the mobile user to a base
station followed by connection with mobile switch center and from mobile center
connected to global network
1
Mobile SWltchlna Center(MSC) or
Mobile Telephone SWItohlna omce Voice and Data link
(Landline or ~microwave)
Q ~ ~P-
PSTN
regRadio Link air interface
Figure la The Block Diagram of a Typical Wireless Network [ 2 ]
PSTN network and mobile network will connect by either fix-line or radio wave For the
fixmiddotline It will be twisted copper cable coaxial cable fiber optics cable For the radio
wave it either use microwave and satellite link The characteristic of a PSTN network is
the user was fix at one location while the mobile network allowed the user to move
within the coverage area The process of moving within the coverage area called
Roaming
12 Fundamental of a Wireless Intemet System
To accessing the internet a cellular user need to use a PCMCIA card with the adapter to
connected to laptop in the area where PSTN line was not accessible For example the
product of Celcom Data2Go for wireless data communication can have the following
function shy
e Electronic mail system
e Sending and receiving fax
2
bull Accessing Company database
bull Submit customer order
bull On-line information service
bull accessing Internet-surfing into Netscape
bull terminal mode- billinwregistration
The network ofData2Go by Celcomtradeas shown shy
Figure Ib Celcomtrade Data2Go Network 14 I
Software uses for this type ofnetwork are
bull Delrina WinFaxPro
bull Microsoft Mail
bull Netscape
bull Lotus Notes
13 The purpose of this paper
The main purpose of this project is to develop a useable technique that suitable for
sending data wireless via RS232 communication port The system component will consist
of a desktop computer that act as input device a standard RS232 interface a transceiver
for transmit and receive signal and a modify laser poniter The suggested system will be
3
set and tested in a point-to-point configuration As the figure show below the network
diagram stated shy
J -~HJj----tcooo ~ IEco~codl---=RS=232=--_~ Personal computer Signal RS232 Laser Transceiver RS2321aser Transceiver Personal computer
Figure lc The Simples point to point data communication via RS131laser transceiver
4
Cbapter2
RS-232 INTERFACE AND SERIAL COMMUNICATION
20 Overview
RS 232 Interface in a simple universal well knows data interface RS means
Recommended Standard1 The female connector attaches to Data Communication
Equipment and male connector attaches to Data Terminal Equipment Mostly today PCs
are equipped with two RS232 ports via COMI or COM2 The additional COM port
COM3 and COM4 required additional card
RS-232 defines 25-pin communication line Every line has their own function to
accessing data The configurations ofevery pin layout are show in figure 2a
Normally The ground signal refers to pin 7 Two computers can communicate by using a
null modem A null modem is a special made direct cable and connector It is functioning
like a modem but has limited transmission range Figure 2b illustrated the common
method to wiring a null modem Pin2 and pin3 are wire together and all the cables are
connect in such a way a modem simulated between two computers
The electrical characteristic define by RS232 as
(a) Total capacitance not less than 2500 pF
(b) (b) A binary high logic output lines is + 5to + 15 volts input lines is from +3
to + 15 volts
(c) A binary low logic output lines is from -5 to -15 volts input lines is from -3
to -15 volts
(d) output lines voltages -5 and +5 -3 and +3 volts for input lines are undefined
5
Shelld~ Secondary
tntnsmltted data Transmlttins
Signal element timlne (DCEoTE)
Secondary
Relcetver received data
Signal tlmlne(DCEoTE) Looak
Loopok Secondary
Request To8end
DTERudy
Rem_ Loopb8ok amp Signal Qua
Decmlctor RinS indicator
l reg
Transmitted Data
Request to Send
DCEReady
Rivedline 818nal Detector
Reserved (Testing)
Secondary Received Lne Signel Detector
Recetve Data
reg
Crto8ent
Signal Ground Comman RetUrn
reg Rrved (Testing)
Datas18nal
I 10
rate ct UnusedTnulSmitter signal Signed
element -f
timing (DTE-DCE) bull Tnt Mode 8eooundary~ 13 c
To8ent~
Figure 2a The RS232 pin configuration [81
Pin Number Line Line Pin Number
2 m m 2
3 RD RD 3
4 RTS RTS 4
5 CTS CTS 5
6 DSR---- DSR 6
7 Common 7
8 DCD DCD 8
20 DTR DTR 20
22 R1 R1 22
Figure 2b A Null Modem Configuration [8]
6
21 The Explanation For RS1Jl Pin Abbreviation
Hence is the detail ofeach line in DB9 and DB25 function
Clear to Send (CTS)
Data Carrier Detect (OCR)
Data Set Ready (DSR)
Data Terminal Ready (DTR)
Receive Data (RO)
Ring Indicator (RI)
Requested to Send (RTS)
Transmit Data (TD)
asserted (logic state 1) by DCE it is ready to receive data
logic state 1 whenever there is data link in progress
logic state 1 when DCE is ready to communicated withDTE
logic state 1 when DTE is ready to communicated withDCE
use by DCE to send data to DTE
logic 1 by DCE when a ring is detect
logic state 1 by DTE when it want to transmit data toDCE
Use by DTE to send data to DCE
Figure lc The Detail Explanation of Abbreviation [ 8]
22 UART
UART Universal Asynchronous Receiver Transmitter is a special hardware in RS232
serial interface It sometime called as Asynchronous Communication Element
Most of the new personal computer today is equip with 16450 and 16550 UART The
function ofUART chip is to convert the parallel data to a serial data format that enable a
serial communication between two computers The UART chip also uses to convert back
7
the serial bits to parallel bits format The operation of UART mostly control by one or
more register The process of read writes data to register are through input and output
ports Figure ld showing the address of a UART for COMI and COM4
The UART have FIFO or First in First out buffer FIFO bring the meaning as the first
data to enter the buffer are first to leave The function of buffer is to hold data temporary
before it was feed to the transmission medium The modem 16550A UART have16 bytes
FIFO This means 16 bytes can be writes to UART before anything was overwrite The
16550 UART was necessary for a high-speed communication under windows or
application running under window environment
Serial port Base Register Port Address
COM 1 3F8H COM2 2F8H COM3 3E8H COM3 2E8H
Figure ld The Serial Port Base Register Port [7 ]
23 Serial Communication
Serial communication is transmission of data over a serial interface one data bit at a time
In other word data are transfer through and forth over a single wire Therefore serial
communication is more cost effective than parallel communication RS232 is an example
for serial communication interface
24 Parallel Interface
Parallel communication is a way to sending more than one data at a time (normally eight
data bits) over to a parallel device or a Com Port For an example a computer will send
eight data bits of information to a parallel printer A very simple diagram of parallel
communication was present as Figure 2e The parallel interfaces require separated wire
8
------_------------__shyp
for sending separated data and therefor allowed faster and efficient data transmission On
the other hand to setting up a parallel communication network will be more costly than
serial communication network
1 Printer Interface
1 3 4 5 6 7 8
1 Computer Interface
2 3 4 5 6 7 8
Figure 2e A parallel Printer to Computer Interface [7 ]
25 Asynchronous and synchronous data
For two devices to communicate a way of synchronizing data must be set There are two
way ofdata formatting by using either asynchronous or synchronous
The synchronous operation is such a way that for each line data transmit it has a
separated clock to synchronous that data on a time of period For example data are
transfer once in each direction to and from the computer The synchronous data format
was show in figure 2f
While the asynchronous data is such a way that data are synchronous without clock
Each time the data are transmitting the receiver need to figure out how fast the data is
running The frame of asynchronous data has start and stops bit In another world the
frame always added with additional start and stop bit The asynchronous data format was
show in figure 2g
9
01100011100 o 1 1 1 11 0 0 0 0 001 0110 1 1 0
Unique Code
Continuous Block
Direction offlow
Figure 2f Synchronous data format I 8 ]
Start Stop d7 d6 d5 d4 d3 d2 dl dO Start
1 0 1 0 1 1 0 0I 1 I IMSB LSB
Start bit Stop bit1 Data-bits 1 I
r space mark mark space mark space mark mark space space
Serial Communication
Figure 2g Asynchronous Data Format Adopted form [8]
26 The Start Parity and Stop bits
For two machines to communicate to each other first thing both machines must agree on
the rate of speed for data transfer Second thing is the data must fonnatted for
synchronous or asynchronous operation Therefor for asynchronous operation the data
fonnatted in such a way that contains start and stop bit
271 Start bit
10
The TD line at interface device (Pin3) will go high when no data been transmit To start
transmit a data Transmit serial device will set TD line to low by means ofa start bit The
synchronous operation of DCE is waiting the TD line sign change from high bit to low
bit than DCE pauses half of a bit time and start sampling the incoming data until all the
character has been completely transmit To maintain synchronimtion DCE always
sampling the incoming data string at middle ofeach bit
272 Data bits
The data bits are the bits that contain character Nonnallyone character contains eight
bits Hence is the data bits showing character Amiddot 4tH
l start bit 41----shy Data bits j
shy
I t I Io 0 0 0 0 0
1 1deg1 1
Figure 2h The Data bits Format ( 7 ]
273 Parity bits
Four basic fonns ofparity bits are NONE EVEN ODD MARK and SPACE NONE use
for transmits a character without parity bit EVEN parity use to indicate by send logic 1
after a character if there is an odd number of logic 1 bit after a character data bit
Otherwise logic for EVEN parity goes to zero Odd parity will indicate by sending logic
1 after a data of a character bits if there is an even number of logic 1 after a characters
data bits Otherwise logic for ODD parity goes to zero Mark is logic 1 parity bit after a
data character and SPACE is logic zero after the data character
11
274 Stop bits
The stop bit indicated the end of a character The serial device was always send logic 1
for stop bit
28 Data Transmit and Receive Process
281 Transmit of a character
Several steps take before characters are transmitting from processor to modem
For an example communication between processor and 8251A USART
First the processor configures UART according to the communication protocol
Second an instruction was send to UART and set the flag TxEN Next The processor
was send the character to the data buffer ofUART Then this data buffer transfer the
character to transmit buffer for preparation for transmission Once data buffer was
complete transfer the character and ready to receive a new character the TXRDY flag
will set When processor automatically write in data buffer TXRDY flag automatically
reset
Next RTS (Ready to Send)pin output pin ofUART will alerted by modem that the bits
are about to transmit RTS pin for UART is tie together with modem RTS pin while the
modem realizes about to receive character from UART CTS pin will activated Then the
character was automatically transfer to modem The internal flag TxEMPTY will set
once the character was completely transmit from UART to modem
282 Receive of a character
The process of data receiving was also take several sequence First processor configures
UART according to standard protocol Then to receive a character the processor sends a
12
p
instruction to activated the RxE flag Next DART need to be alerted about the data going
to be transmitted DSR (Data Set Ready) will activated DSR pin of DART and modem
are tied together therefore when processor read this flags and realizes that the modem
has characters to be transmitted to DART Once DSR signal been set processor set DTR
(data terminal ready) to high And once DTR pin is asserted characters was
automatically transfer out from modem Once the characters is receive by DART it
formatted the data according to their start stop parity bits The RxRDY activated when a
character was completely receive
The bock diagram ofDART was show in ftgUre 2i
transmittedT~_B_r ~Mode Register
Transmit Register-~ I I data
I [_~~~J lt-~--r I
Receiver Register L~~~l-~~mmg =71 -_Rece~~I_v-e_r-B_-un_e=r=_-_ ~_romL--_
Devices and bullControl LogiC
l Internal Transmitter I Bus c-- ~ Clocking
--_______________rece_i_ve_r__lt=__-T Circuitary
Figure 2i USART Bloek Diagram [8 ]
28 COM Port setting
COM Port is the port that allowed computer to communicated with other device
such as modem or printer The standard personal computer normally has four
communications port COM 1 and COM 2 are assign for external port All the
13
TABLE OF CONTENTS
Contents Pages
iiDEDICATION
ACKNOWLEDGEMENT iii
ABSTRAK iv
ABSTRACT v
TABLE OF CONTENTS vi
LIST OF ILLUSTRATION ix
Chapter 1 Wireless Communication An Overview
10 An Introduction 1 11 Wireless Network 1 12 Fundamental ofa Wireless Internet System 2 13 The Purpose of This Paper 2
CbapterZ RSZ3Z Interface amp Serial Communication
20 Overview 5 21 RS232 Pin Abbreviation 6 22 DART 7 23 Serial Communication 8 24 Parallel Communication 8 25 Asynchronous amp Synchronous Data 9 26 The Start Data Parity and Stop bit 10
261 Start bit 11 262 Data bits 11 263 Parity bits 11 264 Stop bit 12
27 Data Transmit amp Receive Process 12 281 Transmit ofa character 12 282 Receive ofa character 13
28 COM Port Setting 14
VI
Chapter 3 Laser as a Communication Medium
30 Fundamental of light 15 31 What is Laser 17 32 Characteristic ofa Laser Beam 19 33 Type ofLaser 20
331 Semiconductor Laser 20 332 Gas Lasers 20 333 Solid State Laser Nd YAG Laser 21
34 Light Modulation Scheme 22 35 Several Optical Modulation Techniques 25
351 Analog modulation 25 352 Pulse Modulation Technique 27
Chapter 4 Modulation Technique for Wireless System
40 Why Need Modulation 29 41 Amplitude Modulation 29 42 Frequency Modulation-AMPS 30 43 Generation ofFrequency Modula 31 44 Digital Modulation Technique 32 45 Frequency Shift Keying 32 46 Phase Shift Keying 35 47 Quadrature Phase Shift Keying 36 48 Offset Quadrature Phase Shift Keying 37 49 Minimum Shift Keying 39
Chapter 5 Laser Safety
50 Laser Beam Hazard 41 51 Safety Precaution amp Control Procedure 41 52 Class ofLaser 42
Chapter 6 System Design
60 Basic Overview 43 61 System Design 44 62 The Block Diagram 44 63 Function For Each Block 45 64 The Construction 45 65 Construction PCB 47 66 Observation 47 67 Testing
VII
p
Chapter 7 Software Analysis
70 Software Overview 50 71 Include Header File 53 72 Define The Setting 54 73 The Other Function 54 74 The Other Testing Program 55
ChapterS Conclusion
80 The Conclusion 58 81 The Future Work 58
APPENDIX A 60
REFERENCE 61
vm
LIST OF ILLUSTRATION
Figure Page
18 THE BLOCK DIAGRAM OF TYPICAL NETWORK 2
Ib CELCOMtrade DATA2GONETWORK
Ie SIMPLEST POINT-TO-POINT DATA COMMUNICATION VIA
2
RS232 LASER TRANSCEIVER 4
28 THE RS232 PIN CONFIGURATION 6
2b A NULL MODEM CONFIGURATION 6
2e DETAIL EXPLANATION OF RS232 PIN ABBREVIATION 7
2d THE SERIAL PORT BASE REGISTER 8
2e A PARALLEL PRINTER TO COMPUTER CONFIGURATION 9
2f SYNCHRONOUS DATA FORMAT 10
2g ASYNCBRONOUS DATA FORMAT 10
2h THE DATA BIT FORMAT 11
2i USART BLOCK DIAGRAM 13
3a ELECTRIC AND MAGNETIC FIELD IN PLANE ELECTROMAGNETIC WAVE 16
3b ILLUSTRATION OF ENERGY DIAGRAM FOR TWO LEVEL ENERGY SYSTEM ABSORPTION STIMULATED EMISSION 19 SPONTANEOUS EMISSION
3e SPATIAL COHERENT AT FOCUSING POINT 20
IX
po
3d EXCITATION OF GASEOUS LASER MEDIUM REFLECTION 21 OF PHOTON DURING STIMULATED EMISSION EXITING PHOTON IN LASER BEAM
SIGNAL (C) INTENSITY OF LIGHT
3e SCHEMATIC DIAGRAM FOR AN END PUMPED ND YAGLASER 22
3f THE ELECTROMAGNETIC SPECTRUM 23
3g AMPLITUDE MODULATION OF OPTICAL LIGHT BEAM 24
3h NON RETURN ZERO FORMAT 24
3i RETURN TO ZERO FORMAT 24
3j USING FM MODULATION TO MODULATED INTENSITY OF tiGHT (A) MASSAGE AMPUTUDE (B) FM MODULATION 25
4a AM SIGNAL MODULATION 30
4b FM SIGNAL MODULATION 31
4c FREQUENCY MODULATION 32
4d FSKFORMAT 33
4e FORMATION OF FSK SIGNAL 34
4f NON COHERENT DEMODULATION 35
4g COHERENT DEMODULATION 35
4h PSK WAVEFORM 36
4i THE GENERATION OF QPSK SIGNAL 37
4j OQPSK WAVEFORM (HALF SYMBOL OFFSET) 38
4k GENERATION ON OQPSK SIGNAL 39
41 GENERATION OF MSK WAVEFORM 40
4m OUTPUT WAVEFORM OF MSK SIGNAL 41
x
5a LASER WARNING LABEL 42
6a SIMPLE BLOCK DIAGRAM RS131 LASER COMMUNICATION SYSTEM 43
6b BLOCK DIAGRAM OF RS131 LASER TRANSCEIVER 44
6c SCHEMATIC OF TRANSCEIVER 45
6d PCB LAYOUT 46
6e DB9JUMPERING 48
7a THE HEADER FILE 54
7b THESETI1NG 55
7c BIOSCOM EXAMPLE 56
7d BIOS_SERIALCOM EXAMPLE 57
XI
CHAPTERt
WIRELESS COMMUNICATION AN OVERVIEW
to An Introduction
A communication occurs when there was an infonnation flow The word
telecommunication is derive from the Greek tele far of and communicare to share
[1] The communication is the process of transferring interpreting and processing
infonnation (data) among the people machines and place This process implies that we
need a sender a medium and a receiver to perform infonnation flow Therefore the
telecommunication is the process of exchanging the data of information in any useable
fonn in any natural delivery among two or more user by using radio wire and light and
other mechanical means
1t Wireless Network
Consider a cellular telephone system that provided coverage in a geographical
area as figure ta shown
To provide wireless communication within a region a Radio Base Station (RBS) must be
set up The Radio Base Station will perfonn the function as access point to the mobile
user and a connection with Mobile Switching Center A mobile user connected to base
station through Common Air Interface which can also called Handshaking ProtocoL [2]
The Radio Base Station will connect to mobile Switching Center through landline The
mobile switching center will provide connectivity to Public Switch Telephone Network
The PSTN Switching Center will provide connectivity to global network
The basic concept of a wireless network was to establishing the mobile user to a base
station followed by connection with mobile switch center and from mobile center
connected to global network
1
Mobile SWltchlna Center(MSC) or
Mobile Telephone SWItohlna omce Voice and Data link
(Landline or ~microwave)
Q ~ ~P-
PSTN
regRadio Link air interface
Figure la The Block Diagram of a Typical Wireless Network [ 2 ]
PSTN network and mobile network will connect by either fix-line or radio wave For the
fixmiddotline It will be twisted copper cable coaxial cable fiber optics cable For the radio
wave it either use microwave and satellite link The characteristic of a PSTN network is
the user was fix at one location while the mobile network allowed the user to move
within the coverage area The process of moving within the coverage area called
Roaming
12 Fundamental of a Wireless Intemet System
To accessing the internet a cellular user need to use a PCMCIA card with the adapter to
connected to laptop in the area where PSTN line was not accessible For example the
product of Celcom Data2Go for wireless data communication can have the following
function shy
e Electronic mail system
e Sending and receiving fax
2
bull Accessing Company database
bull Submit customer order
bull On-line information service
bull accessing Internet-surfing into Netscape
bull terminal mode- billinwregistration
The network ofData2Go by Celcomtradeas shown shy
Figure Ib Celcomtrade Data2Go Network 14 I
Software uses for this type ofnetwork are
bull Delrina WinFaxPro
bull Microsoft Mail
bull Netscape
bull Lotus Notes
13 The purpose of this paper
The main purpose of this project is to develop a useable technique that suitable for
sending data wireless via RS232 communication port The system component will consist
of a desktop computer that act as input device a standard RS232 interface a transceiver
for transmit and receive signal and a modify laser poniter The suggested system will be
3
set and tested in a point-to-point configuration As the figure show below the network
diagram stated shy
J -~HJj----tcooo ~ IEco~codl---=RS=232=--_~ Personal computer Signal RS232 Laser Transceiver RS2321aser Transceiver Personal computer
Figure lc The Simples point to point data communication via RS131laser transceiver
4
Cbapter2
RS-232 INTERFACE AND SERIAL COMMUNICATION
20 Overview
RS 232 Interface in a simple universal well knows data interface RS means
Recommended Standard1 The female connector attaches to Data Communication
Equipment and male connector attaches to Data Terminal Equipment Mostly today PCs
are equipped with two RS232 ports via COMI or COM2 The additional COM port
COM3 and COM4 required additional card
RS-232 defines 25-pin communication line Every line has their own function to
accessing data The configurations ofevery pin layout are show in figure 2a
Normally The ground signal refers to pin 7 Two computers can communicate by using a
null modem A null modem is a special made direct cable and connector It is functioning
like a modem but has limited transmission range Figure 2b illustrated the common
method to wiring a null modem Pin2 and pin3 are wire together and all the cables are
connect in such a way a modem simulated between two computers
The electrical characteristic define by RS232 as
(a) Total capacitance not less than 2500 pF
(b) (b) A binary high logic output lines is + 5to + 15 volts input lines is from +3
to + 15 volts
(c) A binary low logic output lines is from -5 to -15 volts input lines is from -3
to -15 volts
(d) output lines voltages -5 and +5 -3 and +3 volts for input lines are undefined
5
Shelld~ Secondary
tntnsmltted data Transmlttins
Signal element timlne (DCEoTE)
Secondary
Relcetver received data
Signal tlmlne(DCEoTE) Looak
Loopok Secondary
Request To8end
DTERudy
Rem_ Loopb8ok amp Signal Qua
Decmlctor RinS indicator
l reg
Transmitted Data
Request to Send
DCEReady
Rivedline 818nal Detector
Reserved (Testing)
Secondary Received Lne Signel Detector
Recetve Data
reg
Crto8ent
Signal Ground Comman RetUrn
reg Rrved (Testing)
Datas18nal
I 10
rate ct UnusedTnulSmitter signal Signed
element -f
timing (DTE-DCE) bull Tnt Mode 8eooundary~ 13 c
To8ent~
Figure 2a The RS232 pin configuration [81
Pin Number Line Line Pin Number
2 m m 2
3 RD RD 3
4 RTS RTS 4
5 CTS CTS 5
6 DSR---- DSR 6
7 Common 7
8 DCD DCD 8
20 DTR DTR 20
22 R1 R1 22
Figure 2b A Null Modem Configuration [8]
6
21 The Explanation For RS1Jl Pin Abbreviation
Hence is the detail ofeach line in DB9 and DB25 function
Clear to Send (CTS)
Data Carrier Detect (OCR)
Data Set Ready (DSR)
Data Terminal Ready (DTR)
Receive Data (RO)
Ring Indicator (RI)
Requested to Send (RTS)
Transmit Data (TD)
asserted (logic state 1) by DCE it is ready to receive data
logic state 1 whenever there is data link in progress
logic state 1 when DCE is ready to communicated withDTE
logic state 1 when DTE is ready to communicated withDCE
use by DCE to send data to DTE
logic 1 by DCE when a ring is detect
logic state 1 by DTE when it want to transmit data toDCE
Use by DTE to send data to DCE
Figure lc The Detail Explanation of Abbreviation [ 8]
22 UART
UART Universal Asynchronous Receiver Transmitter is a special hardware in RS232
serial interface It sometime called as Asynchronous Communication Element
Most of the new personal computer today is equip with 16450 and 16550 UART The
function ofUART chip is to convert the parallel data to a serial data format that enable a
serial communication between two computers The UART chip also uses to convert back
7
the serial bits to parallel bits format The operation of UART mostly control by one or
more register The process of read writes data to register are through input and output
ports Figure ld showing the address of a UART for COMI and COM4
The UART have FIFO or First in First out buffer FIFO bring the meaning as the first
data to enter the buffer are first to leave The function of buffer is to hold data temporary
before it was feed to the transmission medium The modem 16550A UART have16 bytes
FIFO This means 16 bytes can be writes to UART before anything was overwrite The
16550 UART was necessary for a high-speed communication under windows or
application running under window environment
Serial port Base Register Port Address
COM 1 3F8H COM2 2F8H COM3 3E8H COM3 2E8H
Figure ld The Serial Port Base Register Port [7 ]
23 Serial Communication
Serial communication is transmission of data over a serial interface one data bit at a time
In other word data are transfer through and forth over a single wire Therefore serial
communication is more cost effective than parallel communication RS232 is an example
for serial communication interface
24 Parallel Interface
Parallel communication is a way to sending more than one data at a time (normally eight
data bits) over to a parallel device or a Com Port For an example a computer will send
eight data bits of information to a parallel printer A very simple diagram of parallel
communication was present as Figure 2e The parallel interfaces require separated wire
8
------_------------__shyp
for sending separated data and therefor allowed faster and efficient data transmission On
the other hand to setting up a parallel communication network will be more costly than
serial communication network
1 Printer Interface
1 3 4 5 6 7 8
1 Computer Interface
2 3 4 5 6 7 8
Figure 2e A parallel Printer to Computer Interface [7 ]
25 Asynchronous and synchronous data
For two devices to communicate a way of synchronizing data must be set There are two
way ofdata formatting by using either asynchronous or synchronous
The synchronous operation is such a way that for each line data transmit it has a
separated clock to synchronous that data on a time of period For example data are
transfer once in each direction to and from the computer The synchronous data format
was show in figure 2f
While the asynchronous data is such a way that data are synchronous without clock
Each time the data are transmitting the receiver need to figure out how fast the data is
running The frame of asynchronous data has start and stops bit In another world the
frame always added with additional start and stop bit The asynchronous data format was
show in figure 2g
9
01100011100 o 1 1 1 11 0 0 0 0 001 0110 1 1 0
Unique Code
Continuous Block
Direction offlow
Figure 2f Synchronous data format I 8 ]
Start Stop d7 d6 d5 d4 d3 d2 dl dO Start
1 0 1 0 1 1 0 0I 1 I IMSB LSB
Start bit Stop bit1 Data-bits 1 I
r space mark mark space mark space mark mark space space
Serial Communication
Figure 2g Asynchronous Data Format Adopted form [8]
26 The Start Parity and Stop bits
For two machines to communicate to each other first thing both machines must agree on
the rate of speed for data transfer Second thing is the data must fonnatted for
