Transparent connectivity for

embedded system design

1

Abstract

embedded system design is a topic of multidisciplinary fields..

for embedded system design, seamless connectivity should bebetween the hardware and software.

seamless connectivity i.e. development of transparent bridge.

Here a USB/SPI transparent bridge is used to interface anembedded system to a PC.

2

Abstract

A device driver for the USB/SPI bridge provides a straightforwardapplication programming interface to the embedded system

The bridge consist of hardware module that transmits the embedded system data through SPI to a PC using USB.

3

Introduction

Some protocols, like the SPI , are used to network microcontrollerto peripheral devices .

Many microcontrollers have integrated SPI hardware.

The Serial Peripheral Interface Bus or SPI is a synchronous serialdata link.

SPI bus operates in full duplex mode.

4

Introduction Serial peripheral interface bus communicate in master/slave mode.

The SPI bus uses four wires or logic signals.•SCLK — Serial Clock (output from master)•MOSI — Master Output, Slave Input (output from master)•MISO — Master Input, Slave Output (output from slave)•SS — Slave Select (active low; output from master)

5

Introduction

MOSI and MISO are the two data lines that allow both the master and slave devices to exchange data simultaneously.

The control line, slave select (SS), is activated when the master is about to initiate a data transfer to a slave device.

6

Introduction

In a multiple slaves system, the data and clock lines are shared byall the slaves, but all slaves need a dedicated slave select line.

7

Introduction

To begin a communication, the master first configures the clock,using a frequency less than or equal to the maximum frequency theslave device supports.

The master then pulls the slave select low for the selection ofdesired slave.

8

Introduction

During each SPI clock cycle, a full duplex data transmission occurs:

•the master sends a bit on the MOSI line; the slave reads it fromthat same line

•the slave sends a bit on the MISO line; the master reads it fromthat same line

After data completion , SS to logic high. 9

Introduction

All devices

• on a SPI bus located on the same circuit board andpermanently connected to one another.

•With USB physically added or removed from USB at anytime.

10

Introduction USB establish communication between devices and host controller.

Each host controller may provide one or more USB ports.

USB

11

IntroductionThe USB uses four wires to transfer data

•VBUS and Ground to carry a 5-volt signal• D+ and D- wires carry the data and signaling

information

12

Introduction

USB does not have a clock signal.actually clock signal is embeddedinto the data stream.

Furthermore, a USB device requires a device driver to access theUSB device through the facilities of the USB host and the PC’s operating system.

The driver should provide a straightforward interface to the device..

13

System overview

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USB/SPI bridge system have three basic modules:-1) Target system( embedded system)2) Target application (PC & its OS)3) USB/SPI bridge

Fig-Block diagram of USB/SPI bridge system

The USB/SPI bridge module links the target system and target application module.

The target application module is completely hidden by the USB/SPI bridge module.

The USB/SPI bridge module consists:-a) microcontrollerb) USB node controllerc) device driver

System overview The USB/SPI Bridge creates a transparent link between an SPI

device and the application layer of a PC.

The hardware module of USB/SPI bridge recieves data via

SPI from an embedded system a PC over USB

Data may also flow in the opposite direction.

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The bridge device driver completes the link to the application layer of a PC..

Conclusion

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The design of a transparent USB/SPI bridge will aid in the design ofembedded systems.

The USB/SPI Bridge allows transparent connectivity between an embedded system and a personal computer.

The bridge consists of a hardware module that transfers data from an embedded system through the SPI to a PC using a USB.

References

17

1. “Introduction to Serial Peripheral Interface,” Embedded.com, 2007

2. USBN9603 Datasheet:http://www.national.com/ds.cgi/US/USBN9603