synchronous or asynchronous operation Therefor for asynchronous operation the data
fonnatted in such a way that contains start and stop bit
271 Start bit
10
The TD line at interface device (Pin3) will go high when no data been transmit To start
transmit a data Transmit serial device will set TD line to low by means ofa start bit The
synchronous operation of DCE is waiting the TD line sign change from high bit to low
bit than DCE pauses half of a bit time and start sampling the incoming data until all the
character has been completely transmit To maintain synchronimtion DCE always
sampling the incoming data string at middle ofeach bit
272 Data bits
The data bits are the bits that contain character Nonnallyone character contains eight
bits Hence is the data bits showing character Amiddot 4tH
l start bit 41----shy Data bits j
shy
I t I Io 0 0 0 0 0
1 1deg1 1
Figure 2h The Data bits Format ( 7 ]
273 Parity bits
Four basic fonns ofparity bits are NONE EVEN ODD MARK and SPACE NONE use
for transmits a character without parity bit EVEN parity use to indicate by send logic 1
after a character if there is an odd number of logic 1 bit after a character data bit
Otherwise logic for EVEN parity goes to zero Odd parity will indicate by sending logic
1 after a data of a character bits if there is an even number of logic 1 after a characters
data bits Otherwise logic for ODD parity goes to zero Mark is logic 1 parity bit after a
data character and SPACE is logic zero after the data character
11
274 Stop bits
The stop bit indicated the end of a character The serial device was always send logic 1
for stop bit
28 Data Transmit and Receive Process
281 Transmit of a character
Several steps take before characters are transmitting from processor to modem
For an example communication between processor and 8251A USART
First the processor configures UART according to the communication protocol
Second an instruction was send to UART and set the flag TxEN Next The processor
was send the character to the data buffer ofUART Then this data buffer transfer the
character to transmit buffer for preparation for transmission Once data buffer was
complete transfer the character and ready to receive a new character the TXRDY flag
will set When processor automatically write in data buffer TXRDY flag automatically
reset
Next RTS (Ready to Send)pin output pin ofUART will alerted by modem that the bits
are about to transmit RTS pin for UART is tie together with modem RTS pin while the
modem realizes about to receive character from UART CTS pin will activated Then the
character was automatically transfer to modem The internal flag TxEMPTY will set
once the character was completely transmit from UART to modem
282 Receive of a character
The process of data receiving was also take several sequence First processor configures
UART according to standard protocol Then to receive a character the processor sends a
12
p
instruction to activated the RxE flag Next DART need to be alerted about the data going
to be transmitted DSR (Data Set Ready) will activated DSR pin of DART and modem
are tied together therefore when processor read this flags and realizes that the modem
has characters to be transmitted to DART Once DSR signal been set processor set DTR
(data terminal ready) to high And once DTR pin is asserted characters was
automatically transfer out from modem Once the characters is receive by DART it
formatted the data according to their start stop parity bits The RxRDY activated when a
character was completely receive
The bock diagram ofDART was show in ftgUre 2i
transmittedT~_B_r ~Mode Register
Transmit Register-~ I I data
I [_~~~J lt-~--r I
Receiver Register L~~~l-~~mmg =71 -_Rece~~I_v-e_r-B_-un_e=r=_-_ ~_romL--_
Devices and bullControl LogiC
l Internal Transmitter I Bus c-- ~ Clocking
--_______________rece_i_ve_r__lt=__-T Circuitary
Figure 2i USART Bloek Diagram [8 ]
28 COM Port setting
COM Port is the port that allowed computer to communicated with other device
such as modem or printer The standard personal computer normally has four
communications port COM 1 and COM 2 are assign for external port All the
13
Chapter 3 Laser as a Communication Medium
30 Fundamental of light 15 31 What is Laser 17 32 Characteristic ofa Laser Beam 19 33 Type ofLaser 20
331 Semiconductor Laser 20 332 Gas Lasers 20 333 Solid State Laser Nd YAG Laser 21
34 Light Modulation Scheme 22 35 Several Optical Modulation Techniques 25
351 Analog modulation 25 352 Pulse Modulation Technique 27
Chapter 4 Modulation Technique for Wireless System
40 Why Need Modulation 29 41 Amplitude Modulation 29 42 Frequency Modulation-AMPS 30 43 Generation ofFrequency Modula 31 44 Digital Modulation Technique 32 45 Frequency Shift Keying 32 46 Phase Shift Keying 35 47 Quadrature Phase Shift Keying 36 48 Offset Quadrature Phase Shift Keying 37 49 Minimum Shift Keying 39
Chapter 5 Laser Safety
50 Laser Beam Hazard 41 51 Safety Precaution amp Control Procedure 41 52 Class ofLaser 42
Chapter 6 System Design
60 Basic Overview 43 61 System Design 44 62 The Block Diagram 44 63 Function For Each Block 45 64 The Construction 45 65 Construction PCB 47 66 Observation 47 67 Testing
VII
p
Chapter 7 Software Analysis
70 Software Overview 50 71 Include Header File 53 72 Define The Setting 54 73 The Other Function 54 74 The Other Testing Program 55
ChapterS Conclusion
80 The Conclusion 58 81 The Future Work 58
APPENDIX A 60
REFERENCE 61
vm
LIST OF ILLUSTRATION
Figure Page
18 THE BLOCK DIAGRAM OF TYPICAL NETWORK 2
Ib CELCOMtrade DATA2GONETWORK
Ie SIMPLEST POINT-TO-POINT DATA COMMUNICATION VIA
2
RS232 LASER TRANSCEIVER 4
28 THE RS232 PIN CONFIGURATION 6
2b A NULL MODEM CONFIGURATION 6
2e DETAIL EXPLANATION OF RS232 PIN ABBREVIATION 7
2d THE SERIAL PORT BASE REGISTER 8
2e A PARALLEL PRINTER TO COMPUTER CONFIGURATION 9
2f SYNCHRONOUS DATA FORMAT 10
2g ASYNCBRONOUS DATA FORMAT 10
2h THE DATA BIT FORMAT 11
2i USART BLOCK DIAGRAM 13
3a ELECTRIC AND MAGNETIC FIELD IN PLANE ELECTROMAGNETIC WAVE 16
3b ILLUSTRATION OF ENERGY DIAGRAM FOR TWO LEVEL ENERGY SYSTEM ABSORPTION STIMULATED EMISSION 19 SPONTANEOUS EMISSION
3e SPATIAL COHERENT AT FOCUSING POINT 20
IX
po
3d EXCITATION OF GASEOUS LASER MEDIUM REFLECTION 21 OF PHOTON DURING STIMULATED EMISSION EXITING PHOTON IN LASER BEAM
SIGNAL (C) INTENSITY OF LIGHT
3e SCHEMATIC DIAGRAM FOR AN END PUMPED ND YAGLASER 22
3f THE ELECTROMAGNETIC SPECTRUM 23
3g AMPLITUDE MODULATION OF OPTICAL LIGHT BEAM 24
3h NON RETURN ZERO FORMAT 24
3i RETURN TO ZERO FORMAT 24
3j USING FM MODULATION TO MODULATED INTENSITY OF tiGHT (A) MASSAGE AMPUTUDE (B) FM MODULATION 25
4a AM SIGNAL MODULATION 30
4b FM SIGNAL MODULATION 31
4c FREQUENCY MODULATION 32
4d FSKFORMAT 33
4e FORMATION OF FSK SIGNAL 34
4f NON COHERENT DEMODULATION 35
4g COHERENT DEMODULATION 35
4h PSK WAVEFORM 36
4i THE GENERATION OF QPSK SIGNAL 37
4j OQPSK WAVEFORM (HALF SYMBOL OFFSET) 38
4k GENERATION ON OQPSK SIGNAL 39
41 GENERATION OF MSK WAVEFORM 40
4m OUTPUT WAVEFORM OF MSK SIGNAL 41
x
5a LASER WARNING LABEL 42
6a SIMPLE BLOCK DIAGRAM RS131 LASER COMMUNICATION SYSTEM 43
6b BLOCK DIAGRAM OF RS131 LASER TRANSCEIVER 44
6c SCHEMATIC OF TRANSCEIVER 45
6d PCB LAYOUT 46
6e DB9JUMPERING 48
7a THE HEADER FILE 54
7b THESETI1NG 55
7c BIOSCOM EXAMPLE 56
7d BIOS_SERIALCOM EXAMPLE 57
XI
CHAPTERt
WIRELESS COMMUNICATION AN OVERVIEW
to An Introduction
A communication occurs when there was an infonnation flow The word
telecommunication is derive from the Greek tele far of and communicare to share
[1] The communication is the process of transferring interpreting and processing
infonnation (data) among the people machines and place This process implies that we
need a sender a medium and a receiver to perform infonnation flow Therefore the
telecommunication is the process of exchanging the data of information in any useable
fonn in any natural delivery among two or more user by using radio wire and light and
other mechanical means
1t Wireless Network
Consider a cellular telephone system that provided coverage in a geographical
area as figure ta shown
To provide wireless communication within a region a Radio Base Station (RBS) must be
set up The Radio Base Station will perfonn the function as access point to the mobile
user and a connection with Mobile Switching Center A mobile user connected to base
station through Common Air Interface which can also called Handshaking ProtocoL [2]
The Radio Base Station will connect to mobile Switching Center through landline The
mobile switching center will provide connectivity to Public Switch Telephone Network
The PSTN Switching Center will provide connectivity to global network
The basic concept of a wireless network was to establishing the mobile user to a base
station followed by connection with mobile switch center and from mobile center
connected to global network
1
Mobile SWltchlna Center(MSC) or
Mobile Telephone SWItohlna omce Voice and Data link
(Landline or ~microwave)
Q ~ ~P-
PSTN
regRadio Link air interface
Figure la The Block Diagram of a Typical Wireless Network [ 2 ]
PSTN network and mobile network will connect by either fix-line or radio wave For the
fixmiddotline It will be twisted copper cable coaxial cable fiber optics cable For the radio
wave it either use microwave and satellite link The characteristic of a PSTN network is
the user was fix at one location while the mobile network allowed the user to move
within the coverage area The process of moving within the coverage area called
Roaming
12 Fundamental of a Wireless Intemet System
To accessing the internet a cellular user need to use a PCMCIA card with the adapter to
connected to laptop in the area where PSTN line was not accessible For example the
product of Celcom Data2Go for wireless data communication can have the following
function shy
e Electronic mail system
e Sending and receiving fax
2
bull Accessing Company database
bull Submit customer order
bull On-line information service
bull accessing Internet-surfing into Netscape
bull terminal mode- billinwregistration
The network ofData2Go by Celcomtradeas shown shy
Figure Ib Celcomtrade Data2Go Network 14 I
Software uses for this type ofnetwork are
bull Delrina WinFaxPro
bull Microsoft Mail
bull Netscape
bull Lotus Notes
13 The purpose of this paper
The main purpose of this project is to develop a useable technique that suitable for
sending data wireless via RS232 communication port The system component will consist
of a desktop computer that act as input device a standard RS232 interface a transceiver
for transmit and receive signal and a modify laser poniter The suggested system will be
3
set and tested in a point-to-point configuration As the figure show below the network
diagram stated shy
J -~HJj----tcooo ~ IEco~codl---=RS=232=--_~ Personal computer Signal RS232 Laser Transceiver RS2321aser Transceiver Personal computer
Figure lc The Simples point to point data communication via RS131laser transceiver
4
Cbapter2
RS-232 INTERFACE AND SERIAL COMMUNICATION
20 Overview
RS 232 Interface in a simple universal well knows data interface RS means
Recommended Standard1 The female connector attaches to Data Communication
Equipment and male connector attaches to Data Terminal Equipment Mostly today PCs
are equipped with two RS232 ports via COMI or COM2 The additional COM port
COM3 and COM4 required additional card
RS-232 defines 25-pin communication line Every line has their own function to
accessing data The configurations ofevery pin layout are show in figure 2a
Normally The ground signal refers to pin 7 Two computers can communicate by using a
null modem A null modem is a special made direct cable and connector It is functioning
like a modem but has limited transmission range Figure 2b illustrated the common
method to wiring a null modem Pin2 and pin3 are wire together and all the cables are
connect in such a way a modem simulated between two computers
The electrical characteristic define by RS232 as
(a) Total capacitance not less than 2500 pF
(b) (b) A binary high logic output lines is + 5to + 15 volts input lines is from +3
to + 15 volts
(c) A binary low logic output lines is from -5 to -15 volts input lines is from -3
to -15 volts
(d) output lines voltages -5 and +5 -3 and +3 volts for input lines are undefined
5
Shelld~ Secondary
tntnsmltted data Transmlttins
Signal element timlne (DCEoTE)
Secondary
Relcetver received data
Signal tlmlne(DCEoTE) Looak
Loopok Secondary
Request To8end
DTERudy
Rem_ Loopb8ok amp Signal Qua
Decmlctor RinS indicator
l reg
Transmitted Data
Request to Send
DCEReady
Rivedline 818nal Detector
Reserved (Testing)
Secondary Received Lne Signel Detector
Recetve Data
reg
Crto8ent
Signal Ground Comman RetUrn
reg Rrved (Testing)
Datas18nal
I 10
rate ct UnusedTnulSmitter signal Signed
element -f
timing (DTE-DCE) bull Tnt Mode 8eooundary~ 13 c
To8ent~
Figure 2a The RS232 pin configuration [81
Pin Number Line Line Pin Number
2 m m 2
3 RD RD 3
4 RTS RTS 4
5 CTS CTS 5
6 DSR---- DSR 6
7 Common 7
8 DCD DCD 8
20 DTR DTR 20
22 R1 R1 22
Figure 2b A Null Modem Configuration [8]
6
21 The Explanation For RS1Jl Pin Abbreviation
Hence is the detail ofeach line in DB9 and DB25 function
Clear to Send (CTS)
Data Carrier Detect (OCR)
Data Set Ready (DSR)
Data Terminal Ready (DTR)
Receive Data (RO)
Ring Indicator (RI)
Requested to Send (RTS)
Transmit Data (TD)
asserted (logic state 1) by DCE it is ready to receive data
logic state 1 whenever there is data link in progress
logic state 1 when DCE is ready to communicated withDTE
logic state 1 when DTE is ready to communicated withDCE
use by DCE to send data to DTE
logic 1 by DCE when a ring is detect
logic state 1 by DTE when it want to transmit data toDCE
Use by DTE to send data to DCE
Figure lc The Detail Explanation of Abbreviation [ 8]
22 UART
UART Universal Asynchronous Receiver Transmitter is a special hardware in RS232
serial interface It sometime called as Asynchronous Communication Element
Most of the new personal computer today is equip with 16450 and 16550 UART The
function ofUART chip is to convert the parallel data to a serial data format that enable a
serial communication between two computers The UART chip also uses to convert back
7
the serial bits to parallel bits format The operation of UART mostly control by one or
more register The process of read writes data to register are through input and output
ports Figure ld showing the address of a UART for COMI and COM4
The UART have FIFO or First in First out buffer FIFO bring the meaning as the first
data to enter the buffer are first to leave The function of buffer is to hold data temporary
before it was feed to the transmission medium The modem 16550A UART have16 bytes
FIFO This means 16 bytes can be writes to UART before anything was overwrite The
16550 UART was necessary for a high-speed communication under windows or
application running under window environment
Serial port Base Register Port Address
COM 1 3F8H COM2 2F8H COM3 3E8H COM3 2E8H
Figure ld The Serial Port Base Register Port [7 ]
23 Serial Communication
Serial communication is transmission of data over a serial interface one data bit at a time
In other word data are transfer through and forth over a single wire Therefore serial
communication is more cost effective than parallel communication RS232 is an example
for serial communication interface
24 Parallel Interface
Parallel communication is a way to sending more than one data at a time (normally eight
data bits) over to a parallel device or a Com Port For an example a computer will send
eight data bits of information to a parallel printer A very simple diagram of parallel
communication was present as Figure 2e The parallel interfaces require separated wire
8
------_------------__shyp
for sending separated data and therefor allowed faster and efficient data transmission On
the other hand to setting up a parallel communication network will be more costly than
serial communication network
1 Printer Interface
1 3 4 5 6 7 8
1 Computer Interface
2 3 4 5 6 7 8
Figure 2e A parallel Printer to Computer Interface [7 ]
25 Asynchronous and synchronous data
For two devices to communicate a way of synchronizing data must be set There are two
way ofdata formatting by using either asynchronous or synchronous
The synchronous operation is such a way that for each line data transmit it has a
separated clock to synchronous that data on a time of period For example data are
transfer once in each direction to and from the computer The synchronous data format
was show in figure 2f
While the asynchronous data is such a way that data are synchronous without clock
Each time the data are transmitting the receiver need to figure out how fast the data is
running The frame of asynchronous data has start and stops bit In another world the
frame always added with additional start and stop bit The asynchronous data format was
show in figure 2g
9
01100011100 o 1 1 1 11 0 0 0 0 001 0110 1 1 0
Unique Code
Continuous Block
Direction offlow
Figure 2f Synchronous data format I 8 ]
Start Stop d7 d6 d5 d4 d3 d2 dl dO Start
1 0 1 0 1 1 0 0I 1 I IMSB LSB
Start bit Stop bit1 Data-bits 1 I
r space mark mark space mark space mark mark space space
Serial Communication
Figure 2g Asynchronous Data Format Adopted form [8]
26 The Start Parity and Stop bits
For two machines to communicate to each other first thing both machines must agree on
the rate of speed for data transfer Second thing is the data must fonnatted for
synchronous or asynchronous operation Therefor for asynchronous operation the data
fonnatted in such a way that contains start and stop bit
271 Start bit
10
The TD line at interface device (Pin3) will go high when no data been transmit To start
transmit a data Transmit serial device will set TD line to low by means ofa start bit The
synchronous operation of DCE is waiting the TD line sign change from high bit to low
bit than DCE pauses half of a bit time and start sampling the incoming data until all the
character has been completely transmit To maintain synchronimtion DCE always
sampling the incoming data string at middle ofeach bit
272 Data bits
The data bits are the bits that contain character Nonnallyone character contains eight
bits Hence is the data bits showing character Amiddot 4tH
l start bit 41----shy Data bits j
shy
I t I Io 0 0 0 0 0
1 1deg1 1
Figure 2h The Data bits Format ( 7 ]
273 Parity bits
Four basic fonns ofparity bits are NONE EVEN ODD MARK and SPACE NONE use
for transmits a character without parity bit EVEN parity use to indicate by send logic 1
after a character if there is an odd number of logic 1 bit after a character data bit
Otherwise logic for EVEN parity goes to zero Odd parity will indicate by sending logic
1 after a data of a character bits if there is an even number of logic 1 after a characters
data bits Otherwise logic for ODD parity goes to zero Mark is logic 1 parity bit after a
data character and SPACE is logic zero after the data character
11
274 Stop bits
The stop bit indicated the end of a character The serial device was always send logic 1
for stop bit
28 Data Transmit and Receive Process
281 Transmit of a character
Several steps take before characters are transmitting from processor to modem
For an example communication between processor and 8251A USART
First the processor configures UART according to the communication protocol
Second an instruction was send to UART and set the flag TxEN Next The processor
was send the character to the data buffer ofUART Then this data buffer transfer the
character to transmit buffer for preparation for transmission Once data buffer was
complete transfer the character and ready to receive a new character the TXRDY flag
will set When processor automatically write in data buffer TXRDY flag automatically
reset
Next RTS (Ready to Send)pin output pin ofUART will alerted by modem that the bits
are about to transmit RTS pin for UART is tie together with modem RTS pin while the
modem realizes about to receive character from UART CTS pin will activated Then the
character was automatically transfer to modem The internal flag TxEMPTY will set
once the character was completely transmit from UART to modem
282 Receive of a character
The process of data receiving was also take several sequence First processor configures
UART according to standard protocol Then to receive a character the processor sends a
12
p
instruction to activated the RxE flag Next DART need to be alerted about the data going
to be transmitted DSR (Data Set Ready) will activated DSR pin of DART and modem
are tied together therefore when processor read this flags and realizes that the modem
has characters to be transmitted to DART Once DSR signal been set processor set DTR
(data terminal ready) to high And once DTR pin is asserted characters was
automatically transfer out from modem Once the characters is receive by DART it
formatted the data according to their start stop parity bits The RxRDY activated when a
character was completely receive
The bock diagram ofDART was show in ftgUre 2i
transmittedT~_B_r ~Mode Register
Transmit Register-~ I I data
I [_~~~J lt-~--r I
Receiver Register L~~~l-~~mmg =71 -_Rece~~I_v-e_r-B_-un_e=r=_-_ ~_romL--_
Devices and bullControl LogiC
l Internal Transmitter I Bus c-- ~ Clocking
--_______________rece_i_ve_r__lt=__-T Circuitary
Figure 2i USART Bloek Diagram [8 ]
28 COM Port setting
COM Port is the port that allowed computer to communicated with other device
such as modem or printer The standard personal computer normally has four
communications port COM 1 and COM 2 are assign for external port All the
13
p
Chapter 7 Software Analysis
70 Software Overview 50 71 Include Header File 53 72 Define The Setting 54 73 The Other Function 54 74 The Other Testing Program 55
ChapterS Conclusion
80 The Conclusion 58 81 The Future Work 58
APPENDIX A 60
REFERENCE 61
vm
LIST OF ILLUSTRATION
Figure Page
18 THE BLOCK DIAGRAM OF TYPICAL NETWORK 2
Ib CELCOMtrade DATA2GONETWORK
Ie SIMPLEST POINT-TO-POINT DATA COMMUNICATION VIA
2
RS232 LASER TRANSCEIVER 4
28 THE RS232 PIN CONFIGURATION 6
2b A NULL MODEM CONFIGURATION 6
2e DETAIL EXPLANATION OF RS232 PIN ABBREVIATION 7
2d THE SERIAL PORT BASE REGISTER 8
2e A PARALLEL PRINTER TO COMPUTER CONFIGURATION 9
2f SYNCHRONOUS DATA FORMAT 10
2g ASYNCBRONOUS DATA FORMAT 10
2h THE DATA BIT FORMAT 11
2i USART BLOCK DIAGRAM 13
3a ELECTRIC AND MAGNETIC FIELD IN PLANE ELECTROMAGNETIC WAVE 16
3b ILLUSTRATION OF ENERGY DIAGRAM FOR TWO LEVEL ENERGY SYSTEM ABSORPTION STIMULATED EMISSION 19 SPONTANEOUS EMISSION
3e SPATIAL COHERENT AT FOCUSING POINT 20
IX
po
3d EXCITATION OF GASEOUS LASER MEDIUM REFLECTION 21 OF PHOTON DURING STIMULATED EMISSION EXITING PHOTON IN LASER BEAM
SIGNAL (C) INTENSITY OF LIGHT
3e SCHEMATIC DIAGRAM FOR AN END PUMPED ND YAGLASER 22
3f THE ELECTROMAGNETIC SPECTRUM 23
3g AMPLITUDE MODULATION OF OPTICAL LIGHT BEAM 24
3h NON RETURN ZERO FORMAT 24
3i RETURN TO ZERO FORMAT 24
3j USING FM MODULATION TO MODULATED INTENSITY OF tiGHT (A) MASSAGE AMPUTUDE (B) FM MODULATION 25
4a AM SIGNAL MODULATION 30
4b FM SIGNAL MODULATION 31
4c FREQUENCY MODULATION 32
4d FSKFORMAT 33
4e FORMATION OF FSK SIGNAL 34
4f NON COHERENT DEMODULATION 35
4g COHERENT DEMODULATION 35
4h PSK WAVEFORM 36
4i THE GENERATION OF QPSK SIGNAL 37
4j OQPSK WAVEFORM (HALF SYMBOL OFFSET) 38
4k GENERATION ON OQPSK SIGNAL 39
41 GENERATION OF MSK WAVEFORM 40
4m OUTPUT WAVEFORM OF MSK SIGNAL 41
x
5a LASER WARNING LABEL 42
6a SIMPLE BLOCK DIAGRAM RS131 LASER COMMUNICATION SYSTEM 43
6b BLOCK DIAGRAM OF RS131 LASER TRANSCEIVER 44
6c SCHEMATIC OF TRANSCEIVER 45
6d PCB LAYOUT 46
6e DB9JUMPERING 48
7a THE HEADER FILE 54
7b THESETI1NG 55
7c BIOSCOM EXAMPLE 56
7d BIOS_SERIALCOM EXAMPLE 57
XI
CHAPTERt
WIRELESS COMMUNICATION AN OVERVIEW
to An Introduction
A communication occurs when there was an infonnation flow The word
telecommunication is derive from the Greek tele far of and communicare to share
[1] The communication is the process of transferring interpreting and processing
infonnation (data) among the people machines and place This process implies that we
need a sender a medium and a receiver to perform infonnation flow Therefore the
telecommunication is the process of exchanging the data of information in any useable
fonn in any natural delivery among two or more user by using radio wire and light and
other mechanical means
1t Wireless Network
Consider a cellular telephone system that provided coverage in a geographical
area as figure ta shown
To provide wireless communication within a region a Radio Base Station (RBS) must be
set up The Radio Base Station will perfonn the function as access point to the mobile
user and a connection with Mobile Switching Center A mobile user connected to base
station through Common Air Interface which can also called Handshaking ProtocoL [2]
The Radio Base Station will connect to mobile Switching Center through landline The
mobile switching center will provide connectivity to Public Switch Telephone Network
The PSTN Switching Center will provide connectivity to global network
The basic concept of a wireless network was to establishing the mobile user to a base
station followed by connection with mobile switch center and from mobile center
connected to global network
1
Mobile SWltchlna Center(MSC) or
Mobile Telephone SWItohlna omce Voice and Data link
(Landline or ~microwave)
Q ~ ~P-
PSTN
regRadio Link air interface
Figure la The Block Diagram of a Typical Wireless Network [ 2 ]
PSTN network and mobile network will connect by either fix-line or radio wave For the
fixmiddotline It will be twisted copper cable coaxial cable fiber optics cable For the radio
wave it either use microwave and satellite link The characteristic of a PSTN network is
the user was fix at one location while the mobile network allowed the user to move
within the coverage area The process of moving within the coverage area called
Roaming
12 Fundamental of a Wireless Intemet System
To accessing the internet a cellular user need to use a PCMCIA card with the adapter to
connected to laptop in the area where PSTN line was not accessible For example the
product of Celcom Data2Go for wireless data communication can have the following
function shy
e Electronic mail system
e Sending and receiving fax
2
bull Accessing Company database
bull Submit customer order
bull On-line information service
bull accessing Internet-surfing into Netscape
bull terminal mode- billinwregistration
The network ofData2Go by Celcomtradeas shown shy
Figure Ib Celcomtrade Data2Go Network 14 I
Software uses for this type ofnetwork are
bull Delrina WinFaxPro
bull Microsoft Mail
bull Netscape
bull Lotus Notes
13 The purpose of this paper
The main purpose of this project is to develop a useable technique that suitable for
sending data wireless via RS232 communication port The system component will consist
of a desktop computer that act as input device a standard RS232 interface a transceiver
for transmit and receive signal and a modify laser poniter The suggested system will be
3
set and tested in a point-to-point configuration As the figure show below the network
diagram stated shy
J -~HJj----tcooo ~ IEco~codl---=RS=232=--_~ Personal computer Signal RS232 Laser Transceiver RS2321aser Transceiver Personal computer
Figure lc The Simples point to point data communication via RS131laser transceiver
4
Cbapter2
RS-232 INTERFACE AND SERIAL COMMUNICATION
20 Overview
RS 232 Interface in a simple universal well knows data interface RS means
Recommended Standard1 The female connector attaches to Data Communication
Equipment and male connector attaches to Data Terminal Equipment Mostly today PCs
are equipped with two RS232 ports via COMI or COM2 The additional COM port
COM3 and COM4 required additional card
RS-232 defines 25-pin communication line Every line has their own function to
accessing data The configurations ofevery pin layout are show in figure 2a
Normally The ground signal refers to pin 7 Two computers can communicate by using a
null modem A null modem is a special made direct cable and connector It is functioning
like a modem but has limited transmission range Figure 2b illustrated the common
method to wiring a null modem Pin2 and pin3 are wire together and all the cables are
connect in such a way a modem simulated between two computers
The electrical characteristic define by RS232 as
(a) Total capacitance not less than 2500 pF
(b) (b) A binary high logic output lines is + 5to + 15 volts input lines is from +3
to + 15 volts
(c) A binary low logic output lines is from -5 to -15 volts input lines is from -3
to -15 volts
(d) output lines voltages -5 and +5 -3 and +3 volts for input lines are undefined
5
Shelld~ Secondary
tntnsmltted data Transmlttins
Signal element timlne (DCEoTE)
Secondary
Relcetver received data
Signal tlmlne(DCEoTE) Looak
Loopok Secondary
Request To8end
DTERudy
Rem_ Loopb8ok amp Signal Qua
Decmlctor RinS indicator
l reg
Transmitted Data
Request to Send
DCEReady
Rivedline 818nal Detector
Reserved (Testing)
Secondary Received Lne Signel Detector
Recetve Data
reg
Crto8ent
Signal Ground Comman RetUrn
reg Rrved (Testing)
Datas18nal
I 10
rate ct UnusedTnulSmitter signal Signed
element -f
timing (DTE-DCE) bull Tnt Mode 8eooundary~ 13 c
To8ent~
Figure 2a The RS232 pin configuration [81
Pin Number Line Line Pin Number
2 m m 2
3 RD RD 3
4 RTS RTS 4
5 CTS CTS 5
6 DSR---- DSR 6
7 Common 7
8 DCD DCD 8
20 DTR DTR 20
22 R1 R1 22
Figure 2b A Null Modem Configuration [8]
6
21 The Explanation For RS1Jl Pin Abbreviation
Hence is the detail ofeach line in DB9 and DB25 function
Clear to Send (CTS)
Data Carrier Detect (OCR)
Data Set Ready (DSR)
Data Terminal Ready (DTR)
Receive Data (RO)
Ring Indicator (RI)
Requested to Send (RTS)
Transmit Data (TD)
asserted (logic state 1) by DCE it is ready to receive data
logic state 1 whenever there is data link in progress
logic state 1 when DCE is ready to communicated withDTE
logic state 1 when DTE is ready to communicated withDCE
use by DCE to send data to DTE
logic 1 by DCE when a ring is detect
logic state 1 by DTE when it want to transmit data toDCE
Use by DTE to send data to DCE
Figure lc The Detail Explanation of Abbreviation [ 8]
22 UART
UART Universal Asynchronous Receiver Transmitter is a special hardware in RS232
serial interface It sometime called as Asynchronous Communication Element
Most of the new personal computer today is equip with 16450 and 16550 UART The
function ofUART chip is to convert the parallel data to a serial data format that enable a
serial communication between two computers The UART chip also uses to convert back
7
the serial bits to parallel bits format The operation of UART mostly control by one or
more register The process of read writes data to register are through input and output
ports Figure ld showing the address of a UART for COMI and COM4
The UART have FIFO or First in First out buffer FIFO bring the meaning as the first
data to enter the buffer are first to leave The function of buffer is to hold data temporary
before it was feed to the transmission medium The modem 16550A UART have16 bytes
FIFO This means 16 bytes can be writes to UART before anything was overwrite The
16550 UART was necessary for a high-speed communication under windows or
application running under window environment
Serial port Base Register Port Address
COM 1 3F8H COM2 2F8H COM3 3E8H COM3 2E8H
Figure ld The Serial Port Base Register Port [7 ]
23 Serial Communication
Serial communication is transmission of data over a serial interface one data bit at a time
In other word data are transfer through and forth over a single wire Therefore serial
communication is more cost effective than parallel communication RS232 is an example
for serial communication interface
24 Parallel Interface
Parallel communication is a way to sending more than one data at a time (normally eight
data bits) over to a parallel device or a Com Port For an example a computer will send
eight data bits of information to a parallel printer A very simple diagram of parallel
communication was present as Figure 2e The parallel interfaces require separated wire
8
------_------------__shyp
for sending separated data and therefor allowed faster and efficient data transmission On
the other hand to setting up a parallel communication network will be more costly than
serial communication network
1 Printer Interface
1 3 4 5 6 7 8
1 Computer Interface
2 3 4 5 6 7 8
Figure 2e A parallel Printer to Computer Interface [7 ]
25 Asynchronous and synchronous data
For two devices to communicate a way of synchronizing data must be set There are two
way ofdata formatting by using either asynchronous or synchronous
The synchronous operation is such a way that for each line data transmit it has a
separated clock to synchronous that data on a time of period For example data are
transfer once in each direction to and from the computer The synchronous data format
was show in figure 2f
While the asynchronous data is such a way that data are synchronous without clock
Each time the data are transmitting the receiver need to figure out how fast the data is
running The frame of asynchronous data has start and stops bit In another world the
frame always added with additional start and stop bit The asynchronous data format was
show in figure 2g
9
01100011100 o 1 1 1 11 0 0 0 0 001 0110 1 1 0
Unique Code
Continuous Block
Direction offlow
Figure 2f Synchronous data format I 8 ]
Start Stop d7 d6 d5 d4 d3 d2 dl dO Start
1 0 1 0 1 1 0 0I 1 I IMSB LSB
Start bit Stop bit1 Data-bits 1 I
r space mark mark space mark space mark mark space space
Serial Communication
Figure 2g Asynchronous Data Format Adopted form [8]
26 The Start Parity and Stop bits
For two machines to communicate to each other first thing both machines must agree on
the rate of speed for data transfer Second thing is the data must fonnatted for
synchronous or asynchronous operation Therefor for asynchronous operation the data
fonnatted in such a way that contains start and stop bit
271 Start bit
10
The TD line at interface device (Pin3) will go high when no data been transmit To start
transmit a data Transmit serial device will set TD line to low by means ofa start bit The
synchronous operation of DCE is waiting the TD line sign change from high bit to low
bit than DCE pauses half of a bit time and start sampling the incoming data until all the
character has been completely transmit To maintain synchronimtion DCE always
sampling the incoming data string at middle ofeach bit
272 Data bits
The data bits are the bits that contain character Nonnallyone character contains eight
bits Hence is the data bits showing character Amiddot 4tH
l start bit 41----shy Data bits j
shy
I t I Io 0 0 0 0 0
1 1deg1 1
Figure 2h The Data bits Format ( 7 ]
273 Parity bits
Four basic fonns ofparity bits are NONE EVEN ODD MARK and SPACE NONE use
for transmits a character without parity bit EVEN parity use to indicate by send logic 1
after a character if there is an odd number of logic 1 bit after a character data bit
Otherwise logic for EVEN parity goes to zero Odd parity will indicate by sending logic
1 after a data of a character bits if there is an even number of logic 1 after a characters
data bits Otherwise logic for ODD parity goes to zero Mark is logic 1 parity bit after a
data character and SPACE is logic zero after the data character
11
274 Stop bits
The stop bit indicated the end of a character The serial device was always send logic 1
for stop bit
28 Data Transmit and Receive Process
281 Transmit of a character
Several steps take before characters are transmitting from processor to modem
For an example communication between processor and 8251A USART
First the processor configures UART according to the communication protocol
Second an instruction was send to UART and set the flag TxEN Next The processor
was send the character to the data buffer ofUART Then this data buffer transfer the
character to transmit buffer for preparation for transmission Once data buffer was
complete transfer the character and ready to receive a new character the TXRDY flag
will set When processor automatically write in data buffer TXRDY flag automatically
reset
Next RTS (Ready to Send)pin output pin ofUART will alerted by modem that the bits
are about to transmit RTS pin for UART is tie together with modem RTS pin while the
modem realizes about to receive character from UART CTS pin will activated Then the
character was automatically transfer to modem The internal flag TxEMPTY will set
once the character was completely transmit from UART to modem
282 Receive of a character
The process of data receiving was also take several sequence First processor configures
UART according to standard protocol Then to receive a character the processor sends a
12
p
instruction to activated the RxE flag Next DART need to be alerted about the data going
to be transmitted DSR (Data Set Ready) will activated DSR pin of DART and modem
are tied together therefore when processor read this flags and realizes that the modem
has characters to be transmitted to DART Once DSR signal been set processor set DTR
(data terminal ready) to high And once DTR pin is asserted characters was
automatically transfer out from modem Once the characters is receive by DART it
formatted the data according to their start stop parity bits The RxRDY activated when a
character was completely receive
The bock diagram ofDART was show in ftgUre 2i
transmittedT~_B_r ~Mode Register
Transmit Register-~ I I data
I [_~~~J lt-~--r I
Receiver Register L~~~l-~~mmg =71 -_Rece~~I_v-e_r-B_-un_e=r=_-_ ~_romL--_
Devices and bullControl LogiC
l Internal Transmitter I Bus c-- ~ Clocking
--_______________rece_i_ve_r__lt=__-T Circuitary
Figure 2i USART Bloek Diagram [8 ]
28 COM Port setting
COM Port is the port that allowed computer to communicated with other device
such as modem or printer The standard personal computer normally has four
communications port COM 1 and COM 2 are assign for external port All the
13
LIST OF ILLUSTRATION
Figure Page
18 THE BLOCK DIAGRAM OF TYPICAL NETWORK 2
Ib CELCOMtrade DATA2GONETWORK
Ie SIMPLEST POINT-TO-POINT DATA COMMUNICATION VIA
2
RS232 LASER TRANSCEIVER 4
28 THE RS232 PIN CONFIGURATION 6
2b A NULL MODEM CONFIGURATION 6
2e DETAIL EXPLANATION OF RS232 PIN ABBREVIATION 7
2d THE SERIAL PORT BASE REGISTER 8
2e A PARALLEL PRINTER TO COMPUTER CONFIGURATION 9
2f SYNCHRONOUS DATA FORMAT 10
2g ASYNCBRONOUS DATA FORMAT 10
2h THE DATA BIT FORMAT 11
2i USART BLOCK DIAGRAM 13
3a ELECTRIC AND MAGNETIC FIELD IN PLANE ELECTROMAGNETIC WAVE 16
3b ILLUSTRATION OF ENERGY DIAGRAM FOR TWO LEVEL ENERGY SYSTEM ABSORPTION STIMULATED EMISSION 19 SPONTANEOUS EMISSION
3e SPATIAL COHERENT AT FOCUSING POINT 20
IX
po
3d EXCITATION OF GASEOUS LASER MEDIUM REFLECTION 21 OF PHOTON DURING STIMULATED EMISSION EXITING PHOTON IN LASER BEAM
SIGNAL (C) INTENSITY OF LIGHT
3e SCHEMATIC DIAGRAM FOR AN END PUMPED ND YAGLASER 22
3f THE ELECTROMAGNETIC SPECTRUM 23
3g AMPLITUDE MODULATION OF OPTICAL LIGHT BEAM 24
3h NON RETURN ZERO FORMAT 24
3i RETURN TO ZERO FORMAT 24
3j USING FM MODULATION TO MODULATED INTENSITY OF tiGHT (A) MASSAGE AMPUTUDE (B) FM MODULATION 25
4a AM SIGNAL MODULATION 30
4b FM SIGNAL MODULATION 31
4c FREQUENCY MODULATION 32
4d FSKFORMAT 33
4e FORMATION OF FSK SIGNAL 34
4f NON COHERENT DEMODULATION 35
4g COHERENT DEMODULATION 35
4h PSK WAVEFORM 36
4i THE GENERATION OF QPSK SIGNAL 37
4j OQPSK WAVEFORM (HALF SYMBOL OFFSET) 38
4k GENERATION ON OQPSK SIGNAL 39
41 GENERATION OF MSK WAVEFORM 40
4m OUTPUT WAVEFORM OF MSK SIGNAL 41
x
5a LASER WARNING LABEL 42
6a SIMPLE BLOCK DIAGRAM RS131 LASER COMMUNICATION SYSTEM 43
6b BLOCK DIAGRAM OF RS131 LASER TRANSCEIVER 44
6c SCHEMATIC OF TRANSCEIVER 45
6d PCB LAYOUT 46
6e DB9JUMPERING 48
7a THE HEADER FILE 54
7b THESETI1NG 55
7c BIOSCOM EXAMPLE 56
7d BIOS_SERIALCOM EXAMPLE 57
XI
CHAPTERt
WIRELESS COMMUNICATION AN OVERVIEW
to An Introduction
A communication occurs when there was an infonnation flow The word
telecommunication is derive from the Greek tele far of and communicare to share
[1] The communication is the process of transferring interpreting and processing
infonnation (data) among the people machines and place This process implies that we
need a sender a medium and a receiver to perform infonnation flow Therefore the
telecommunication is the process of exchanging the data of information in any useable
fonn in any natural delivery among two or more user by using radio wire and light and
other mechanical means
1t Wireless Network
Consider a cellular telephone system that provided coverage in a geographical
area as figure ta shown
To provide wireless communication within a region a Radio Base Station (RBS) must be
set up The Radio Base Station will perfonn the function as access point to the mobile
user and a connection with Mobile Switching Center A mobile user connected to base
station through Common Air Interface which can also called Handshaking ProtocoL [2]
The Radio Base Station will connect to mobile Switching Center through landline The
mobile switching center will provide connectivity to Public Switch Telephone Network
The PSTN Switching Center will provide connectivity to global network
The basic concept of a wireless network was to establishing the mobile user to a base
station followed by connection with mobile switch center and from mobile center
connected to global network
1
Mobile SWltchlna Center(MSC) or
Mobile Telephone SWItohlna omce Voice and Data link
(Landline or ~microwave)
Q ~ ~P-
PSTN
regRadio Link air interface
Figure la The Block Diagram of a Typical Wireless Network [ 2 ]
PSTN network and mobile network will connect by either fix-line or radio wave For the
fixmiddotline It will be twisted copper cable coaxial cable fiber optics cable For the radio
wave it either use microwave and satellite link The characteristic of a PSTN network is
the user was fix at one location while the mobile network allowed the user to move
within the coverage area The process of moving within the coverage area called
Roaming
12 Fundamental of a Wireless Intemet System
To accessing the internet a cellular user need to use a PCMCIA card with the adapter to
connected to laptop in the area where PSTN line was not accessible For example the
product of Celcom Data2Go for wireless data communication can have the following
function shy
e Electronic mail system
e Sending and receiving fax
2
bull Accessing Company database
bull Submit customer order
bull On-line information service
bull accessing Internet-surfing into Netscape
bull terminal mode- billinwregistration
The network ofData2Go by Celcomtradeas shown shy
Figure Ib Celcomtrade Data2Go Network 14 I
Software uses for this type ofnetwork are
bull Delrina WinFaxPro
bull Microsoft Mail
bull Netscape
bull Lotus Notes
13 The purpose of this paper
The main purpose of this project is to develop a useable technique that suitable for
sending data wireless via RS232 communication port The system component will consist
of a desktop computer that act as input device a standard RS232 interface a transceiver
for transmit and receive signal and a modify laser poniter The suggested system will be
3
set and tested in a point-to-point configuration As the figure show below the network
diagram stated shy
J -~HJj----tcooo ~ IEco~codl---=RS=232=--_~ Personal computer Signal RS232 Laser Transceiver RS2321aser Transceiver Personal computer
Figure lc The Simples point to point data communication via RS131laser transceiver
4
Cbapter2
RS-232 INTERFACE AND SERIAL COMMUNICATION
20 Overview
RS 232 Interface in a simple universal well knows data interface RS means
Recommended Standard1 The female connector attaches to Data Communication
Equipment and male connector attaches to Data Terminal Equipment Mostly today PCs
are equipped with two RS232 ports via COMI or COM2 The additional COM port
COM3 and COM4 required additional card
RS-232 defines 25-pin communication line Every line has their own function to
accessing data The configurations ofevery pin layout are show in figure 2a
Normally The ground signal refers to pin 7 Two computers can communicate by using a
null modem A null modem is a special made direct cable and connector It is functioning
like a modem but has limited transmission range Figure 2b illustrated the common
method to wiring a null modem Pin2 and pin3 are wire together and all the cables are
connect in such a way a modem simulated between two computers
The electrical characteristic define by RS232 as
(a) Total capacitance not less than 2500 pF
(b) (b) A binary high logic output lines is + 5to + 15 volts input lines is from +3
to + 15 volts
(c) A binary low logic output lines is from -5 to -15 volts input lines is from -3
to -15 volts
(d) output lines voltages -5 and +5 -3 and +3 volts for input lines are undefined
5
Shelld~ Secondary
tntnsmltted data Transmlttins
Signal element timlne (DCEoTE)
Secondary
Relcetver received data
Signal tlmlne(DCEoTE) Looak
Loopok Secondary
Request To8end
DTERudy
Rem_ Loopb8ok amp Signal Qua
Decmlctor RinS indicator
l reg
Transmitted Data
Request to Send
DCEReady
Rivedline 818nal Detector
Reserved (Testing)
Secondary Received Lne Signel Detector
Recetve Data
reg
Crto8ent
Signal Ground Comman RetUrn
reg Rrved (Testing)
Datas18nal
I 10
rate ct UnusedTnulSmitter signal Signed
element -f
timing (DTE-DCE) bull Tnt Mode 8eooundary~ 13 c
To8ent~
Figure 2a The RS232 pin configuration [81
Pin Number Line Line Pin Number
2 m m 2
3 RD RD 3
4 RTS RTS 4
5 CTS CTS 5
6 DSR---- DSR 6
7 Common 7
8 DCD DCD 8
20 DTR DTR 20
22 R1 R1 22
Figure 2b A Null Modem Configuration [8]
6
21 The Explanation For RS1Jl Pin Abbreviation
Hence is the detail ofeach line in DB9 and DB25 function
Clear to Send (CTS)
Data Carrier Detect (OCR)
Data Set Ready (DSR)
Data Terminal Ready (DTR)
Receive Data (RO)
Ring Indicator (RI)
Requested to Send (RTS)
Transmit Data (TD)
asserted (logic state 1) by DCE it is ready to receive data
logic state 1 whenever there is data link in progress
logic state 1 when DCE is ready to communicated withDTE
logic state 1 when DTE is ready to communicated withDCE
use by DCE to send data to DTE
logic 1 by DCE when a ring is detect
logic state 1 by DTE when it want to transmit data toDCE
Use by DTE to send data to DCE
Figure lc The Detail Explanation of Abbreviation [ 8]
22 UART
UART Universal Asynchronous Receiver Transmitter is a special hardware in RS232
serial interface It sometime called as Asynchronous Communication Element
Most of the new personal computer today is equip with 16450 and 16550 UART The
function ofUART chip is to convert the parallel data to a serial data format that enable a
serial communication between two computers The UART chip also uses to convert back
7
the serial bits to parallel bits format The operation of UART mostly control by one or
more register The process of read writes data to register are through input and output
ports Figure ld showing the address of a UART for COMI and COM4
The UART have FIFO or First in First out buffer FIFO bring the meaning as the first
data to enter the buffer are first to leave The function of buffer is to hold data temporary
before it was feed to the transmission medium The modem 16550A UART have16 bytes
FIFO This means 16 bytes can be writes to UART before anything was overwrite The
16550 UART was necessary for a high-speed communication under windows or
application running under window environment
Serial port Base Register Port Address
COM 1 3F8H COM2 2F8H COM3 3E8H COM3 2E8H
Figure ld The Serial Port Base Register Port [7 ]
23 Serial Communication
Serial communication is transmission of data over a serial interface one data bit at a time
In other word data are transfer through and forth over a single wire Therefore serial
communication is more cost effective than parallel communication RS232 is an example
for serial communication interface
24 Parallel Interface
Parallel communication is a way to sending more than one data at a time (normally eight
data bits) over to a parallel device or a Com Port For an example a computer will send
eight data bits of information to a parallel printer A very simple diagram of parallel
communication was present as Figure 2e The parallel interfaces require separated wire
8
------_------------__shyp
for sending separated data and therefor allowed faster and efficient data transmission On
the other hand to setting up a parallel communication network will be more costly than
serial communication network
1 Printer Interface
1 3 4 5 6 7 8
1 Computer Interface
2 3 4 5 6 7 8
Figure 2e A parallel Printer to Computer Interface [7 ]
25 Asynchronous and synchronous data
For two devices to communicate a way of synchronizing data must be set There are two
way ofdata formatting by using either asynchronous or synchronous
The synchronous operation is such a way that for each line data transmit it has a
separated clock to synchronous that data on a time of period For example data are
transfer once in each direction to and from the computer The synchronous data format
was show in figure 2f
While the asynchronous data is such a way that data are synchronous without clock
Each time the data are transmitting the receiver need to figure out how fast the data is
running The frame of asynchronous data has start and stops bit In another world the
frame always added with additional start and stop bit The asynchronous data format was
show in figure 2g
9
01100011100 o 1 1 1 11 0 0 0 0 001 0110 1 1 0
Unique Code
Continuous Block
Direction offlow
Figure 2f Synchronous data format I 8 ]
Start Stop d7 d6 d5 d4 d3 d2 dl dO Start
1 0 1 0 1 1 0 0I 1 I IMSB LSB
Start bit Stop bit1 Data-bits 1 I
r space mark mark space mark space mark mark space space
Serial Communication
Figure 2g Asynchronous Data Format Adopted form [8]
26 The Start Parity and Stop bits
For two machines to communicate to each other first thing both machines must agree on
the rate of speed for data transfer Second thing is the data must fonnatted for
synchronous or asynchronous operation Therefor for asynchronous operation the data
fonnatted in such a way that contains start and stop bit
271 Start bit
10
The TD line at interface device (Pin3) will go high when no data been transmit To start
transmit a data Transmit serial device will set TD line to low by means ofa start bit The
synchronous operation of DCE is waiting the TD line sign change from high bit to low
bit than DCE pauses half of a bit time and start sampling the incoming data until all the
character has been completely transmit To maintain synchronimtion DCE always
sampling the incoming data string at middle ofeach bit
272 Data bits
The data bits are the bits that contain character Nonnallyone character contains eight
bits Hence is the data bits showing character Amiddot 4tH
l start bit 41----shy Data bits j
shy
I t I Io 0 0 0 0 0
1 1deg1 1
Figure 2h The Data bits Format ( 7 ]
273 Parity bits
Four basic fonns ofparity bits are NONE EVEN ODD MARK and SPACE NONE use
for transmits a character without parity bit EVEN parity use to indicate by send logic 1
after a character if there is an odd number of logic 1 bit after a character data bit
Otherwise logic for EVEN parity goes to zero Odd parity will indicate by sending logic
1 after a data of a character bits if there is an even number of logic 1 after a characters
data bits Otherwise logic for ODD parity goes to zero Mark is logic 1 parity bit after a
data character and SPACE is logic zero after the data character
11
274 Stop bits
The stop bit indicated the end of a character The serial device was always send logic 1
for stop bit
28 Data Transmit and Receive Process
281 Transmit of a character
Several steps take before characters are transmitting from processor to modem
For an example communication between processor and 8251A USART
First the processor configures UART according to the communication protocol
Second an instruction was send to UART and set the flag TxEN Next The processor
was send the character to the data buffer ofUART Then this data buffer transfer the
character to transmit buffer for preparation for transmission Once data buffer was
complete transfer the character and ready to receive a new character the TXRDY flag
will set When processor automatically write in data buffer TXRDY flag automatically
reset
Next RTS (Ready to Send)pin output pin ofUART will alerted by modem that the bits
are about to transmit RTS pin for UART is tie together with modem RTS pin while the
modem realizes about to receive character from UART CTS pin will activated Then the
character was automatically transfer to modem The internal flag TxEMPTY will set
once the character was completely transmit from UART to modem
282 Receive of a character
The process of data receiving was also take several sequence First processor configures
UART according to standard protocol Then to receive a character the processor sends a
12
p
instruction to activated the RxE flag Next DART need to be alerted about the data going
to be transmitted DSR (Data Set Ready) will activated DSR pin of DART and modem
are tied together therefore when processor read this flags and realizes that the modem
has characters to be transmitted to DART Once DSR signal been set processor set DTR
(data terminal ready) to high And once DTR pin is asserted characters was
automatically transfer out from modem Once the characters is receive by DART it
formatted the data according to their start stop parity bits The RxRDY activated when a
character was completely receive
The bock diagram ofDART was show in ftgUre 2i
transmittedT~_B_r ~Mode Register
Transmit Register-~ I I data
I [_~~~J lt-~--r I
Receiver Register L~~~l-~~mmg =71 -_Rece~~I_v-e_r-B_-un_e=r=_-_ ~_romL--_
Devices and bullControl LogiC
l Internal Transmitter I Bus c-- ~ Clocking
--_______________rece_i_ve_r__lt=__-T Circuitary
Figure 2i USART Bloek Diagram [8 ]
28 COM Port setting
COM Port is the port that allowed computer to communicated with other device
such as modem or printer The standard personal computer normally has four
communications port COM 1 and COM 2 are assign for external port All the
13
po
3d EXCITATION OF GASEOUS LASER MEDIUM REFLECTION 21 OF PHOTON DURING STIMULATED EMISSION EXITING PHOTON IN LASER BEAM
SIGNAL (C) INTENSITY OF LIGHT
3e SCHEMATIC DIAGRAM FOR AN END PUMPED ND YAGLASER 22
3f THE ELECTROMAGNETIC SPECTRUM 23
3g AMPLITUDE MODULATION OF OPTICAL LIGHT BEAM 24
3h NON RETURN ZERO FORMAT 24
3i RETURN TO ZERO FORMAT 24
3j USING FM MODULATION TO MODULATED INTENSITY OF tiGHT (A) MASSAGE AMPUTUDE (B) FM MODULATION 25
4a AM SIGNAL MODULATION 30
4b FM SIGNAL MODULATION 31
4c FREQUENCY MODULATION 32
4d FSKFORMAT 33
4e FORMATION OF FSK SIGNAL 34
4f NON COHERENT DEMODULATION 35
4g COHERENT DEMODULATION 35
4h PSK WAVEFORM 36
4i THE GENERATION OF QPSK SIGNAL 37
4j OQPSK WAVEFORM (HALF SYMBOL OFFSET) 38
4k GENERATION ON OQPSK SIGNAL 39
41 GENERATION OF MSK WAVEFORM 40
4m OUTPUT WAVEFORM OF MSK SIGNAL 41
x
5a LASER WARNING LABEL 42
6a SIMPLE BLOCK DIAGRAM RS131 LASER COMMUNICATION SYSTEM 43
6b BLOCK DIAGRAM OF RS131 LASER TRANSCEIVER 44
6c SCHEMATIC OF TRANSCEIVER 45
6d PCB LAYOUT 46
6e DB9JUMPERING 48
7a THE HEADER FILE 54
7b THESETI1NG 55
7c BIOSCOM EXAMPLE 56
7d BIOS_SERIALCOM EXAMPLE 57
XI
CHAPTERt
WIRELESS COMMUNICATION AN OVERVIEW
to An Introduction
A communication occurs when there was an infonnation flow The word
telecommunication is derive from the Greek tele far of and communicare to share
[1] The communication is the process of transferring interpreting and processing
infonnation (data) among the people machines and place This process implies that we
need a sender a medium and a receiver to perform infonnation flow Therefore the
telecommunication is the process of exchanging the data of information in any useable
fonn in any natural delivery among two or more user by using radio wire and light and
other mechanical means
1t Wireless Network
Consider a cellular telephone system that provided coverage in a geographical
area as figure ta shown
To provide wireless communication within a region a Radio Base Station (RBS) must be
set up The Radio Base Station will perfonn the function as access point to the mobile
user and a connection with Mobile Switching Center A mobile user connected to base
station through Common Air Interface which can also called Handshaking ProtocoL [2]
The Radio Base Station will connect to mobile Switching Center through landline The
mobile switching center will provide connectivity to Public Switch Telephone Network
The PSTN Switching Center will provide connectivity to global network
The basic concept of a wireless network was to establishing the mobile user to a base
station followed by connection with mobile switch center and from mobile center
connected to global network
1
Mobile SWltchlna Center(MSC) or
Mobile Telephone SWItohlna omce Voice and Data link
(Landline or ~microwave)
Q ~ ~P-
PSTN
regRadio Link air interface
Figure la The Block Diagram of a Typical Wireless Network [ 2 ]
PSTN network and mobile network will connect by either fix-line or radio wave For the
fixmiddotline It will be twisted copper cable coaxial cable fiber optics cable For the radio
wave it either use microwave and satellite link The characteristic of a PSTN network is
the user was fix at one location while the mobile network allowed the user to move
within the coverage area The process of moving within the coverage area called
Roaming
12 Fundamental of a Wireless Intemet System
To accessing the internet a cellular user need to use a PCMCIA card with the adapter to
connected to laptop in the area where PSTN line was not accessible For example the
product of Celcom Data2Go for wireless data communication can have the following
function shy
e Electronic mail system
e Sending and receiving fax
2
bull Accessing Company database
bull Submit customer order
bull On-line information service
bull accessing Internet-surfing into Netscape
bull terminal mode- billinwregistration
The network ofData2Go by Celcomtradeas shown shy
Figure Ib Celcomtrade Data2Go Network 14 I
Software uses for this type ofnetwork are
bull Delrina WinFaxPro
bull Microsoft Mail
bull Netscape
bull Lotus Notes
13 The purpose of this paper
The main purpose of this project is to develop a useable technique that suitable for
sending data wireless via RS232 communication port The system component will consist
of a desktop computer that act as input device a standard RS232 interface a transceiver
for transmit and receive signal and a modify laser poniter The suggested system will be
3
set and tested in a point-to-point configuration As the figure show below the network
diagram stated shy
J -~HJj----tcooo ~ IEco~codl---=RS=232=--_~ Personal computer Signal RS232 Laser Transceiver RS2321aser Transceiver Personal computer
Figure lc The Simples point to point data communication via RS131laser transceiver
4
Cbapter2
RS-232 INTERFACE AND SERIAL COMMUNICATION
20 Overview
RS 232 Interface in a simple universal well knows data interface RS means
Recommended Standard1 The female connector attaches to Data Communication
Equipment and male connector attaches to Data Terminal Equipment Mostly today PCs
are equipped with two RS232 ports via COMI or COM2 The additional COM port
COM3 and COM4 required additional card
RS-232 defines 25-pin communication line Every line has their own function to
accessing data The configurations ofevery pin layout are show in figure 2a
Normally The ground signal refers to pin 7 Two computers can communicate by using a
null modem A null modem is a special made direct cable and connector It is functioning
like a modem but has limited transmission range Figure 2b illustrated the common
method to wiring a null modem Pin2 and pin3 are wire together and all the cables are
connect in such a way a modem simulated between two computers
The electrical characteristic define by RS232 as
(a) Total capacitance not less than 2500 pF
(b) (b) A binary high logic output lines is + 5to + 15 volts input lines is from +3
to + 15 volts
(c) A binary low logic output lines is from -5 to -15 volts input lines is from -3
to -15 volts
(d) output lines voltages -5 and +5 -3 and +3 volts for input lines are undefined
5
Shelld~ Secondary
tntnsmltted data Transmlttins
Signal element timlne (DCEoTE)
Secondary
Relcetver received data
Signal tlmlne(DCEoTE) Looak
Loopok Secondary
Request To8end
DTERudy
Rem_ Loopb8ok amp Signal Qua
Decmlctor RinS indicator
l reg
Transmitted Data
Request to Send
DCEReady
Rivedline 818nal Detector
Reserved (Testing)
Secondary Received Lne Signel Detector
Recetve Data
reg
Crto8ent
Signal Ground Comman RetUrn
reg Rrved (Testing)
Datas18nal
I 10
rate ct UnusedTnulSmitter signal Signed
element -f
timing (DTE-DCE) bull Tnt Mode 8eooundary~ 13 c
To8ent~
Figure 2a The RS232 pin configuration [81
Pin Number Line Line Pin Number
2 m m 2
3 RD RD 3
4 RTS RTS 4
5 CTS CTS 5
6 DSR---- DSR 6
7 Common 7
8 DCD DCD 8
20 DTR DTR 20
22 R1 R1 22
Figure 2b A Null Modem Configuration [8]
6
21 The Explanation For RS1Jl Pin Abbreviation
Hence is the detail ofeach line in DB9 and DB25 function
Clear to Send (CTS)
Data Carrier Detect (OCR)
Data Set Ready (DSR)
Data Terminal Ready (DTR)
Receive Data (RO)
Ring Indicator (RI)
Requested to Send (RTS)
Transmit Data (TD)
asserted (logic state 1) by DCE it is ready to receive data
logic state 1 whenever there is data link in progress
logic state 1 when DCE is ready to communicated withDTE
logic state 1 when DTE is ready to communicated withDCE
use by DCE to send data to DTE
logic 1 by DCE when a ring is detect
logic state 1 by DTE when it want to transmit data toDCE
Use by DTE to send data to DCE
Figure lc The Detail Explanation of Abbreviation [ 8]
22 UART
UART Universal Asynchronous Receiver Transmitter is a special hardware in RS232
serial interface It sometime called as Asynchronous Communication Element
Most of the new personal computer today is equip with 16450 and 16550 UART The
function ofUART chip is to convert the parallel data to a serial data format that enable a
serial communication between two computers The UART chip also uses to convert back
7
the serial bits to parallel bits format The operation of UART mostly control by one or
more register The process of read writes data to register are through input and output
ports Figure ld showing the address of a UART for COMI and COM4
The UART have FIFO or First in First out buffer FIFO bring the meaning as the first
data to enter the buffer are first to leave The function of buffer is to hold data temporary
before it was feed to the transmission medium The modem 16550A UART have16 bytes
FIFO This means 16 bytes can be writes to UART before anything was overwrite The
16550 UART was necessary for a high-speed communication under windows or
application running under window environment
Serial port Base Register Port Address
COM 1 3F8H COM2 2F8H COM3 3E8H COM3 2E8H
Figure ld The Serial Port Base Register Port [7 ]
23 Serial Communication
Serial communication is transmission of data over a serial interface one data bit at a time
In other word data are transfer through and forth over a single wire Therefore serial
communication is more cost effective than parallel communication RS232 is an example
for serial communication interface
24 Parallel Interface
Parallel communication is a way to sending more than one data at a time (normally eight
data bits) over to a parallel device or a Com Port For an example a computer will send
eight data bits of information to a parallel printer A very simple diagram of parallel
communication was present as Figure 2e The parallel interfaces require separated wire
8
------_------------__shyp
for sending separated data and therefor allowed faster and efficient data transmission On
the other hand to setting up a parallel communication network will be more costly than
serial communication network
1 Printer Interface
1 3 4 5 6 7 8
1 Computer Interface
2 3 4 5 6 7 8
Figure 2e A parallel Printer to Computer Interface [7 ]
25 Asynchronous and synchronous data
For two devices to communicate a way of synchronizing data must be set There are two
way ofdata formatting by using either asynchronous or synchronous
The synchronous operation is such a way that for each line data transmit it has a
separated clock to synchronous that data on a time of period For example data are
transfer once in each direction to and from the computer The synchronous data format
was show in figure 2f
While the asynchronous data is such a way that data are synchronous without clock
Each time the data are transmitting the receiver need to figure out how fast the data is
running The frame of asynchronous data has start and stops bit In another world the
frame always added with additional start and stop bit The asynchronous data format was
show in figure 2g
9
01100011100 o 1 1 1 11 0 0 0 0 001 0110 1 1 0
Unique Code
Continuous Block
Direction offlow
Figure 2f Synchronous data format I 8 ]
Start Stop d7 d6 d5 d4 d3 d2 dl dO Start
1 0 1 0 1 1 0 0I 1 I IMSB LSB
Start bit Stop bit1 Data-bits 1 I
r space mark mark space mark space mark mark space space
Serial Communication
Figure 2g Asynchronous Data Format Adopted form [8]
26 The Start Parity and Stop bits
For two machines to communicate to each other first thing both machines must agree on
the rate of speed for data transfer Second thing is the data must fonnatted for
synchronous or asynchronous operation Therefor for asynchronous operation the data
fonnatted in such a way that contains start and stop bit
271 Start bit
10
The TD line at interface device (Pin3) will go high when no data been transmit To start
transmit a data Transmit serial device will set TD line to low by means ofa start bit The
synchronous operation of DCE is waiting the TD line sign change from high bit to low
bit than DCE pauses half of a bit time and start sampling the incoming data until all the
character has been completely transmit To maintain synchronimtion DCE always
sampling the incoming data string at middle ofeach bit
272 Data bits
The data bits are the bits that contain character Nonnallyone character contains eight
bits Hence is the data bits showing character Amiddot 4tH
l start bit 41----shy Data bits j
shy
I t I Io 0 0 0 0 0
1 1deg1 1
Figure 2h The Data bits Format ( 7 ]
273 Parity bits
Four basic fonns ofparity bits are NONE EVEN ODD MARK and SPACE NONE use
for transmits a character without parity bit EVEN parity use to indicate by send logic 1
after a character if there is an odd number of logic 1 bit after a character data bit
Otherwise logic for EVEN parity goes to zero Odd parity will indicate by sending logic
1 after a data of a character bits if there is an even number of logic 1 after a characters
data bits Otherwise logic for ODD parity goes to zero Mark is logic 1 parity bit after a
data character and SPACE is logic zero after the data character
11
274 Stop bits
The stop bit indicated the end of a character The serial device was always send logic 1
for stop bit
28 Data Transmit and Receive Process
281 Transmit of a character
Several steps take before characters are transmitting from processor to modem
For an example communication between processor and 8251A USART
First the processor configures UART according to the communication protocol
Second an instruction was send to UART and set the flag TxEN Next The processor
was send the character to the data buffer ofUART Then this data buffer transfer the
character to transmit buffer for preparation for transmission Once data buffer was
complete transfer the character and ready to receive a new character the TXRDY flag
will set When processor automatically write in data buffer TXRDY flag automatically
reset
Next RTS (Ready to Send)pin output pin ofUART will alerted by modem that the bits
are about to transmit RTS pin for UART is tie together with modem RTS pin while the
modem realizes about to receive character from UART CTS pin will activated Then the
character was automatically transfer to modem The internal flag TxEMPTY will set
once the character was completely transmit from UART to modem
282 Receive of a character
The process of data receiving was also take several sequence First processor configures
UART according to standard protocol Then to receive a character the processor sends a
12
p
instruction to activated the RxE flag Next DART need to be alerted about the data going
to be transmitted DSR (Data Set Ready) will activated DSR pin of DART and modem
are tied together therefore when processor read this flags and realizes that the modem
has characters to be transmitted to DART Once DSR signal been set processor set DTR
(data terminal ready) to high And once DTR pin is asserted characters was
automatically transfer out from modem Once the characters is receive by DART it
formatted the data according to their start stop parity bits The RxRDY activated when a
character was completely receive
The bock diagram ofDART was show in ftgUre 2i
transmittedT~_B_r ~Mode Register
Transmit Register-~ I I data
I [_~~~J lt-~--r I
Receiver Register L~~~l-~~mmg =71 -_Rece~~I_v-e_r-B_-un_e=r=_-_ ~_romL--_
Devices and bullControl LogiC
l Internal Transmitter I Bus c-- ~ Clocking
--_______________rece_i_ve_r__lt=__-T Circuitary
Figure 2i USART Bloek Diagram [8 ]
28 COM Port setting
COM Port is the port that allowed computer to communicated with other device
such as modem or printer The standard personal computer normally has four
communications port COM 1 and COM 2 are assign for external port All the
13
5a LASER WARNING LABEL 42
6a SIMPLE BLOCK DIAGRAM RS131 LASER COMMUNICATION SYSTEM 43
6b BLOCK DIAGRAM OF RS131 LASER TRANSCEIVER 44
6c SCHEMATIC OF TRANSCEIVER 45
6d PCB LAYOUT 46
6e DB9JUMPERING 48
7a THE HEADER FILE 54
7b THESETI1NG 55
7c BIOSCOM EXAMPLE 56
7d BIOS_SERIALCOM EXAMPLE 57
XI
CHAPTERt
WIRELESS COMMUNICATION AN OVERVIEW
to An Introduction
A communication occurs when there was an infonnation flow The word
telecommunication is derive from the Greek tele far of and communicare to share
[1] The communication is the process of transferring interpreting and processing
infonnation (data) among the people machines and place This process implies that we
need a sender a medium and a receiver to perform infonnation flow Therefore the
telecommunication is the process of exchanging the data of information in any useable
fonn in any natural delivery among two or more user by using radio wire and light and
other mechanical means
1t Wireless Network
Consider a cellular telephone system that provided coverage in a geographical
area as figure ta shown
To provide wireless communication within a region a Radio Base Station (RBS) must be
set up The Radio Base Station will perfonn the function as access point to the mobile
user and a connection with Mobile Switching Center A mobile user connected to base
station through Common Air Interface which can also called Handshaking ProtocoL [2]
The Radio Base Station will connect to mobile Switching Center through landline The
mobile switching center will provide connectivity to Public Switch Telephone Network
The PSTN Switching Center will provide connectivity to global network
The basic concept of a wireless network was to establishing the mobile user to a base
station followed by connection with mobile switch center and from mobile center
connected to global network
1
Mobile SWltchlna Center(MSC) or
Mobile Telephone SWItohlna omce Voice and Data link
(Landline or ~microwave)
Q ~ ~P-
PSTN
regRadio Link air interface
Figure la The Block Diagram of a Typical Wireless Network [ 2 ]
PSTN network and mobile network will connect by either fix-line or radio wave For the
fixmiddotline It will be twisted copper cable coaxial cable fiber optics cable For the radio
wave it either use microwave and satellite link The characteristic of a PSTN network is
the user was fix at one location while the mobile network allowed the user to move
within the coverage area The process of moving within the coverage area called
Roaming
12 Fundamental of a Wireless Intemet System
To accessing the internet a cellular user need to use a PCMCIA card with the adapter to
connected to laptop in the area where PSTN line was not accessible For example the
product of Celcom Data2Go for wireless data communication can have the following
function shy
e Electronic mail system
e Sending and receiving fax
2
bull Accessing Company database
bull Submit customer order
bull On-line information service
bull accessing Internet-surfing into Netscape
bull terminal mode- billinwregistration
The network ofData2Go by Celcomtradeas shown shy
Figure Ib Celcomtrade Data2Go Network 14 I
Software uses for this type ofnetwork are
bull Delrina WinFaxPro
bull Microsoft Mail
bull Netscape
bull Lotus Notes
13 The purpose of this paper
The main purpose of this project is to develop a useable technique that suitable for
sending data wireless via RS232 communication port The system component will consist
of a desktop computer that act as input device a standard RS232 interface a transceiver
for transmit and receive signal and a modify laser poniter The suggested system will be
3
set and tested in a point-to-point configuration As the figure show below the network
diagram stated shy
J -~HJj----tcooo ~ IEco~codl---=RS=232=--_~ Personal computer Signal RS232 Laser Transceiver RS2321aser Transceiver Personal computer
Figure lc The Simples point to point data communication via RS131laser transceiver
4
Cbapter2
RS-232 INTERFACE AND SERIAL COMMUNICATION
20 Overview
RS 232 Interface in a simple universal well knows data interface RS means
Recommended Standard1 The female connector attaches to Data Communication
Equipment and male connector attaches to Data Terminal Equipment Mostly today PCs
are equipped with two RS232 ports via COMI or COM2 The additional COM port
COM3 and COM4 required additional card
RS-232 defines 25-pin communication line Every line has their own function to
accessing data The configurations ofevery pin layout are show in figure 2a
Normally The ground signal refers to pin 7 Two computers can communicate by using a
null modem A null modem is a special made direct cable and connector It is functioning
like a modem but has limited transmission range Figure 2b illustrated the common
method to wiring a null modem Pin2 and pin3 are wire together and all the cables are
connect in such a way a modem simulated between two computers
The electrical characteristic define by RS232 as
(a) Total capacitance not less than 2500 pF
(b) (b) A binary high logic output lines is + 5to + 15 volts input lines is from +3
to + 15 volts
(c) A binary low logic output lines is from -5 to -15 volts input lines is from -3
to -15 volts
(d) output lines voltages -5 and +5 -3 and +3 volts for input lines are undefined
5
Shelld~ Secondary
tntnsmltted data Transmlttins
Signal element timlne (DCEoTE)
Secondary
Relcetver received data
Signal tlmlne(DCEoTE) Looak
Loopok Secondary
Request To8end
DTERudy
Rem_ Loopb8ok amp Signal Qua
Decmlctor RinS indicator
l reg
Transmitted Data
Request to Send
DCEReady
Rivedline 818nal Detector
Reserved (Testing)
Secondary Received Lne Signel Detector
Recetve Data
reg
Crto8ent
Signal Ground Comman RetUrn
reg Rrved (Testing)
Datas18nal
I 10
rate ct UnusedTnulSmitter signal Signed
element -f
timing (DTE-DCE) bull Tnt Mode 8eooundary~ 13 c
To8ent~
Figure 2a The RS232 pin configuration [81
Pin Number Line Line Pin Number
2 m m 2
3 RD RD 3
4 RTS RTS 4
5 CTS CTS 5
6 DSR---- DSR 6
7 Common 7
8 DCD DCD 8
20 DTR DTR 20
22 R1 R1 22
Figure 2b A Null Modem Configuration [8]
6
21 The Explanation For RS1Jl Pin Abbreviation
Hence is the detail ofeach line in DB9 and DB25 function
Clear to Send (CTS)
Data Carrier Detect (OCR)
Data Set Ready (DSR)
Data Terminal Ready (DTR)
Receive Data (RO)
Ring Indicator (RI)
Requested to Send (RTS)
Transmit Data (TD)
asserted (logic state 1) by DCE it is ready to receive data
logic state 1 whenever there is data link in progress
logic state 1 when DCE is ready to communicated withDTE
logic state 1 when DTE is ready to communicated withDCE
use by DCE to send data to DTE
logic 1 by DCE when a ring is detect
logic state 1 by DTE when it want to transmit data toDCE
Use by DTE to send data to DCE
Figure lc The Detail Explanation of Abbreviation [ 8]
22 UART
UART Universal Asynchronous Receiver Transmitter is a special hardware in RS232
serial interface It sometime called as Asynchronous Communication Element
Most of the new personal computer today is equip with 16450 and 16550 UART The
function ofUART chip is to convert the parallel data to a serial data format that enable a
serial communication between two computers The UART chip also uses to convert back
7
the serial bits to parallel bits format The operation of UART mostly control by one or
more register The process of read writes data to register are through input and output
ports Figure ld showing the address of a UART for COMI and COM4
The UART have FIFO or First in First out buffer FIFO bring the meaning as the first
data to enter the buffer are first to leave The function of buffer is to hold data temporary
before it was feed to the transmission medium The modem 16550A UART have16 bytes
FIFO This means 16 bytes can be writes to UART before anything was overwrite The
16550 UART was necessary for a high-speed communication under windows or
application running under window environment
Serial port Base Register Port Address
COM 1 3F8H COM2 2F8H COM3 3E8H COM3 2E8H
Figure ld The Serial Port Base Register Port [7 ]
23 Serial Communication
Serial communication is transmission of data over a serial interface one data bit at a time
In other word data are transfer through and forth over a single wire Therefore serial
communication is more cost effective than parallel communication RS232 is an example
for serial communication interface
24 Parallel Interface
Parallel communication is a way to sending more than one data at a time (normally eight
data bits) over to a parallel device or a Com Port For an example a computer will send
eight data bits of information to a parallel printer A very simple diagram of parallel
communication was present as Figure 2e The parallel interfaces require separated wire
8
------_------------__shyp
for sending separated data and therefor allowed faster and efficient data transmission On
the other hand to setting up a parallel communication network will be more costly than
serial communication network
1 Printer Interface
1 3 4 5 6 7 8
1 Computer Interface
2 3 4 5 6 7 8
Figure 2e A parallel Printer to Computer Interface [7 ]
25 Asynchronous and synchronous data
For two devices to communicate a way of synchronizing data must be set There are two
way ofdata formatting by using either asynchronous or synchronous
The synchronous operation is such a way that for each line data transmit it has a
separated clock to synchronous that data on a time of period For example data are
transfer once in each direction to and from the computer The synchronous data format
was show in figure 2f
While the asynchronous data is such a way that data are synchronous without clock
Each time the data are transmitting the receiver need to figure out how fast the data is
running The frame of asynchronous data has start and stops bit In another world the
frame always added with additional start and stop bit The asynchronous data format was
show in figure 2g
9
01100011100 o 1 1 1 11 0 0 0 0 001 0110 1 1 0
Unique Code
Continuous Block
Direction offlow
Figure 2f Synchronous data format I 8 ]
Start Stop d7 d6 d5 d4 d3 d2 dl dO Start
1 0 1 0 1 1 0 0I 1 I IMSB LSB
Start bit Stop bit1 Data-bits 1 I
r space mark mark space mark space mark mark space space
Serial Communication
Figure 2g Asynchronous Data Format Adopted form [8]
26 The Start Parity and Stop bits
For two machines to communicate to each other first thing both machines must agree on
the rate of speed for data transfer Second thing is the data must fonnatted for
synchronous or asynchronous operation Therefor for asynchronous operation the data
fonnatted in such a way that contains start and stop bit
271 Start bit
10
The TD line at interface device (Pin3) will go high when no data been transmit To start
transmit a data Transmit serial device will set TD line to low by means ofa start bit The
synchronous operation of DCE is waiting the TD line sign change from high bit to low
bit than DCE pauses half of a bit time and start sampling the incoming data until all the
character has been completely transmit To maintain synchronimtion DCE always
sampling the incoming data string at middle ofeach bit
272 Data bits
The data bits are the bits that contain character Nonnallyone character contains eight
bits Hence is the data bits showing character Amiddot 4tH
l start bit 41----shy Data bits j
shy
I t I Io 0 0 0 0 0
1 1deg1 1
Figure 2h The Data bits Format ( 7 ]
273 Parity bits
Four basic fonns ofparity bits are NONE EVEN ODD MARK and SPACE NONE use
for transmits a character without parity bit EVEN parity use to indicate by send logic 1
after a character if there is an odd number of logic 1 bit after a character data bit
Otherwise logic for EVEN parity goes to zero Odd parity will indicate by sending logic
1 after a data of a character bits if there is an even number of logic 1 after a characters
data bits Otherwise logic for ODD parity goes to zero Mark is logic 1 parity bit after a
data character and SPACE is logic zero after the data character
11
274 Stop bits
The stop bit indicated the end of a character The serial device was always send logic 1
for stop bit
28 Data Transmit and Receive Process
281 Transmit of a character
Several steps take before characters are transmitting from processor to modem
For an example communication between processor and 8251A USART
First the processor configures UART according to the communication protocol
Second an instruction was send to UART and set the flag TxEN Next The processor
was send the character to the data buffer ofUART Then this data buffer transfer the
character to transmit buffer for preparation for transmission Once data buffer was
complete transfer the character and ready to receive a new character the TXRDY flag
will set When processor automatically write in data buffer TXRDY flag automatically
reset
Next RTS (Ready to Send)pin output pin ofUART will alerted by modem that the bits
are about to transmit RTS pin for UART is tie together with modem RTS pin while the
modem realizes about to receive character from UART CTS pin will activated Then the
character was automatically transfer to modem The internal flag TxEMPTY will set
once the character was completely transmit from UART to modem
282 Receive of a character
The process of data receiving was also take several sequence First processor configures
UART according to standard protocol Then to receive a character the processor sends a
12
p
instruction to activated the RxE flag Next DART need to be alerted about the data going
to be transmitted DSR (Data Set Ready) will activated DSR pin of DART and modem
are tied together therefore when processor read this flags and realizes that the modem
has characters to be transmitted to DART Once DSR signal been set processor set DTR
(data terminal ready) to high And once DTR pin is asserted characters was
automatically transfer out from modem Once the characters is receive by DART it
formatted the data according to their start stop parity bits The RxRDY activated when a
character was completely receive
The bock diagram ofDART was show in ftgUre 2i
transmittedT~_B_r ~Mode Register
Transmit Register-~ I I data
I [_~~~J lt-~--r I
Receiver Register L~~~l-~~mmg =71 -_Rece~~I_v-e_r-B_-un_e=r=_-_ ~_romL--_
Devices and bullControl LogiC
l Internal Transmitter I Bus c-- ~ Clocking
--_______________rece_i_ve_r__lt=__-T Circuitary
Figure 2i USART Bloek Diagram [8 ]
28 COM Port setting
COM Port is the port that allowed computer to communicated with other device
such as modem or printer The standard personal computer normally has four
communications port COM 1 and COM 2 are assign for external port All the
13
CHAPTERt
WIRELESS COMMUNICATION AN OVERVIEW
to An Introduction
A communication occurs when there was an infonnation flow The word
telecommunication is derive from the Greek tele far of and communicare to share
[1] The communication is the process of transferring interpreting and processing
infonnation (data) among the people machines and place This process implies that we
need a sender a medium and a receiver to perform infonnation flow Therefore the
telecommunication is the process of exchanging the data of information in any useable
fonn in any natural delivery among two or more user by using radio wire and light and
other mechanical means
1t Wireless Network
Consider a cellular telephone system that provided coverage in a geographical
area as figure ta shown
To provide wireless communication within a region a Radio Base Station (RBS) must be
set up The Radio Base Station will perfonn the function as access point to the mobile
user and a connection with Mobile Switching Center A mobile user connected to base
station through Common Air Interface which can also called Handshaking ProtocoL [2]
The Radio Base Station will connect to mobile Switching Center through landline The
mobile switching center will provide connectivity to Public Switch Telephone Network
The PSTN Switching Center will provide connectivity to global network
The basic concept of a wireless network was to establishing the mobile user to a base
station followed by connection with mobile switch center and from mobile center
connected to global network
1
Mobile SWltchlna Center(MSC) or
Mobile Telephone SWItohlna omce Voice and Data link
(Landline or ~microwave)
Q ~ ~P-
PSTN
regRadio Link air interface
Figure la The Block Diagram of a Typical Wireless Network [ 2 ]
PSTN network and mobile network will connect by either fix-line or radio wave For the
fixmiddotline It will be twisted copper cable coaxial cable fiber optics cable For the radio
wave it either use microwave and satellite link The characteristic of a PSTN network is
the user was fix at one location while the mobile network allowed the user to move
within the coverage area The process of moving within the coverage area called
Roaming
12 Fundamental of a Wireless Intemet System
To accessing the internet a cellular user need to use a PCMCIA card with the adapter to
connected to laptop in the area where PSTN line was not accessible For example the
product of Celcom Data2Go for wireless data communication can have the following
function shy
e Electronic mail system
e Sending and receiving fax
2
bull Accessing Company database
bull Submit customer order
bull On-line information service
bull accessing Internet-surfing into Netscape
bull terminal mode- billinwregistration
The network ofData2Go by Celcomtradeas shown shy
Figure Ib Celcomtrade Data2Go Network 14 I
Software uses for this type ofnetwork are
bull Delrina WinFaxPro
bull Microsoft Mail
bull Netscape
bull Lotus Notes
13 The purpose of this paper
The main purpose of this project is to develop a useable technique that suitable for
sending data wireless via RS232 communication port The system component will consist
of a desktop computer that act as input device a standard RS232 interface a transceiver
for transmit and receive signal and a modify laser poniter The suggested system will be
3
set and tested in a point-to-point configuration As the figure show below the network
diagram stated shy
J -~HJj----tcooo ~ IEco~codl---=RS=232=--_~ Personal computer Signal RS232 Laser Transceiver RS2321aser Transceiver Personal computer
Figure lc The Simples point to point data communication via RS131laser transceiver
4
Cbapter2
RS-232 INTERFACE AND SERIAL COMMUNICATION
20 Overview
RS 232 Interface in a simple universal well knows data interface RS means
Recommended Standard1 The female connector attaches to Data Communication
Equipment and male connector attaches to Data Terminal Equipment Mostly today PCs
are equipped with two RS232 ports via COMI or COM2 The additional COM port
COM3 and COM4 required additional card
RS-232 defines 25-pin communication line Every line has their own function to
accessing data The configurations ofevery pin layout are show in figure 2a
Normally The ground signal refers to pin 7 Two computers can communicate by using a
null modem A null modem is a special made direct cable and connector It is functioning
like a modem but has limited transmission range Figure 2b illustrated the common
method to wiring a null modem Pin2 and pin3 are wire together and all the cables are
connect in such a way a modem simulated between two computers
The electrical characteristic define by RS232 as
(a) Total capacitance not less than 2500 pF
(b) (b) A binary high logic output lines is + 5to + 15 volts input lines is from +3
to + 15 volts
(c) A binary low logic output lines is from -5 to -15 volts input lines is from -3
to -15 volts
(d) output lines voltages -5 and +5 -3 and +3 volts for input lines are undefined
5
Shelld~ Secondary
tntnsmltted data Transmlttins
Signal element timlne (DCEoTE)
Secondary
Relcetver received data
Signal tlmlne(DCEoTE) Looak
Loopok Secondary
Request To8end
DTERudy
Rem_ Loopb8ok amp Signal Qua
Decmlctor RinS indicator
l reg
Transmitted Data
Request to Send
DCEReady
Rivedline 818nal Detector
Reserved (Testing)
Secondary Received Lne Signel Detector
Recetve Data
reg
Crto8ent
Signal Ground Comman RetUrn
reg Rrved (Testing)
Datas18nal
I 10
rate ct UnusedTnulSmitter signal Signed
element -f
timing (DTE-DCE) bull Tnt Mode 8eooundary~ 13 c
To8ent~
Figure 2a The RS232 pin configuration [81
Pin Number Line Line Pin Number
2 m m 2
3 RD RD 3
4 RTS RTS 4
5 CTS CTS 5
6 DSR---- DSR 6
7 Common 7
8 DCD DCD 8
20 DTR DTR 20
22 R1 R1 22
Figure 2b A Null Modem Configuration [8]
6
21 The Explanation For RS1Jl Pin Abbreviation
Hence is the detail ofeach line in DB9 and DB25 function
Clear to Send (CTS)
Data Carrier Detect (OCR)
Data Set Ready (DSR)
Data Terminal Ready (DTR)
Receive Data (RO)
Ring Indicator (RI)
Requested to Send (RTS)
Transmit Data (TD)
asserted (logic state 1) by DCE it is ready to receive data
logic state 1 whenever there is data link in progress
logic state 1 when DCE is ready to communicated withDTE
logic state 1 when DTE is ready to communicated withDCE
use by DCE to send data to DTE
logic 1 by DCE when a ring is detect
logic state 1 by DTE when it want to transmit data toDCE
Use by DTE to send data to DCE
Figure lc The Detail Explanation of Abbreviation [ 8]
22 UART
UART Universal Asynchronous Receiver Transmitter is a special hardware in RS232
serial interface It sometime called as Asynchronous Communication Element
Most of the new personal computer today is equip with 16450 and 16550 UART The
function ofUART chip is to convert the parallel data to a serial data format that enable a
serial communication between two computers The UART chip also uses to convert back
7
the serial bits to parallel bits format The operation of UART mostly control by one or
more register The process of read writes data to register are through input and output
ports Figure ld showing the address of a UART for COMI and COM4
The UART have FIFO or First in First out buffer FIFO bring the meaning as the first
data to enter the buffer are first to leave The function of buffer is to hold data temporary
before it was feed to the transmission medium The modem 16550A UART have16 bytes
FIFO This means 16 bytes can be writes to UART before anything was overwrite The
16550 UART was necessary for a high-speed communication under windows or
application running under window environment
Serial port Base Register Port Address
COM 1 3F8H COM2 2F8H COM3 3E8H COM3 2E8H
Figure ld The Serial Port Base Register Port [7 ]
23 Serial Communication
Serial communication is transmission of data over a serial interface one data bit at a time
In other word data are transfer through and forth over a single wire Therefore serial
communication is more cost effective than parallel communication RS232 is an example
for serial communication interface
24 Parallel Interface
Parallel communication is a way to sending more than one data at a time (normally eight
data bits) over to a parallel device or a Com Port For an example a computer will send
eight data bits of information to a parallel printer A very simple diagram of parallel
communication was present as Figure 2e The parallel interfaces require separated wire
8
------_------------__shyp
for sending separated data and therefor allowed faster and efficient data transmission On
the other hand to setting up a parallel communication network will be more costly than
serial communication network
1 Printer Interface
1 3 4 5 6 7 8
1 Computer Interface
2 3 4 5 6 7 8
Figure 2e A parallel Printer to Computer Interface [7 ]
25 Asynchronous and synchronous data
For two devices to communicate a way of synchronizing data must be set There are two
way ofdata formatting by using either asynchronous or synchronous
The synchronous operation is such a way that for each line data transmit it has a
separated clock to synchronous that data on a time of period For example data are
transfer once in each direction to and from the computer The synchronous data format
was show in figure 2f
While the asynchronous data is such a way that data are synchronous without clock
Each time the data are transmitting the receiver need to figure out how fast the data is
running The frame of asynchronous data has start and stops bit In another world the
frame always added with additional start and stop bit The asynchronous data format was
show in figure 2g
9
01100011100 o 1 1 1 11 0 0 0 0 001 0110 1 1 0
Unique Code
Continuous Block
Direction offlow
Figure 2f Synchronous data format I 8 ]
Start Stop d7 d6 d5 d4 d3 d2 dl dO Start
1 0 1 0 1 1 0 0I 1 I IMSB LSB
Start bit Stop bit1 Data-bits 1 I
r space mark mark space mark space mark mark space space
Serial Communication
Figure 2g Asynchronous Data Format Adopted form [8]
26 The Start Parity and Stop bits
For two machines to communicate to each other first thing both machines must agree on
the rate of speed for data transfer Second thing is the data must fonnatted for
synchronous or asynchronous operation Therefor for asynchronous operation the data
fonnatted in such a way that contains start and stop bit
271 Start bit
10
The TD line at interface device (Pin3) will go high when no data been transmit To start
transmit a data Transmit serial device will set TD line to low by means ofa start bit The
synchronous operation of DCE is waiting the TD line sign change from high bit to low
bit than DCE pauses half of a bit time and start sampling the incoming data until all the
character has been completely transmit To maintain synchronimtion DCE always
sampling the incoming data string at middle ofeach bit
272 Data bits
The data bits are the bits that contain character Nonnallyone character contains eight
bits Hence is the data bits showing character Amiddot 4tH
l start bit 41----shy Data bits j
shy
I t I Io 0 0 0 0 0
1 1deg1 1
Figure 2h The Data bits Format ( 7 ]
273 Parity bits
Four basic fonns ofparity bits are NONE EVEN ODD MARK and SPACE NONE use
for transmits a character without parity bit EVEN parity use to indicate by send logic 1
after a character if there is an odd number of logic 1 bit after a character data bit
Otherwise logic for EVEN parity goes to zero Odd parity will indicate by sending logic
1 after a data of a character bits if there is an even number of logic 1 after a characters
data bits Otherwise logic for ODD parity goes to zero Mark is logic 1 parity bit after a
data character and SPACE is logic zero after the data character
11
274 Stop bits
The stop bit indicated the end of a character The serial device was always send logic 1
for stop bit
28 Data Transmit and Receive Process
281 Transmit of a character
Several steps take before characters are transmitting from processor to modem
For an example communication between processor and 8251A USART
First the processor configures UART according to the communication protocol
Second an instruction was send to UART and set the flag TxEN Next The processor
was send the character to the data buffer ofUART Then this data buffer transfer the
character to transmit buffer for preparation for transmission Once data buffer was
complete transfer the character and ready to receive a new character the TXRDY flag
will set When processor automatically write in data buffer TXRDY flag automatically
reset
Next RTS (Ready to Send)pin output pin ofUART will alerted by modem that the bits
are about to transmit RTS pin for UART is tie together with modem RTS pin while the
modem realizes about to receive character from UART CTS pin will activated Then the
character was automatically transfer to modem The internal flag TxEMPTY will set
once the character was completely transmit from UART to modem
282 Receive of a character
The process of data receiving was also take several sequence First processor configures
UART according to standard protocol Then to receive a character the processor sends a
12
p
instruction to activated the RxE flag Next DART need to be alerted about the data going
to be transmitted DSR (Data Set Ready) will activated DSR pin of DART and modem
are tied together therefore when processor read this flags and realizes that the modem
has characters to be transmitted to DART Once DSR signal been set processor set DTR
(data terminal ready) to high And once DTR pin is asserted characters was
automatically transfer out from modem Once the characters is receive by DART it
formatted the data according to their start stop parity bits The RxRDY activated when a
character was completely receive
The bock diagram ofDART was show in ftgUre 2i
transmittedT~_B_r ~Mode Register
Transmit Register-~ I I data
I [_~~~J lt-~--r I
Receiver Register L~~~l-~~mmg =71 -_Rece~~I_v-e_r-B_-un_e=r=_-_ ~_romL--_
Devices and bullControl LogiC
l Internal Transmitter I Bus c-- ~ Clocking
--_______________rece_i_ve_r__lt=__-T Circuitary
Figure 2i USART Bloek Diagram [8 ]
28 COM Port setting
COM Port is the port that allowed computer to communicated with other device
such as modem or printer The standard personal computer normally has four
communications port COM 1 and COM 2 are assign for external port All the
13
Mobile SWltchlna Center(MSC) or
Mobile Telephone SWItohlna omce Voice and Data link
(Landline or ~microwave)
Q ~ ~P-
PSTN
regRadio Link air interface
Figure la The Block Diagram of a Typical Wireless Network [ 2 ]
PSTN network and mobile network will connect by either fix-line or radio wave For the
fixmiddotline It will be twisted copper cable coaxial cable fiber optics cable For the radio
wave it either use microwave and satellite link The characteristic of a PSTN network is
the user was fix at one location while the mobile network allowed the user to move
within the coverage area The process of moving within the coverage area called
Roaming
12 Fundamental of a Wireless Intemet System
To accessing the internet a cellular user need to use a PCMCIA card with the adapter to
connected to laptop in the area where PSTN line was not accessible For example the
product of Celcom Data2Go for wireless data communication can have the following
function shy
e Electronic mail system
e Sending and receiving fax
2
bull Accessing Company database
bull Submit customer order
bull On-line information service
bull accessing Internet-surfing into Netscape
bull terminal mode- billinwregistration
The network ofData2Go by Celcomtradeas shown shy
Figure Ib Celcomtrade Data2Go Network 14 I
Software uses for this type ofnetwork are
bull Delrina WinFaxPro
bull Microsoft Mail
bull Netscape
bull Lotus Notes
13 The purpose of this paper
The main purpose of this project is to develop a useable technique that suitable for
sending data wireless via RS232 communication port The system component will consist
of a desktop computer that act as input device a standard RS232 interface a transceiver
for transmit and receive signal and a modify laser poniter The suggested system will be
3
set and tested in a point-to-point configuration As the figure show below the network
diagram stated shy
J -~HJj----tcooo ~ IEco~codl---=RS=232=--_~ Personal computer Signal RS232 Laser Transceiver RS2321aser Transceiver Personal computer
Figure lc The Simples point to point data communication via RS131laser transceiver
4
Cbapter2
RS-232 INTERFACE AND SERIAL COMMUNICATION
20 Overview
RS 232 Interface in a simple universal well knows data interface RS means
Recommended Standard1 The female connector attaches to Data Communication
Equipment and male connector attaches to Data Terminal Equipment Mostly today PCs
are equipped with two RS232 ports via COMI or COM2 The additional COM port
COM3 and COM4 required additional card
RS-232 defines 25-pin communication line Every line has their own function to
accessing data The configurations ofevery pin layout are show in figure 2a
Normally The ground signal refers to pin 7 Two computers can communicate by using a
null modem A null modem is a special made direct cable and connector It is functioning
like a modem but has limited transmission range Figure 2b illustrated the common
method to wiring a null modem Pin2 and pin3 are wire together and all the cables are
connect in such a way a modem simulated between two computers
The electrical characteristic define by RS232 as
(a) Total capacitance not less than 2500 pF
(b) (b) A binary high logic output lines is + 5to + 15 volts input lines is from +3
to + 15 volts
(c) A binary low logic output lines is from -5 to -15 volts input lines is from -3
to -15 volts
(d) output lines voltages -5 and +5 -3 and +3 volts for input lines are undefined
5
Shelld~ Secondary
tntnsmltted data Transmlttins
Signal element timlne (DCEoTE)
Secondary
Relcetver received data
Signal tlmlne(DCEoTE) Looak
Loopok Secondary
Request To8end
DTERudy
Rem_ Loopb8ok amp Signal Qua
Decmlctor RinS indicator
l reg
Transmitted Data
Request to Send
DCEReady
Rivedline 818nal Detector
Reserved (Testing)
Secondary Received Lne Signel Detector
Recetve Data
reg
Crto8ent
Signal Ground Comman RetUrn
reg Rrved (Testing)
Datas18nal
I 10
rate ct UnusedTnulSmitter signal Signed
element -f
timing (DTE-DCE) bull Tnt Mode 8eooundary~ 13 c
To8ent~
Figure 2a The RS232 pin configuration [81
Pin Number Line Line Pin Number
2 m m 2
3 RD RD 3
4 RTS RTS 4
5 CTS CTS 5
6 DSR---- DSR 6
7 Common 7
8 DCD DCD 8
20 DTR DTR 20
22 R1 R1 22
Figure 2b A Null Modem Configuration [8]
6
21 The Explanation For RS1Jl Pin Abbreviation
Hence is the detail ofeach line in DB9 and DB25 function
Clear to Send (CTS)
Data Carrier Detect (OCR)
Data Set Ready (DSR)
Data Terminal Ready (DTR)
Receive Data (RO)
Ring Indicator (RI)
Requested to Send (RTS)
Transmit Data (TD)
asserted (logic state 1) by DCE it is ready to receive data
logic state 1 whenever there is data link in progress
logic state 1 when DCE is ready to communicated withDTE
logic state 1 when DTE is ready to communicated withDCE
use by DCE to send data to DTE
logic 1 by DCE when a ring is detect
logic state 1 by DTE when it want to transmit data toDCE
Use by DTE to send data to DCE
Figure lc The Detail Explanation of Abbreviation [ 8]
22 UART
UART Universal Asynchronous Receiver Transmitter is a special hardware in RS232
serial interface It sometime called as Asynchronous Communication Element
Most of the new personal computer today is equip with 16450 and 16550 UART The
function ofUART chip is to convert the parallel data to a serial data format that enable a
serial communication between two computers The UART chip also uses to convert back
7
the serial bits to parallel bits format The operation of UART mostly control by one or
more register The process of read writes data to register are through input and output
ports Figure ld showing the address of a UART for COMI and COM4
The UART have FIFO or First in First out buffer FIFO bring the meaning as the first
data to enter the buffer are first to leave The function of buffer is to hold data temporary
before it was feed to the transmission medium The modem 16550A UART have16 bytes
FIFO This means 16 bytes can be writes to UART before anything was overwrite The
16550 UART was necessary for a high-speed communication under windows or
application running under window environment
Serial port Base Register Port Address
COM 1 3F8H COM2 2F8H COM3 3E8H COM3 2E8H
Figure ld The Serial Port Base Register Port [7 ]
23 Serial Communication
Serial communication is transmission of data over a serial interface one data bit at a time
In other word data are transfer through and forth over a single wire Therefore serial
communication is more cost effective than parallel communication RS232 is an example
for serial communication interface
24 Parallel Interface
Parallel communication is a way to sending more than one data at a time (normally eight
data bits) over to a parallel device or a Com Port For an example a computer will send
eight data bits of information to a parallel printer A very simple diagram of parallel
communication was present as Figure 2e The parallel interfaces require separated wire
8
------_------------__shyp
for sending separated data and therefor allowed faster and efficient data transmission On
the other hand to setting up a parallel communication network will be more costly than
serial communication network
1 Printer Interface
1 3 4 5 6 7 8
1 Computer Interface
2 3 4 5 6 7 8
Figure 2e A parallel Printer to Computer Interface [7 ]
25 Asynchronous and synchronous data
For two devices to communicate a way of synchronizing data must be set There are two
way ofdata formatting by using either asynchronous or synchronous
The synchronous operation is such a way that for each line data transmit it has a
separated clock to synchronous that data on a time of period For example data are
transfer once in each direction to and from the computer The synchronous data format
was show in figure 2f
While the asynchronous data is such a way that data are synchronous without clock
Each time the data are transmitting the receiver need to figure out how fast the data is
running The frame of asynchronous data has start and stops bit In another world the
frame always added with additional start and stop bit The asynchronous data format was
show in figure 2g
9
01100011100 o 1 1 1 11 0 0 0 0 001 0110 1 1 0
Unique Code
Continuous Block
Direction offlow
Figure 2f Synchronous data format I 8 ]
Start Stop d7 d6 d5 d4 d3 d2 dl dO Start
1 0 1 0 1 1 0 0I 1 I IMSB LSB
Start bit Stop bit1 Data-bits 1 I
r space mark mark space mark space mark mark space space
Serial Communication
Figure 2g Asynchronous Data Format Adopted form [8]
26 The Start Parity and Stop bits
For two machines to communicate to each other first thing both machines must agree on
the rate of speed for data transfer Second thing is the data must fonnatted for
synchronous or asynchronous operation Therefor for asynchronous operation the data
fonnatted in such a way that contains start and stop bit
271 Start bit
10
The TD line at interface device (Pin3) will go high when no data been transmit To start
transmit a data Transmit serial device will set TD line to low by means ofa start bit The
synchronous operation of DCE is waiting the TD line sign change from high bit to low
bit than DCE pauses half of a bit time and start sampling the incoming data until all the
character has been completely transmit To maintain synchronimtion DCE always
sampling the incoming data string at middle ofeach bit
272 Data bits
The data bits are the bits that contain character Nonnallyone character contains eight
bits Hence is the data bits showing character Amiddot 4tH
l start bit 41----shy Data bits j
shy
I t I Io 0 0 0 0 0
1 1deg1 1
Figure 2h The Data bits Format ( 7 ]
273 Parity bits
Four basic fonns ofparity bits are NONE EVEN ODD MARK and SPACE NONE use
for transmits a character without parity bit EVEN parity use to indicate by send logic 1
after a character if there is an odd number of logic 1 bit after a character data bit
Otherwise logic for EVEN parity goes to zero Odd parity will indicate by sending logic
1 after a data of a character bits if there is an even number of logic 1 after a characters
data bits Otherwise logic for ODD parity goes to zero Mark is logic 1 parity bit after a
data character and SPACE is logic zero after the data character
11
274 Stop bits
The stop bit indicated the end of a character The serial device was always send logic 1
for stop bit
28 Data Transmit and Receive Process
281 Transmit of a character
Several steps take before characters are transmitting from processor to modem
For an example communication between processor and 8251A USART
First the processor configures UART according to the communication protocol
Second an instruction was send to UART and set the flag TxEN Next The processor
was send the character to the data buffer ofUART Then this data buffer transfer the
character to transmit buffer for preparation for transmission Once data buffer was
complete transfer the character and ready to receive a new character the TXRDY flag
will set When processor automatically write in data buffer TXRDY flag automatically
reset
Next RTS (Ready to Send)pin output pin ofUART will alerted by modem that the bits
are about to transmit RTS pin for UART is tie together with modem RTS pin while the
modem realizes about to receive character from UART CTS pin will activated Then the
character was automatically transfer to modem The internal flag TxEMPTY will set
once the character was completely transmit from UART to modem
282 Receive of a character
The process of data receiving was also take several sequence First processor configures
UART according to standard protocol Then to receive a character the processor sends a
12
p
instruction to activated the RxE flag Next DART need to be alerted about the data going
to be transmitted DSR (Data Set Ready) will activated DSR pin of DART and modem
are tied together therefore when processor read this flags and realizes that the modem
has characters to be transmitted to DART Once DSR signal been set processor set DTR
(data terminal ready) to high And once DTR pin is asserted characters was
automatically transfer out from modem Once the characters is receive by DART it
formatted the data according to their start stop parity bits The RxRDY activated when a
character was completely receive
The bock diagram ofDART was show in ftgUre 2i
transmittedT~_B_r ~Mode Register
Transmit Register-~ I I data
I [_~~~J lt-~--r I
Receiver Register L~~~l-~~mmg =71 -_Rece~~I_v-e_r-B_-un_e=r=_-_ ~_romL--_
Devices and bullControl LogiC
l Internal Transmitter I Bus c-- ~ Clocking
--_______________rece_i_ve_r__lt=__-T Circuitary
Figure 2i USART Bloek Diagram [8 ]
28 COM Port setting
COM Port is the port that allowed computer to communicated with other device
such as modem or printer The standard personal computer normally has four
communications port COM 1 and COM 2 are assign for external port All the
13
bull Accessing Company database
bull Submit customer order
bull On-line information service
bull accessing Internet-surfing into Netscape
bull terminal mode- billinwregistration
The network ofData2Go by Celcomtradeas shown shy
Figure Ib Celcomtrade Data2Go Network 14 I
Software uses for this type ofnetwork are
bull Delrina WinFaxPro
bull Microsoft Mail
bull Netscape
bull Lotus Notes
13 The purpose of this paper
The main purpose of this project is to develop a useable technique that suitable for
sending data wireless via RS232 communication port The system component will consist
of a desktop computer that act as input device a standard RS232 interface a transceiver
for transmit and receive signal and a modify laser poniter The suggested system will be
3
set and tested in a point-to-point configuration As the figure show below the network
diagram stated shy
J -~HJj----tcooo ~ IEco~codl---=RS=232=--_~ Personal computer Signal RS232 Laser Transceiver RS2321aser Transceiver Personal computer
Figure lc The Simples point to point data communication via RS131laser transceiver
4
Cbapter2
RS-232 INTERFACE AND SERIAL COMMUNICATION
20 Overview
RS 232 Interface in a simple universal well knows data interface RS means
Recommended Standard1 The female connector attaches to Data Communication
Equipment and male connector attaches to Data Terminal Equipment Mostly today PCs
are equipped with two RS232 ports via COMI or COM2 The additional COM port
COM3 and COM4 required additional card
RS-232 defines 25-pin communication line Every line has their own function to
accessing data The configurations ofevery pin layout are show in figure 2a
Normally The ground signal refers to pin 7 Two computers can communicate by using a
null modem A null modem is a special made direct cable and connector It is functioning
like a modem but has limited transmission range Figure 2b illustrated the common
method to wiring a null modem Pin2 and pin3 are wire together and all the cables are
connect in such a way a modem simulated between two computers
The electrical characteristic define by RS232 as
(a) Total capacitance not less than 2500 pF
(b) (b) A binary high logic output lines is + 5to + 15 volts input lines is from +3
to + 15 volts
(c) A binary low logic output lines is from -5 to -15 volts input lines is from -3
to -15 volts
(d) output lines voltages -5 and +5 -3 and +3 volts for input lines are undefined
5
Shelld~ Secondary
tntnsmltted data Transmlttins
Signal element timlne (DCEoTE)
Secondary
Relcetver received data
Signal tlmlne(DCEoTE) Looak
Loopok Secondary
Request To8end
DTERudy
Rem_ Loopb8ok amp Signal Qua
Decmlctor RinS indicator
l reg
Transmitted Data
Request to Send
DCEReady
Rivedline 818nal Detector
Reserved (Testing)
Secondary Received Lne Signel Detector
Recetve Data
reg
Crto8ent
Signal Ground Comman RetUrn
reg Rrved (Testing)
Datas18nal
I 10
rate ct UnusedTnulSmitter signal Signed
element -f
timing (DTE-DCE) bull Tnt Mode 8eooundary~ 13 c
To8ent~
Figure 2a The RS232 pin configuration [81
Pin Number Line Line Pin Number
2 m m 2
3 RD RD 3
4 RTS RTS 4
5 CTS CTS 5
6 DSR---- DSR 6
7 Common 7
8 DCD DCD 8
20 DTR DTR 20
22 R1 R1 22
Figure 2b A Null Modem Configuration [8]
6
21 The Explanation For RS1Jl Pin Abbreviation
Hence is the detail ofeach line in DB9 and DB25 function
Clear to Send (CTS)
Data Carrier Detect (OCR)
Data Set Ready (DSR)
Data Terminal Ready (DTR)
Receive Data (RO)
Ring Indicator (RI)
Requested to Send (RTS)
Transmit Data (TD)
asserted (logic state 1) by DCE it is ready to receive data
logic state 1 whenever there is data link in progress
logic state 1 when DCE is ready to communicated withDTE
logic state 1 when DTE is ready to communicated withDCE
use by DCE to send data to DTE
logic 1 by DCE when a ring is detect
logic state 1 by DTE when it want to transmit data toDCE
Use by DTE to send data to DCE
Figure lc The Detail Explanation of Abbreviation [ 8]
22 UART
UART Universal Asynchronous Receiver Transmitter is a special hardware in RS232
serial interface It sometime called as Asynchronous Communication Element
Most of the new personal computer today is equip with 16450 and 16550 UART The
function ofUART chip is to convert the parallel data to a serial data format that enable a
serial communication between two computers The UART chip also uses to convert back
7
the serial bits to parallel bits format The operation of UART mostly control by one or
more register The process of read writes data to register are through input and output
ports Figure ld showing the address of a UART for COMI and COM4
The UART have FIFO or First in First out buffer FIFO bring the meaning as the first
data to enter the buffer are first to leave The function of buffer is to hold data temporary
before it was feed to the transmission medium The modem 16550A UART have16 bytes
FIFO This means 16 bytes can be writes to UART before anything was overwrite The
16550 UART was necessary for a high-speed communication under windows or
application running under window environment
Serial port Base Register Port Address
COM 1 3F8H COM2 2F8H COM3 3E8H COM3 2E8H
Figure ld The Serial Port Base Register Port [7 ]
23 Serial Communication
Serial communication is transmission of data over a serial interface one data bit at a time
In other word data are transfer through and forth over a single wire Therefore serial
communication is more cost effective than parallel communication RS232 is an example
for serial communication interface
24 Parallel Interface
Parallel communication is a way to sending more than one data at a time (normally eight
data bits) over to a parallel device or a Com Port For an example a computer will send
eight data bits of information to a parallel printer A very simple diagram of parallel
communication was present as Figure 2e The parallel interfaces require separated wire
8
------_------------__shyp
for sending separated data and therefor allowed faster and efficient data transmission On
the other hand to setting up a parallel communication network will be more costly than
serial communication network
1 Printer Interface
1 3 4 5 6 7 8
1 Computer Interface
2 3 4 5 6 7 8
Figure 2e A parallel Printer to Computer Interface [7 ]
25 Asynchronous and synchronous data
For two devices to communicate a way of synchronizing data must be set There are two
way ofdata formatting by using either asynchronous or synchronous
The synchronous operation is such a way that for each line data transmit it has a
separated clock to synchronous that data on a time of period For example data are
transfer once in each direction to and from the computer The synchronous data format
was show in figure 2f
While the asynchronous data is such a way that data are synchronous without clock
Each time the data are transmitting the receiver need to figure out how fast the data is
running The frame of asynchronous data has start and stops bit In another world the
frame always added with additional start and stop bit The asynchronous data format was
show in figure 2g
9
01100011100 o 1 1 1 11 0 0 0 0 001 0110 1 1 0
Unique Code
Continuous Block
Direction offlow
Figure 2f Synchronous data format I 8 ]
Start Stop d7 d6 d5 d4 d3 d2 dl dO Start
1 0 1 0 1 1 0 0I 1 I IMSB LSB
Start bit Stop bit1 Data-bits 1 I
r space mark mark space mark space mark mark space space
Serial Communication
Figure 2g Asynchronous Data Format Adopted form [8]
26 The Start Parity and Stop bits
For two machines to communicate to each other first thing both machines must agree on
the rate of speed for data transfer Second thing is the data must fonnatted for
synchronous or asynchronous operation Therefor for asynchronous operation the data
fonnatted in such a way that contains start and stop bit
271 Start bit
10
The TD line at interface device (Pin3) will go high when no data been transmit To start
transmit a data Transmit serial device will set TD line to low by means ofa start bit The
synchronous operation of DCE is waiting the TD line sign change from high bit to low
bit than DCE pauses half of a bit time and start sampling the incoming data until all the
character has been completely transmit To maintain synchronimtion DCE always
sampling the incoming data string at middle ofeach bit
272 Data bits
The data bits are the bits that contain character Nonnallyone character contains eight
bits Hence is the data bits showing character Amiddot 4tH
l start bit 41----shy Data bits j
shy
I t I Io 0 0 0 0 0
1 1deg1 1
Figure 2h The Data bits Format ( 7 ]
273 Parity bits
Four basic fonns ofparity bits are NONE EVEN ODD MARK and SPACE NONE use
for transmits a character without parity bit EVEN parity use to indicate by send logic 1
after a character if there is an odd number of logic 1 bit after a character data bit
Otherwise logic for EVEN parity goes to zero Odd parity will indicate by sending logic
1 after a data of a character bits if there is an even number of logic 1 after a characters
data bits Otherwise logic for ODD parity goes to zero Mark is logic 1 parity bit after a
data character and SPACE is logic zero after the data character
11
274 Stop bits
The stop bit indicated the end of a character The serial device was always send logic 1
for stop bit
28 Data Transmit and Receive Process
281 Transmit of a character
Several steps take before characters are transmitting from processor to modem
For an example communication between processor and 8251A USART
First the processor configures UART according to the communication protocol
Second an instruction was send to UART and set the flag TxEN Next The processor
was send the character to the data buffer ofUART Then this data buffer transfer the
character to transmit buffer for preparation for transmission Once data buffer was
complete transfer the character and ready to receive a new character the TXRDY flag
will set When processor automatically write in data buffer TXRDY flag automatically
reset
Next RTS (Ready to Send)pin output pin ofUART will alerted by modem that the bits
are about to transmit RTS pin for UART is tie together with modem RTS pin while the
modem realizes about to receive character from UART CTS pin will activated Then the
character was automatically transfer to modem The internal flag TxEMPTY will set
once the character was completely transmit from UART to modem
282 Receive of a character
The process of data receiving was also take several sequence First processor configures
UART according to standard protocol Then to receive a character the processor sends a
12
p
instruction to activated the RxE flag Next DART need to be alerted about the data going
to be transmitted DSR (Data Set Ready) will activated DSR pin of DART and modem
are tied together therefore when processor read this flags and realizes that the modem
has characters to be transmitted to DART Once DSR signal been set processor set DTR
(data terminal ready) to high And once DTR pin is asserted characters was
automatically transfer out from modem Once the characters is receive by DART it
formatted the data according to their start stop parity bits The RxRDY activated when a
character was completely receive
The bock diagram ofDART was show in ftgUre 2i
transmittedT~_B_r ~Mode Register
Transmit Register-~ I I data
I [_~~~J lt-~--r I
Receiver Register L~~~l-~~mmg =71 -_Rece~~I_v-e_r-B_-un_e=r=_-_ ~_romL--_
Devices and bullControl LogiC
l Internal Transmitter I Bus c-- ~ Clocking
--_______________rece_i_ve_r__lt=__-T Circuitary
Figure 2i USART Bloek Diagram [8 ]
28 COM Port setting
COM Port is the port that allowed computer to communicated with other device
such as modem or printer The standard personal computer normally has four
communications port COM 1 and COM 2 are assign for external port All the
13
set and tested in a point-to-point configuration As the figure show below the network
diagram stated shy
J -~HJj----tcooo ~ IEco~codl---=RS=232=--_~ Personal computer Signal RS232 Laser Transceiver RS2321aser Transceiver Personal computer
Figure lc The Simples point to point data communication via RS131laser transceiver
4
Cbapter2
RS-232 INTERFACE AND SERIAL COMMUNICATION
20 Overview
RS 232 Interface in a simple universal well knows data interface RS means
Recommended Standard1 The female connector attaches to Data Communication
Equipment and male connector attaches to Data Terminal Equipment Mostly today PCs
are equipped with two RS232 ports via COMI or COM2 The additional COM port
COM3 and COM4 required additional card
RS-232 defines 25-pin communication line Every line has their own function to
accessing data The configurations ofevery pin layout are show in figure 2a
Normally The ground signal refers to pin 7 Two computers can communicate by using a
null modem A null modem is a special made direct cable and connector It is functioning
like a modem but has limited transmission range Figure 2b illustrated the common
method to wiring a null modem Pin2 and pin3 are wire together and all the cables are
connect in such a way a modem simulated between two computers
The electrical characteristic define by RS232 as
(a) Total capacitance not less than 2500 pF
(b) (b) A binary high logic output lines is + 5to + 15 volts input lines is from +3
to + 15 volts
(c) A binary low logic output lines is from -5 to -15 volts input lines is from -3
to -15 volts
(d) output lines voltages -5 and +5 -3 and +3 volts for input lines are undefined
5
Shelld~ Secondary
tntnsmltted data Transmlttins
Signal element timlne (DCEoTE)
Secondary
Relcetver received data
Signal tlmlne(DCEoTE) Looak
Loopok Secondary
Request To8end
DTERudy
Rem_ Loopb8ok amp Signal Qua
Decmlctor RinS indicator
l reg
Transmitted Data
Request to Send
DCEReady
Rivedline 818nal Detector
Reserved (Testing)
Secondary Received Lne Signel Detector
Recetve Data
reg
Crto8ent
Signal Ground Comman RetUrn
reg Rrved (Testing)
Datas18nal
I 10
rate ct UnusedTnulSmitter signal Signed
element -f
timing (DTE-DCE) bull Tnt Mode 8eooundary~ 13 c
To8ent~
Figure 2a The RS232 pin configuration [81
Pin Number Line Line Pin Number
2 m m 2
3 RD RD 3
4 RTS RTS 4
5 CTS CTS 5
6 DSR---- DSR 6
7 Common 7
8 DCD DCD 8
20 DTR DTR 20
22 R1 R1 22
Figure 2b A Null Modem Configuration [8]
6
21 The Explanation For RS1Jl Pin Abbreviation
Hence is the detail ofeach line in DB9 and DB25 function
Clear to Send (CTS)
Data Carrier Detect (OCR)
Data Set Ready (DSR)
Data Terminal Ready (DTR)
Receive Data (RO)
Ring Indicator (RI)
Requested to Send (RTS)
Transmit Data (TD)
asserted (logic state 1) by DCE it is ready to receive data
logic state 1 whenever there is data link in progress
logic state 1 when DCE is ready to communicated withDTE
logic state 1 when DTE is ready to communicated withDCE
use by DCE to send data to DTE
logic 1 by DCE when a ring is detect
logic state 1 by DTE when it want to transmit data toDCE
Use by DTE to send data to DCE
Figure lc The Detail Explanation of Abbreviation [ 8]
22 UART
UART Universal Asynchronous Receiver Transmitter is a special hardware in RS232
serial interface It sometime called as Asynchronous Communication Element
Most of the new personal computer today is equip with 16450 and 16550 UART The
function ofUART chip is to convert the parallel data to a serial data format that enable a
serial communication between two computers The UART chip also uses to convert back
7
the serial bits to parallel bits format The operation of UART mostly control by one or
more register The process of read writes data to register are through input and output
ports Figure ld showing the address of a UART for COMI and COM4
The UART have FIFO or First in First out buffer FIFO bring the meaning as the first
data to enter the buffer are first to leave The function of buffer is to hold data temporary
before it was feed to the transmission medium The modem 16550A UART have16 bytes
FIFO This means 16 bytes can be writes to UART before anything was overwrite The
16550 UART was necessary for a high-speed communication under windows or
application running under window environment
Serial port Base Register Port Address
COM 1 3F8H COM2 2F8H COM3 3E8H COM3 2E8H
Figure ld The Serial Port Base Register Port [7 ]
23 Serial Communication
Serial communication is transmission of data over a serial interface one data bit at a time
In other word data are transfer through and forth over a single wire Therefore serial
communication is more cost effective than parallel communication RS232 is an example
for serial communication interface
24 Parallel Interface
Parallel communication is a way to sending more than one data at a time (normally eight
data bits) over to a parallel device or a Com Port For an example a computer will send
eight data bits of information to a parallel printer A very simple diagram of parallel
communication was present as Figure 2e The parallel interfaces require separated wire
8
------_------------__shyp
for sending separated data and therefor allowed faster and efficient data transmission On
the other hand to setting up a parallel communication network will be more costly than
serial communication network
1 Printer Interface
1 3 4 5 6 7 8
1 Computer Interface
2 3 4 5 6 7 8
Figure 2e A parallel Printer to Computer Interface [7 ]
25 Asynchronous and synchronous data
For two devices to communicate a way of synchronizing data must be set There are two
way ofdata formatting by using either asynchronous or synchronous
The synchronous operation is such a way that for each line data transmit it has a
separated clock to synchronous that data on a time of period For example data are
transfer once in each direction to and from the computer The synchronous data format
was show in figure 2f
While the asynchronous data is such a way that data are synchronous without clock
Each time the data are transmitting the receiver need to figure out how fast the data is
running The frame of asynchronous data has start and stops bit In another world the
frame always added with additional start and stop bit The asynchronous data format was
show in figure 2g
9
01100011100 o 1 1 1 11 0 0 0 0 001 0110 1 1 0
Unique Code
Continuous Block
Direction offlow
Figure 2f Synchronous data format I 8 ]
Start Stop d7 d6 d5 d4 d3 d2 dl dO Start
1 0 1 0 1 1 0 0I 1 I IMSB LSB
Start bit Stop bit1 Data-bits 1 I
r space mark mark space mark space mark mark space space
Serial Communication
Figure 2g Asynchronous Data Format Adopted form [8]
26 The Start Parity and Stop bits
For two machines to communicate to each other first thing both machines must agree on
the rate of speed for data transfer Second thing is the data must fonnatted for
synchronous or asynchronous operation Therefor for asynchronous operation the data
fonnatted in such a way that contains start and stop bit
271 Start bit
10
The TD line at interface device (Pin3) will go high when no data been transmit To start
transmit a data Transmit serial device will set TD line to low by means ofa start bit The
synchronous operation of DCE is waiting the TD line sign change from high bit to low
bit than DCE pauses half of a bit time and start sampling the incoming data until all the
character has been completely transmit To maintain synchronimtion DCE always
sampling the incoming data string at middle ofeach bit
272 Data bits
The data bits are the bits that contain character Nonnallyone character contains eight
bits Hence is the data bits showing character Amiddot 4tH
l start bit 41----shy Data bits j
shy
I t I Io 0 0 0 0 0
1 1deg1 1
Figure 2h The Data bits Format ( 7 ]
273 Parity bits
Four basic fonns ofparity bits are NONE EVEN ODD MARK and SPACE NONE use
for transmits a character without parity bit EVEN parity use to indicate by send logic 1
after a character if there is an odd number of logic 1 bit after a character data bit
Otherwise logic for EVEN parity goes to zero Odd parity will indicate by sending logic
1 after a data of a character bits if there is an even number of logic 1 after a characters
data bits Otherwise logic for ODD parity goes to zero Mark is logic 1 parity bit after a
data character and SPACE is logic zero after the data character
11
274 Stop bits
The stop bit indicated the end of a character The serial device was always send logic 1
for stop bit
28 Data Transmit and Receive Process
281 Transmit of a character
Several steps take before characters are transmitting from processor to modem
For an example communication between processor and 8251A USART
First the processor configures UART according to the communication protocol
Second an instruction was send to UART and set the flag TxEN Next The processor
was send the character to the data buffer ofUART Then this data buffer transfer the
character to transmit buffer for preparation for transmission Once data buffer was
complete transfer the character and ready to receive a new character the TXRDY flag
will set When processor automatically write in data buffer TXRDY flag automatically
reset
Next RTS (Ready to Send)pin output pin ofUART will alerted by modem that the bits
are about to transmit RTS pin for UART is tie together with modem RTS pin while the
modem realizes about to receive character from UART CTS pin will activated Then the
character was automatically transfer to modem The internal flag TxEMPTY will set
once the character was completely transmit from UART to modem
282 Receive of a character
The process of data receiving was also take several sequence First processor configures
UART according to standard protocol Then to receive a character the processor sends a
12
p
instruction to activated the RxE flag Next DART need to be alerted about the data going
to be transmitted DSR (Data Set Ready) will activated DSR pin of DART and modem
are tied together therefore when processor read this flags and realizes that the modem
has characters to be transmitted to DART Once DSR signal been set processor set DTR
(data terminal ready) to high And once DTR pin is asserted characters was
automatically transfer out from modem Once the characters is receive by DART it
formatted the data according to their start stop parity bits The RxRDY activated when a
character was completely receive
The bock diagram ofDART was show in ftgUre 2i
transmittedT~_B_r ~Mode Register
Transmit Register-~ I I data
I [_~~~J lt-~--r I
Receiver Register L~~~l-~~mmg =71 -_Rece~~I_v-e_r-B_-un_e=r=_-_ ~_romL--_
Devices and bullControl LogiC
l Internal Transmitter I Bus c-- ~ Clocking
--_______________rece_i_ve_r__lt=__-T Circuitary
Figure 2i USART Bloek Diagram [8 ]
28 COM Port setting
COM Port is the port that allowed computer to communicated with other device
such as modem or printer The standard personal computer normally has four
communications port COM 1 and COM 2 are assign for external port All the
13
Cbapter2
RS-232 INTERFACE AND SERIAL COMMUNICATION
20 Overview
RS 232 Interface in a simple universal well knows data interface RS means
Recommended Standard1 The female connector attaches to Data Communication
Equipment and male connector attaches to Data Terminal Equipment Mostly today PCs
are equipped with two RS232 ports via COMI or COM2 The additional COM port
COM3 and COM4 required additional card
RS-232 defines 25-pin communication line Every line has their own function to
accessing data The configurations ofevery pin layout are show in figure 2a
Normally The ground signal refers to pin 7 Two computers can communicate by using a
null modem A null modem is a special made direct cable and connector It is functioning
like a modem but has limited transmission range Figure 2b illustrated the common
method to wiring a null modem Pin2 and pin3 are wire together and all the cables are
connect in such a way a modem simulated between two computers
The electrical characteristic define by RS232 as
(a) Total capacitance not less than 2500 pF
(b) (b) A binary high logic output lines is + 5to + 15 volts input lines is from +3
to + 15 volts
(c) A binary low logic output lines is from -5 to -15 volts input lines is from -3
to -15 volts
(d) output lines voltages -5 and +5 -3 and +3 volts for input lines are undefined
5
Shelld~ Secondary
tntnsmltted data Transmlttins
Signal element timlne (DCEoTE)
Secondary
Relcetver received data
Signal tlmlne(DCEoTE) Looak
Loopok Secondary
Request To8end
DTERudy
Rem_ Loopb8ok amp Signal Qua
Decmlctor RinS indicator
l reg
Transmitted Data
Request to Send
DCEReady
Rivedline 818nal Detector
Reserved (Testing)
Secondary Received Lne Signel Detector
Recetve Data
reg
Crto8ent
Signal Ground Comman RetUrn
reg Rrved (Testing)
Datas18nal
I 10
rate ct UnusedTnulSmitter signal Signed
element -f
timing (DTE-DCE) bull Tnt Mode 8eooundary~ 13 c
To8ent~
Figure 2a The RS232 pin configuration [81
Pin Number Line Line Pin Number
2 m m 2
3 RD RD 3
4 RTS RTS 4
5 CTS CTS 5
6 DSR---- DSR 6
7 Common 7
8 DCD DCD 8
20 DTR DTR 20
22 R1 R1 22
Figure 2b A Null Modem Configuration [8]
6
21 The Explanation For RS1Jl Pin Abbreviation
Hence is the detail ofeach line in DB9 and DB25 function
Clear to Send (CTS)
Data Carrier Detect (OCR)
Data Set Ready (DSR)
Data Terminal Ready (DTR)
Receive Data (RO)
Ring Indicator (RI)
Requested to Send (RTS)
Transmit Data (TD)
asserted (logic state 1) by DCE it is ready to receive data
logic state 1 whenever there is data link in progress
logic state 1 when DCE is ready to communicated withDTE
logic state 1 when DTE is ready to communicated withDCE
use by DCE to send data to DTE
logic 1 by DCE when a ring is detect
logic state 1 by DTE when it want to transmit data toDCE
Use by DTE to send data to DCE
Figure lc The Detail Explanation of Abbreviation [ 8]
22 UART
UART Universal Asynchronous Receiver Transmitter is a special hardware in RS232
serial interface It sometime called as Asynchronous Communication Element
Most of the new personal computer today is equip with 16450 and 16550 UART The
function ofUART chip is to convert the parallel data to a serial data format that enable a
serial communication between two computers The UART chip also uses to convert back
7
the serial bits to parallel bits format The operation of UART mostly control by one or
more register The process of read writes data to register are through input and output
ports Figure ld showing the address of a UART for COMI and COM4
The UART have FIFO or First in First out buffer FIFO bring the meaning as the first
data to enter the buffer are first to leave The function of buffer is to hold data temporary
before it was feed to the transmission medium The modem 16550A UART have16 bytes
FIFO This means 16 bytes can be writes to UART before anything was overwrite The
16550 UART was necessary for a high-speed communication under windows or
application running under window environment
Serial port Base Register Port Address
COM 1 3F8H COM2 2F8H COM3 3E8H COM3 2E8H
Figure ld The Serial Port Base Register Port [7 ]
23 Serial Communication
Serial communication is transmission of data over a serial interface one data bit at a time
In other word data are transfer through and forth over a single wire Therefore serial
communication is more cost effective than parallel communication RS232 is an example
for serial communication interface
24 Parallel Interface
Parallel communication is a way to sending more than one data at a time (normally eight
data bits) over to a parallel device or a Com Port For an example a computer will send
eight data bits of information to a parallel printer A very simple diagram of parallel
communication was present as Figure 2e The parallel interfaces require separated wire
8
------_------------__shyp
for sending separated data and therefor allowed faster and efficient data transmission On
the other hand to setting up a parallel communication network will be more costly than
serial communication network
1 Printer Interface
1 3 4 5 6 7 8
1 Computer Interface
2 3 4 5 6 7 8
Figure 2e A parallel Printer to Computer Interface [7 ]
25 Asynchronous and synchronous data
For two devices to communicate a way of synchronizing data must be set There are two
way ofdata formatting by using either asynchronous or synchronous
The synchronous operation is such a way that for each line data transmit it has a
separated clock to synchronous that data on a time of period For example data are
transfer once in each direction to and from the computer The synchronous data format
was show in figure 2f
While the asynchronous data is such a way that data are synchronous without clock
Each time the data are transmitting the receiver need to figure out how fast the data is
running The frame of asynchronous data has start and stops bit In another world the
frame always added with additional start and stop bit The asynchronous data format was
show in figure 2g
9
01100011100 o 1 1 1 11 0 0 0 0 001 0110 1 1 0
Unique Code
Continuous Block
Direction offlow
Figure 2f Synchronous data format I 8 ]
Start Stop d7 d6 d5 d4 d3 d2 dl dO Start
1 0 1 0 1 1 0 0I 1 I IMSB LSB
Start bit Stop bit1 Data-bits 1 I
r space mark mark space mark space mark mark space space
Serial Communication
Figure 2g Asynchronous Data Format Adopted form [8]
26 The Start Parity and Stop bits
For two machines to communicate to each other first thing both machines must agree on
the rate of speed for data transfer Second thing is the data must fonnatted for
synchronous or asynchronous operation Therefor for asynchronous operation the data
fonnatted in such a way that contains start and stop bit
271 Start bit
10
The TD line at interface device (Pin3) will go high when no data been transmit To start
transmit a data Transmit serial device will set TD line to low by means ofa start bit The
synchronous operation of DCE is waiting the TD line sign change from high bit to low
bit than DCE pauses half of a bit time and start sampling the incoming data until all the
character has been completely transmit To maintain synchronimtion DCE always
sampling the incoming data string at middle ofeach bit
272 Data bits
The data bits are the bits that contain character Nonnallyone character contains eight
bits Hence is the data bits showing character Amiddot 4tH
l start bit 41----shy Data bits j
shy
I t I Io 0 0 0 0 0
1 1deg1 1
Figure 2h The Data bits Format ( 7 ]
273 Parity bits
Four basic fonns ofparity bits are NONE EVEN ODD MARK and SPACE NONE use
for transmits a character without parity bit EVEN parity use to indicate by send logic 1
after a character if there is an odd number of logic 1 bit after a character data bit
Otherwise logic for EVEN parity goes to zero Odd parity will indicate by sending logic
1 after a data of a character bits if there is an even number of logic 1 after a characters
data bits Otherwise logic for ODD parity goes to zero Mark is logic 1 parity bit after a
data character and SPACE is logic zero after the data character
11
274 Stop bits
The stop bit indicated the end of a character The serial device was always send logic 1
for stop bit
28 Data Transmit and Receive Process
281 Transmit of a character
Several steps take before characters are transmitting from processor to modem
For an example communication between processor and 8251A USART
First the processor configures UART according to the communication protocol
Second an instruction was send to UART and set the flag TxEN Next The processor
was send the character to the data buffer ofUART Then this data buffer transfer the
character to transmit buffer for preparation for transmission Once data buffer was
complete transfer the character and ready to receive a new character the TXRDY flag
will set When processor automatically write in data buffer TXRDY flag automatically
reset
Next RTS (Ready to Send)pin output pin ofUART will alerted by modem that the bits
are about to transmit RTS pin for UART is tie together with modem RTS pin while the
modem realizes about to receive character from UART CTS pin will activated Then the
character was automatically transfer to modem The internal flag TxEMPTY will set
once the character was completely transmit from UART to modem
282 Receive of a character
The process of data receiving was also take several sequence First processor configures
UART according to standard protocol Then to receive a character the processor sends a
12
p
instruction to activated the RxE flag Next DART need to be alerted about the data going
to be transmitted DSR (Data Set Ready) will activated DSR pin of DART and modem
are tied together therefore when processor read this flags and realizes that the modem
has characters to be transmitted to DART Once DSR signal been set processor set DTR
(data terminal ready) to high And once DTR pin is asserted characters was
automatically transfer out from modem Once the characters is receive by DART it
formatted the data according to their start stop parity bits The RxRDY activated when a
character was completely receive
The bock diagram ofDART was show in ftgUre 2i
transmittedT~_B_r ~Mode Register
Transmit Register-~ I I data
I [_~~~J lt-~--r I
Receiver Register L~~~l-~~mmg =71 -_Rece~~I_v-e_r-B_-un_e=r=_-_ ~_romL--_
Devices and bullControl LogiC
l Internal Transmitter I Bus c-- ~ Clocking
--_______________rece_i_ve_r__lt=__-T Circuitary
Figure 2i USART Bloek Diagram [8 ]
28 COM Port setting
COM Port is the port that allowed computer to communicated with other device
such as modem or printer The standard personal computer normally has four
communications port COM 1 and COM 2 are assign for external port All the
13
Shelld~ Secondary
tntnsmltted data Transmlttins
Signal element timlne (DCEoTE)
Secondary
Relcetver received data
Signal tlmlne(DCEoTE) Looak
Loopok Secondary
Request To8end
DTERudy
Rem_ Loopb8ok amp Signal Qua
Decmlctor RinS indicator
l reg
Transmitted Data
Request to Send
DCEReady
Rivedline 818nal Detector
Reserved (Testing)
Secondary Received Lne Signel Detector
Recetve Data
reg
Crto8ent
Signal Ground Comman RetUrn
reg Rrved (Testing)
Datas18nal
I 10
rate ct UnusedTnulSmitter signal Signed
element -f
timing (DTE-DCE) bull Tnt Mode 8eooundary~ 13 c
To8ent~
Figure 2a The RS232 pin configuration [81
Pin Number Line Line Pin Number
2 m m 2
3 RD RD 3
4 RTS RTS 4
5 CTS CTS 5
6 DSR---- DSR 6
7 Common 7
8 DCD DCD 8
20 DTR DTR 20
22 R1 R1 22
Figure 2b A Null Modem Configuration [8]
6
21 The Explanation For RS1Jl Pin Abbreviation
Hence is the detail ofeach line in DB9 and DB25 function
Clear to Send (CTS)
Data Carrier Detect (OCR)
Data Set Ready (DSR)
Data Terminal Ready (DTR)
Receive Data (RO)
Ring Indicator (RI)
Requested to Send (RTS)
Transmit Data (TD)
asserted (logic state 1) by DCE it is ready to receive data
logic state 1 whenever there is data link in progress
logic state 1 when DCE is ready to communicated withDTE
logic state 1 when DTE is ready to communicated withDCE
use by DCE to send data to DTE
logic 1 by DCE when a ring is detect
logic state 1 by DTE when it want to transmit data toDCE
Use by DTE to send data to DCE
Figure lc The Detail Explanation of Abbreviation [ 8]
22 UART
UART Universal Asynchronous Receiver Transmitter is a special hardware in RS232
serial interface It sometime called as Asynchronous Communication Element
Most of the new personal computer today is equip with 16450 and 16550 UART The
function ofUART chip is to convert the parallel data to a serial data format that enable a
serial communication between two computers The UART chip also uses to convert back
7
the serial bits to parallel bits format The operation of UART mostly control by one or
more register The process of read writes data to register are through input and output
ports Figure ld showing the address of a UART for COMI and COM4
The UART have FIFO or First in First out buffer FIFO bring the meaning as the first
data to enter the buffer are first to leave The function of buffer is to hold data temporary
before it was feed to the transmission medium The modem 16550A UART have16 bytes
FIFO This means 16 bytes can be writes to UART before anything was overwrite The
16550 UART was necessary for a high-speed communication under windows or
application running under window environment
Serial port Base Register Port Address
COM 1 3F8H COM2 2F8H COM3 3E8H COM3 2E8H
Figure ld The Serial Port Base Register Port [7 ]
23 Serial Communication
Serial communication is transmission of data over a serial interface one data bit at a time
In other word data are transfer through and forth over a single wire Therefore serial
communication is more cost effective than parallel communication RS232 is an example
for serial communication interface
24 Parallel Interface
Parallel communication is a way to sending more than one data at a time (normally eight
data bits) over to a parallel device or a Com Port For an example a computer will send
eight data bits of information to a parallel printer A very simple diagram of parallel
communication was present as Figure 2e The parallel interfaces require separated wire
8
------_------------__shyp
for sending separated data and therefor allowed faster and efficient data transmission On
the other hand to setting up a parallel communication network will be more costly than
serial communication network
1 Printer Interface
1 3 4 5 6 7 8
1 Computer Interface
2 3 4 5 6 7 8
Figure 2e A parallel Printer to Computer Interface [7 ]
25 Asynchronous and synchronous data
For two devices to communicate a way of synchronizing data must be set There are two
way ofdata formatting by using either asynchronous or synchronous
The synchronous operation is such a way that for each line data transmit it has a
separated clock to synchronous that data on a time of period For example data are
transfer once in each direction to and from the computer The synchronous data format
was show in figure 2f
While the asynchronous data is such a way that data are synchronous without clock
Each time the data are transmitting the receiver need to figure out how fast the data is
running The frame of asynchronous data has start and stops bit In another world the
frame always added with additional start and stop bit The asynchronous data format was
show in figure 2g
9
01100011100 o 1 1 1 11 0 0 0 0 001 0110 1 1 0
Unique Code
Continuous Block
Direction offlow
Figure 2f Synchronous data format I 8 ]
Start Stop d7 d6 d5 d4 d3 d2 dl dO Start
1 0 1 0 1 1 0 0I 1 I IMSB LSB
Start bit Stop bit1 Data-bits 1 I
r space mark mark space mark space mark mark space space
Serial Communication
Figure 2g Asynchronous Data Format Adopted form [8]
26 The Start Parity and Stop bits
For two machines to communicate to each other first thing both machines must agree on
the rate of speed for data transfer Second thing is the data must fonnatted for
synchronous or asynchronous operation Therefor for asynchronous operation the data
fonnatted in such a way that contains start and stop bit
271 Start bit
10
The TD line at interface device (Pin3) will go high when no data been transmit To start
transmit a data Transmit serial device will set TD line to low by means ofa start bit The
synchronous operation of DCE is waiting the TD line sign change from high bit to low
bit than DCE pauses half of a bit time and start sampling the incoming data until all the
character has been completely transmit To maintain synchronimtion DCE always
sampling the incoming data string at middle ofeach bit
272 Data bits
The data bits are the bits that contain character Nonnallyone character contains eight
bits Hence is the data bits showing character Amiddot 4tH
l start bit 41----shy Data bits j
shy
I t I Io 0 0 0 0 0
1 1deg1 1
Figure 2h The Data bits Format ( 7 ]
273 Parity bits
Four basic fonns ofparity bits are NONE EVEN ODD MARK and SPACE NONE use
for transmits a character without parity bit EVEN parity use to indicate by send logic 1
after a character if there is an odd number of logic 1 bit after a character data bit
Otherwise logic for EVEN parity goes to zero Odd parity will indicate by sending logic
1 after a data of a character bits if there is an even number of logic 1 after a characters
data bits Otherwise logic for ODD parity goes to zero Mark is logic 1 parity bit after a
data character and SPACE is logic zero after the data character
11
274 Stop bits
The stop bit indicated the end of a character The serial device was always send logic 1
for stop bit
28 Data Transmit and Receive Process
281 Transmit of a character
Several steps take before characters are transmitting from processor to modem
For an example communication between processor and 8251A USART
First the processor configures UART according to the communication protocol
Second an instruction was send to UART and set the flag TxEN Next The processor
was send the character to the data buffer ofUART Then this data buffer transfer the
character to transmit buffer for preparation for transmission Once data buffer was
complete transfer the character and ready to receive a new character the TXRDY flag
will set When processor automatically write in data buffer TXRDY flag automatically
reset
Next RTS (Ready to Send)pin output pin ofUART will alerted by modem that the bits
are about to transmit RTS pin for UART is tie together with modem RTS pin while the
modem realizes about to receive character from UART CTS pin will activated Then the
character was automatically transfer to modem The internal flag TxEMPTY will set
once the character was completely transmit from UART to modem
282 Receive of a character
The process of data receiving was also take several sequence First processor configures
UART according to standard protocol Then to receive a character the processor sends a
12
p
instruction to activated the RxE flag Next DART need to be alerted about the data going
to be transmitted DSR (Data Set Ready) will activated DSR pin of DART and modem
are tied together therefore when processor read this flags and realizes that the modem
has characters to be transmitted to DART Once DSR signal been set processor set DTR
(data terminal ready) to high And once DTR pin is asserted characters was
automatically transfer out from modem Once the characters is receive by DART it
formatted the data according to their start stop parity bits The RxRDY activated when a
character was completely receive
The bock diagram ofDART was show in ftgUre 2i
transmittedT~_B_r ~Mode Register
Transmit Register-~ I I data
I [_~~~J lt-~--r I
Receiver Register L~~~l-~~mmg =71 -_Rece~~I_v-e_r-B_-un_e=r=_-_ ~_romL--_
Devices and bullControl LogiC
l Internal Transmitter I Bus c-- ~ Clocking
--_______________rece_i_ve_r__lt=__-T Circuitary
Figure 2i USART Bloek Diagram [8 ]
28 COM Port setting
COM Port is the port that allowed computer to communicated with other device
such as modem or printer The standard personal computer normally has four
communications port COM 1 and COM 2 are assign for external port All the
13
21 The Explanation For RS1Jl Pin Abbreviation
Hence is the detail ofeach line in DB9 and DB25 function
Clear to Send (CTS)
Data Carrier Detect (OCR)
Data Set Ready (DSR)
Data Terminal Ready (DTR)
Receive Data (RO)
Ring Indicator (RI)
Requested to Send (RTS)
Transmit Data (TD)
asserted (logic state 1) by DCE it is ready to receive data
logic state 1 whenever there is data link in progress
logic state 1 when DCE is ready to communicated withDTE
logic state 1 when DTE is ready to communicated withDCE
use by DCE to send data to DTE
logic 1 by DCE when a ring is detect
logic state 1 by DTE when it want to transmit data toDCE
Use by DTE to send data to DCE
Figure lc The Detail Explanation of Abbreviation [ 8]
22 UART
UART Universal Asynchronous Receiver Transmitter is a special hardware in RS232
serial interface It sometime called as Asynchronous Communication Element
Most of the new personal computer today is equip with 16450 and 16550 UART The
function ofUART chip is to convert the parallel data to a serial data format that enable a
serial communication between two computers The UART chip also uses to convert back
7
the serial bits to parallel bits format The operation of UART mostly control by one or
more register The process of read writes data to register are through input and output
ports Figure ld showing the address of a UART for COMI and COM4
The UART have FIFO or First in First out buffer FIFO bring the meaning as the first
data to enter the buffer are first to leave The function of buffer is to hold data temporary
before it was feed to the transmission medium The modem 16550A UART have16 bytes
FIFO This means 16 bytes can be writes to UART before anything was overwrite The
16550 UART was necessary for a high-speed communication under windows or
application running under window environment
Serial port Base Register Port Address
COM 1 3F8H COM2 2F8H COM3 3E8H COM3 2E8H
Figure ld The Serial Port Base Register Port [7 ]
23 Serial Communication
Serial communication is transmission of data over a serial interface one data bit at a time
In other word data are transfer through and forth over a single wire Therefore serial
communication is more cost effective than parallel communication RS232 is an example
for serial communication interface
24 Parallel Interface
Parallel communication is a way to sending more than one data at a time (normally eight
data bits) over to a parallel device or a Com Port For an example a computer will send
eight data bits of information to a parallel printer A very simple diagram of parallel
communication was present as Figure 2e The parallel interfaces require separated wire
8
------_------------__shyp
for sending separated data and therefor allowed faster and efficient data transmission On
the other hand to setting up a parallel communication network will be more costly than
serial communication network
1 Printer Interface
1 3 4 5 6 7 8
1 Computer Interface
2 3 4 5 6 7 8
Figure 2e A parallel Printer to Computer Interface [7 ]
25 Asynchronous and synchronous data
For two devices to communicate a way of synchronizing data must be set There are two
way ofdata formatting by using either asynchronous or synchronous
The synchronous operation is such a way that for each line data transmit it has a
separated clock to synchronous that data on a time of period For example data are
transfer once in each direction to and from the computer The synchronous data format
was show in figure 2f
While the asynchronous data is such a way that data are synchronous without clock
Each time the data are transmitting the receiver need to figure out how fast the data is
running The frame of asynchronous data has start and stops bit In another world the
frame always added with additional start and stop bit The asynchronous data format was
show in figure 2g
9
01100011100 o 1 1 1 11 0 0 0 0 001 0110 1 1 0
Unique Code
Continuous Block
Direction offlow
Figure 2f Synchronous data format I 8 ]
Start Stop d7 d6 d5 d4 d3 d2 dl dO Start
1 0 1 0 1 1 0 0I 1 I IMSB LSB
Start bit Stop bit1 Data-bits 1 I
r space mark mark space mark space mark mark space space
Serial Communication
Figure 2g Asynchronous Data Format Adopted form [8]
26 The Start Parity and Stop bits
For two machines to communicate to each other first thing both machines must agree on
the rate of speed for data transfer Second thing is the data must fonnatted for
synchronous or asynchronous operation Therefor for asynchronous operation the data
fonnatted in such a way that contains start and stop bit
271 Start bit
10
The TD line at interface device (Pin3) will go high when no data been transmit To start
transmit a data Transmit serial device will set TD line to low by means ofa start bit The
synchronous operation of DCE is waiting the TD line sign change from high bit to low
bit than DCE pauses half of a bit time and start sampling the incoming data until all the
character has been completely transmit To maintain synchronimtion DCE always
sampling the incoming data string at middle ofeach bit
272 Data bits
The data bits are the bits that contain character Nonnallyone character contains eight
bits Hence is the data bits showing character Amiddot 4tH
l start bit 41----shy Data bits j
shy
I t I Io 0 0 0 0 0
1 1deg1 1
Figure 2h The Data bits Format ( 7 ]
273 Parity bits
Four basic fonns ofparity bits are NONE EVEN ODD MARK and SPACE NONE use
for transmits a character without parity bit EVEN parity use to indicate by send logic 1
after a character if there is an odd number of logic 1 bit after a character data bit
Otherwise logic for EVEN parity goes to zero Odd parity will indicate by sending logic
1 after a data of a character bits if there is an even number of logic 1 after a characters
data bits Otherwise logic for ODD parity goes to zero Mark is logic 1 parity bit after a
data character and SPACE is logic zero after the data character
11
274 Stop bits
The stop bit indicated the end of a character The serial device was always send logic 1
for stop bit
28 Data Transmit and Receive Process
281 Transmit of a character
Several steps take before characters are transmitting from processor to modem
For an example communication between processor and 8251A USART
First the processor configures UART according to the communication protocol
Second an instruction was send to UART and set the flag TxEN Next The processor
was send the character to the data buffer ofUART Then this data buffer transfer the
character to transmit buffer for preparation for transmission Once data buffer was
complete transfer the character and ready to receive a new character the TXRDY flag
will set When processor automatically write in data buffer TXRDY flag automatically
reset
Next RTS (Ready to Send)pin output pin ofUART will alerted by modem that the bits
are about to transmit RTS pin for UART is tie together with modem RTS pin while the
modem realizes about to receive character from UART CTS pin will activated Then the
character was automatically transfer to modem The internal flag TxEMPTY will set
once the character was completely transmit from UART to modem
282 Receive of a character
The process of data receiving was also take several sequence First processor configures
UART according to standard protocol Then to receive a character the processor sends a
12
p
instruction to activated the RxE flag Next DART need to be alerted about the data going
to be transmitted DSR (Data Set Ready) will activated DSR pin of DART and modem
are tied together therefore when processor read this flags and realizes that the modem
has characters to be transmitted to DART Once DSR signal been set processor set DTR
(data terminal ready) to high And once DTR pin is asserted characters was
automatically transfer out from modem Once the characters is receive by DART it
formatted the data according to their start stop parity bits The RxRDY activated when a
character was completely receive
The bock diagram ofDART was show in ftgUre 2i
transmittedT~_B_r ~Mode Register
Transmit Register-~ I I data
I [_~~~J lt-~--r I
Receiver Register L~~~l-~~mmg =71 -_Rece~~I_v-e_r-B_-un_e=r=_-_ ~_romL--_
Devices and bullControl LogiC
l Internal Transmitter I Bus c-- ~ Clocking
--_______________rece_i_ve_r__lt=__-T Circuitary
Figure 2i USART Bloek Diagram [8 ]
28 COM Port setting
COM Port is the port that allowed computer to communicated with other device
such as modem or printer The standard personal computer normally has four
communications port COM 1 and COM 2 are assign for external port All the
13
the serial bits to parallel bits format The operation of UART mostly control by one or
more register The process of read writes data to register are through input and output
ports Figure ld showing the address of a UART for COMI and COM4
The UART have FIFO or First in First out buffer FIFO bring the meaning as the first
data to enter the buffer are first to leave The function of buffer is to hold data temporary
before it was feed to the transmission medium The modem 16550A UART have16 bytes
FIFO This means 16 bytes can be writes to UART before anything was overwrite The
16550 UART was necessary for a high-speed communication under windows or
application running under window environment
Serial port Base Register Port Address
COM 1 3F8H COM2 2F8H COM3 3E8H COM3 2E8H
Figure ld The Serial Port Base Register Port [7 ]
23 Serial Communication
Serial communication is transmission of data over a serial interface one data bit at a time
In other word data are transfer through and forth over a single wire Therefore serial
communication is more cost effective than parallel communication RS232 is an example
for serial communication interface
24 Parallel Interface
Parallel communication is a way to sending more than one data at a time (normally eight
data bits) over to a parallel device or a Com Port For an example a computer will send
eight data bits of information to a parallel printer A very simple diagram of parallel
communication was present as Figure 2e The parallel interfaces require separated wire
8
------_------------__shyp
for sending separated data and therefor allowed faster and efficient data transmission On
the other hand to setting up a parallel communication network will be more costly than
serial communication network
1 Printer Interface
1 3 4 5 6 7 8
1 Computer Interface
2 3 4 5 6 7 8
Figure 2e A parallel Printer to Computer Interface [7 ]
25 Asynchronous and synchronous data
For two devices to communicate a way of synchronizing data must be set There are two
way ofdata formatting by using either asynchronous or synchronous
The synchronous operation is such a way that for each line data transmit it has a
separated clock to synchronous that data on a time of period For example data are
transfer once in each direction to and from the computer The synchronous data format
was show in figure 2f
While the asynchronous data is such a way that data are synchronous without clock
Each time the data are transmitting the receiver need to figure out how fast the data is
running The frame of asynchronous data has start and stops bit In another world the
frame always added with additional start and stop bit The asynchronous data format was
show in figure 2g
9
01100011100 o 1 1 1 11 0 0 0 0 001 0110 1 1 0
Unique Code
Continuous Block
Direction offlow
Figure 2f Synchronous data format I 8 ]
Start Stop d7 d6 d5 d4 d3 d2 dl dO Start
1 0 1 0 1 1 0 0I 1 I IMSB LSB
Start bit Stop bit1 Data-bits 1 I
r space mark mark space mark space mark mark space space
Serial Communication
Figure 2g Asynchronous Data Format Adopted form [8]
26 The Start Parity and Stop bits
For two machines to communicate to each other first thing both machines must agree on
the rate of speed for data transfer Second thing is the data must fonnatted for
synchronous or asynchronous operation Therefor for asynchronous operation the data
fonnatted in such a way that contains start and stop bit
271 Start bit
10
The TD line at interface device (Pin3) will go high when no data been transmit To start
transmit a data Transmit serial device will set TD line to low by means ofa start bit The
synchronous operation of DCE is waiting the TD line sign change from high bit to low
bit than DCE pauses half of a bit time and start sampling the incoming data until all the
character has been completely transmit To maintain synchronimtion DCE always
sampling the incoming data string at middle ofeach bit
272 Data bits
The data bits are the bits that contain character Nonnallyone character contains eight
bits Hence is the data bits showing character Amiddot 4tH
l start bit 41----shy Data bits j
shy
I t I Io 0 0 0 0 0
1 1deg1 1
Figure 2h The Data bits Format ( 7 ]
273 Parity bits
Four basic fonns ofparity bits are NONE EVEN ODD MARK and SPACE NONE use
for transmits a character without parity bit EVEN parity use to indicate by send logic 1
after a character if there is an odd number of logic 1 bit after a character data bit
Otherwise logic for EVEN parity goes to zero Odd parity will indicate by sending logic
1 after a data of a character bits if there is an even number of logic 1 after a characters
data bits Otherwise logic for ODD parity goes to zero Mark is logic 1 parity bit after a
data character and SPACE is logic zero after the data character
11
274 Stop bits
The stop bit indicated the end of a character The serial device was always send logic 1
for stop bit
28 Data Transmit and Receive Process
281 Transmit of a character
Several steps take before characters are transmitting from processor to modem
For an example communication between processor and 8251A USART
First the processor configures UART according to the communication protocol
Second an instruction was send to UART and set the flag TxEN Next The processor
was send the character to the data buffer ofUART Then this data buffer transfer the
character to transmit buffer for preparation for transmission Once data buffer was
complete transfer the character and ready to receive a new character the TXRDY flag
will set When processor automatically write in data buffer TXRDY flag automatically
reset
Next RTS (Ready to Send)pin output pin ofUART will alerted by modem that the bits
are about to transmit RTS pin for UART is tie together with modem RTS pin while the
modem realizes about to receive character from UART CTS pin will activated Then the
character was automatically transfer to modem The internal flag TxEMPTY will set
once the character was completely transmit from UART to modem
282 Receive of a character
The process of data receiving was also take several sequence First processor configures
UART according to standard protocol Then to receive a character the processor sends a
12
p
instruction to activated the RxE flag Next DART need to be alerted about the data going
to be transmitted DSR (Data Set Ready) will activated DSR pin of DART and modem
are tied together therefore when processor read this flags and realizes that the modem
has characters to be transmitted to DART Once DSR signal been set processor set DTR
(data terminal ready) to high And once DTR pin is asserted characters was
automatically transfer out from modem Once the characters is receive by DART it
formatted the data according to their start stop parity bits The RxRDY activated when a
character was completely receive
The bock diagram ofDART was show in ftgUre 2i
transmittedT~_B_r ~Mode Register
Transmit Register-~ I I data
I [_~~~J lt-~--r I
Receiver Register L~~~l-~~mmg =71 -_Rece~~I_v-e_r-B_-un_e=r=_-_ ~_romL--_
Devices and bullControl LogiC
l Internal Transmitter I Bus c-- ~ Clocking
--_______________rece_i_ve_r__lt=__-T Circuitary
Figure 2i USART Bloek Diagram [8 ]
28 COM Port setting
COM Port is the port that allowed computer to communicated with other device
such as modem or printer The standard personal computer normally has four
communications port COM 1 and COM 2 are assign for external port All the
13
------_------------__shyp
for sending separated data and therefor allowed faster and efficient data transmission On
the other hand to setting up a parallel communication network will be more costly than
serial communication network
1 Printer Interface
1 3 4 5 6 7 8
1 Computer Interface
2 3 4 5 6 7 8
Figure 2e A parallel Printer to Computer Interface [7 ]
25 Asynchronous and synchronous data
For two devices to communicate a way of synchronizing data must be set There are two
way ofdata formatting by using either asynchronous or synchronous
The synchronous operation is such a way that for each line data transmit it has a
separated clock to synchronous that data on a time of period For example data are
transfer once in each direction to and from the computer The synchronous data format
was show in figure 2f
While the asynchronous data is such a way that data are synchronous without clock
Each time the data are transmitting the receiver need to figure out how fast the data is
running The frame of asynchronous data has start and stops bit In another world the
frame always added with additional start and stop bit The asynchronous data format was
show in figure 2g
9
01100011100 o 1 1 1 11 0 0 0 0 001 0110 1 1 0
Unique Code
Continuous Block
Direction offlow
Figure 2f Synchronous data format I 8 ]
Start Stop d7 d6 d5 d4 d3 d2 dl dO Start
1 0 1 0 1 1 0 0I 1 I IMSB LSB
Start bit Stop bit1 Data-bits 1 I
r space mark mark space mark space mark mark space space
Serial Communication
Figure 2g Asynchronous Data Format Adopted form [8]
26 The Start Parity and Stop bits
For two machines to communicate to each other first thing both machines must agree on
the rate of speed for data transfer Second thing is the data must fonnatted for
synchronous or asynchronous operation Therefor for asynchronous operation the data
fonnatted in such a way that contains start and stop bit
271 Start bit
10
The TD line at interface device (Pin3) will go high when no data been transmit To start
transmit a data Transmit serial device will set TD line to low by means ofa start bit The
synchronous operation of DCE is waiting the TD line sign change from high bit to low
bit than DCE pauses half of a bit time and start sampling the incoming data until all the
character has been completely transmit To maintain synchronimtion DCE always
sampling the incoming data string at middle ofeach bit
272 Data bits
The data bits are the bits that contain character Nonnallyone character contains eight
bits Hence is the data bits showing character Amiddot 4tH
l start bit 41----shy Data bits j
shy
I t I Io 0 0 0 0 0
1 1deg1 1
Figure 2h The Data bits Format ( 7 ]
273 Parity bits
Four basic fonns ofparity bits are NONE EVEN ODD MARK and SPACE NONE use
for transmits a character without parity bit EVEN parity use to indicate by send logic 1
after a character if there is an odd number of logic 1 bit after a character data bit
Otherwise logic for EVEN parity goes to zero Odd parity will indicate by sending logic
1 after a data of a character bits if there is an even number of logic 1 after a characters
data bits Otherwise logic for ODD parity goes to zero Mark is logic 1 parity bit after a
data character and SPACE is logic zero after the data character
11
274 Stop bits
The stop bit indicated the end of a character The serial device was always send logic 1
for stop bit
28 Data Transmit and Receive Process
281 Transmit of a character
Several steps take before characters are transmitting from processor to modem
For an example communication between processor and 8251A USART
First the processor configures UART according to the communication protocol
Second an instruction was send to UART and set the flag TxEN Next The processor
was send the character to the data buffer ofUART Then this data buffer transfer the
character to transmit buffer for preparation for transmission Once data buffer was
complete transfer the character and ready to receive a new character the TXRDY flag
will set When processor automatically write in data buffer TXRDY flag automatically
reset
Next RTS (Ready to Send)pin output pin ofUART will alerted by modem that the bits
are about to transmit RTS pin for UART is tie together with modem RTS pin while the
modem realizes about to receive character from UART CTS pin will activated Then the
character was automatically transfer to modem The internal flag TxEMPTY will set
once the character was completely transmit from UART to modem
282 Receive of a character
The process of data receiving was also take several sequence First processor configures
UART according to standard protocol Then to receive a character the processor sends a
12
p
instruction to activated the RxE flag Next DART need to be alerted about the data going
to be transmitted DSR (Data Set Ready) will activated DSR pin of DART and modem
are tied together therefore when processor read this flags and realizes that the modem
has characters to be transmitted to DART Once DSR signal been set processor set DTR
(data terminal ready) to high And once DTR pin is asserted characters was
automatically transfer out from modem Once the characters is receive by DART it
formatted the data according to their start stop parity bits The RxRDY activated when a
character was completely receive
The bock diagram ofDART was show in ftgUre 2i
transmittedT~_B_r ~Mode Register
Transmit Register-~ I I data
I [_~~~J lt-~--r I
Receiver Register L~~~l-~~mmg =71 -_Rece~~I_v-e_r-B_-un_e=r=_-_ ~_romL--_
Devices and bullControl LogiC
l Internal Transmitter I Bus c-- ~ Clocking
--_______________rece_i_ve_r__lt=__-T Circuitary
Figure 2i USART Bloek Diagram [8 ]
28 COM Port setting
COM Port is the port that allowed computer to communicated with other device
such as modem or printer The standard personal computer normally has four
communications port COM 1 and COM 2 are assign for external port All the
13
01100011100 o 1 1 1 11 0 0 0 0 001 0110 1 1 0
Unique Code
Continuous Block
Direction offlow
Figure 2f Synchronous data format I 8 ]
Start Stop d7 d6 d5 d4 d3 d2 dl dO Start
1 0 1 0 1 1 0 0I 1 I IMSB LSB
Start bit Stop bit1 Data-bits 1 I
r space mark mark space mark space mark mark space space
Serial Communication
Figure 2g Asynchronous Data Format Adopted form [8]
26 The Start Parity and Stop bits
For two machines to communicate to each other first thing both machines must agree on
the rate of speed for data transfer Second thing is the data must fonnatted for
synchronous or asynchronous operation Therefor for asynchronous operation the data
fonnatted in such a way that contains start and stop bit
271 Start bit
10
The TD line at interface device (Pin3) will go high when no data been transmit To start
transmit a data Transmit serial device will set TD line to low by means ofa start bit The
synchronous operation of DCE is waiting the TD line sign change from high bit to low
bit than DCE pauses half of a bit time and start sampling the incoming data until all the
character has been completely transmit To maintain synchronimtion DCE always
sampling the incoming data string at middle ofeach bit
272 Data bits
The data bits are the bits that contain character Nonnallyone character contains eight
bits Hence is the data bits showing character Amiddot 4tH
l start bit 41----shy Data bits j
shy
I t I Io 0 0 0 0 0
1 1deg1 1
Figure 2h The Data bits Format ( 7 ]
273 Parity bits
Four basic fonns ofparity bits are NONE EVEN ODD MARK and SPACE NONE use
for transmits a character without parity bit EVEN parity use to indicate by send logic 1
after a character if there is an odd number of logic 1 bit after a character data bit
Otherwise logic for EVEN parity goes to zero Odd parity will indicate by sending logic
1 after a data of a character bits if there is an even number of logic 1 after a characters
data bits Otherwise logic for ODD parity goes to zero Mark is logic 1 parity bit after a
data character and SPACE is logic zero after the data character
11
274 Stop bits
The stop bit indicated the end of a character The serial device was always send logic 1
for stop bit
28 Data Transmit and Receive Process
281 Transmit of a character
Several steps take before characters are transmitting from processor to modem
For an example communication between processor and 8251A USART
First the processor configures UART according to the communication protocol
Second an instruction was send to UART and set the flag TxEN Next The processor
was send the character to the data buffer ofUART Then this data buffer transfer the
character to transmit buffer for preparation for transmission Once data buffer was
complete transfer the character and ready to receive a new character the TXRDY flag
will set When processor automatically write in data buffer TXRDY flag automatically
reset
Next RTS (Ready to Send)pin output pin ofUART will alerted by modem that the bits
are about to transmit RTS pin for UART is tie together with modem RTS pin while the
modem realizes about to receive character from UART CTS pin will activated Then the
character was automatically transfer to modem The internal flag TxEMPTY will set
once the character was completely transmit from UART to modem
282 Receive of a character
The process of data receiving was also take several sequence First processor configures
UART according to standard protocol Then to receive a character the processor sends a
12
p
instruction to activated the RxE flag Next DART need to be alerted about the data going
to be transmitted DSR (Data Set Ready) will activated DSR pin of DART and modem
are tied together therefore when processor read this flags and realizes that the modem
has characters to be transmitted to DART Once DSR signal been set processor set DTR
(data terminal ready) to high And once DTR pin is asserted characters was
automatically transfer out from modem Once the characters is receive by DART it
formatted the data according to their start stop parity bits The RxRDY activated when a
character was completely receive
The bock diagram ofDART was show in ftgUre 2i
transmittedT~_B_r ~Mode Register
Transmit Register-~ I I data
I [_~~~J lt-~--r I
Receiver Register L~~~l-~~mmg =71 -_Rece~~I_v-e_r-B_-un_e=r=_-_ ~_romL--_
Devices and bullControl LogiC
l Internal Transmitter I Bus c-- ~ Clocking
--_______________rece_i_ve_r__lt=__-T Circuitary
Figure 2i USART Bloek Diagram [8 ]
28 COM Port setting
COM Port is the port that allowed computer to communicated with other device
such as modem or printer The standard personal computer normally has four
communications port COM 1 and COM 2 are assign for external port All the
13
The TD line at interface device (Pin3) will go high when no data been transmit To start
transmit a data Transmit serial device will set TD line to low by means ofa start bit The
synchronous operation of DCE is waiting the TD line sign change from high bit to low
bit than DCE pauses half of a bit time and start sampling the incoming data until all the
character has been completely transmit To maintain synchronimtion DCE always
sampling the incoming data string at middle ofeach bit
272 Data bits
The data bits are the bits that contain character Nonnallyone character contains eight
bits Hence is the data bits showing character Amiddot 4tH
l start bit 41----shy Data bits j
shy
I t I Io 0 0 0 0 0
1 1deg1 1
Figure 2h The Data bits Format ( 7 ]
273 Parity bits
Four basic fonns ofparity bits are NONE EVEN ODD MARK and SPACE NONE use
for transmits a character without parity bit EVEN parity use to indicate by send logic 1
after a character if there is an odd number of logic 1 bit after a character data bit
Otherwise logic for EVEN parity goes to zero Odd parity will indicate by sending logic
1 after a data of a character bits if there is an even number of logic 1 after a characters
data bits Otherwise logic for ODD parity goes to zero Mark is logic 1 parity bit after a
data character and SPACE is logic zero after the data character
11
274 Stop bits
The stop bit indicated the end of a character The serial device was always send logic 1
for stop bit
28 Data Transmit and Receive Process
281 Transmit of a character
Several steps take before characters are transmitting from processor to modem
For an example communication between processor and 8251A USART
First the processor configures UART according to the communication protocol
Second an instruction was send to UART and set the flag TxEN Next The processor
was send the character to the data buffer ofUART Then this data buffer transfer the
character to transmit buffer for preparation for transmission Once data buffer was
complete transfer the character and ready to receive a new character the TXRDY flag
will set When processor automatically write in data buffer TXRDY flag automatically
reset
Next RTS (Ready to Send)pin output pin ofUART will alerted by modem that the bits
are about to transmit RTS pin for UART is tie together with modem RTS pin while the
modem realizes about to receive character from UART CTS pin will activated Then the
character was automatically transfer to modem The internal flag TxEMPTY will set
once the character was completely transmit from UART to modem
282 Receive of a character
The process of data receiving was also take several sequence First processor configures
UART according to standard protocol Then to receive a character the processor sends a
12
p
instruction to activated the RxE flag Next DART need to be alerted about the data going
to be transmitted DSR (Data Set Ready) will activated DSR pin of DART and modem
are tied together therefore when processor read this flags and realizes that the modem
has characters to be transmitted to DART Once DSR signal been set processor set DTR
(data terminal ready) to high And once DTR pin is asserted characters was
automatically transfer out from modem Once the characters is receive by DART it
formatted the data according to their start stop parity bits The RxRDY activated when a
character was completely receive
The bock diagram ofDART was show in ftgUre 2i
transmittedT~_B_r ~Mode Register
Transmit Register-~ I I data
I [_~~~J lt-~--r I
Receiver Register L~~~l-~~mmg =71 -_Rece~~I_v-e_r-B_-un_e=r=_-_ ~_romL--_
Devices and bullControl LogiC
l Internal Transmitter I Bus c-- ~ Clocking
--_______________rece_i_ve_r__lt=__-T Circuitary
Figure 2i USART Bloek Diagram [8 ]
28 COM Port setting
COM Port is the port that allowed computer to communicated with other device
such as modem or printer The standard personal computer normally has four
communications port COM 1 and COM 2 are assign for external port All the
13
274 Stop bits
The stop bit indicated the end of a character The serial device was always send logic 1
for stop bit
28 Data Transmit and Receive Process
281 Transmit of a character
Several steps take before characters are transmitting from processor to modem
For an example communication between processor and 8251A USART
First the processor configures UART according to the communication protocol
Second an instruction was send to UART and set the flag TxEN Next The processor
was send the character to the data buffer ofUART Then this data buffer transfer the
character to transmit buffer for preparation for transmission Once data buffer was
complete transfer the character and ready to receive a new character the TXRDY flag
will set When processor automatically write in data buffer TXRDY flag automatically
reset
Next RTS (Ready to Send)pin output pin ofUART will alerted by modem that the bits
are about to transmit RTS pin for UART is tie together with modem RTS pin while the
modem realizes about to receive character from UART CTS pin will activated Then the
character was automatically transfer to modem The internal flag TxEMPTY will set
once the character was completely transmit from UART to modem
282 Receive of a character
The process of data receiving was also take several sequence First processor configures
UART according to standard protocol Then to receive a character the processor sends a
12
p
instruction to activated the RxE flag Next DART need to be alerted about the data going
to be transmitted DSR (Data Set Ready) will activated DSR pin of DART and modem
are tied together therefore when processor read this flags and realizes that the modem
has characters to be transmitted to DART Once DSR signal been set processor set DTR
(data terminal ready) to high And once DTR pin is asserted characters was
automatically transfer out from modem Once the characters is receive by DART it
formatted the data according to their start stop parity bits The RxRDY activated when a
character was completely receive
The bock diagram ofDART was show in ftgUre 2i
transmittedT~_B_r ~Mode Register
Transmit Register-~ I I data
I [_~~~J lt-~--r I
Receiver Register L~~~l-~~mmg =71 -_Rece~~I_v-e_r-B_-un_e=r=_-_ ~_romL--_
Devices and bullControl LogiC
l Internal Transmitter I Bus c-- ~ Clocking
--_______________rece_i_ve_r__lt=__-T Circuitary
Figure 2i USART Bloek Diagram [8 ]
28 COM Port setting
COM Port is the port that allowed computer to communicated with other device
such as modem or printer The standard personal computer normally has four
communications port COM 1 and COM 2 are assign for external port All the
13
p
instruction to activated the RxE flag Next DART need to be alerted about the data going
to be transmitted DSR (Data Set Ready) will activated DSR pin of DART and modem
are tied together therefore when processor read this flags and realizes that the modem
has characters to be transmitted to DART Once DSR signal been set processor set DTR
(data terminal ready) to high And once DTR pin is asserted characters was
automatically transfer out from modem Once the characters is receive by DART it
formatted the data according to their start stop parity bits The RxRDY activated when a
character was completely receive
The bock diagram ofDART was show in ftgUre 2i
transmittedT~_B_r ~Mode Register
Transmit Register-~ I I data
I [_~~~J lt-~--r I
Receiver Register L~~~l-~~mmg =71 -_Rece~~I_v-e_r-B_-un_e=r=_-_ ~_romL--_
Devices and bullControl LogiC
l Internal Transmitter I Bus c-- ~ Clocking
--_______________rece_i_ve_r__lt=__-T Circuitary
Figure 2i USART Bloek Diagram [8 ]
28 COM Port setting
COM Port is the port that allowed computer to communicated with other device
such as modem or printer The standard personal computer normally has four
communications port COM 1 and COM 2 are assign for external port All the
13
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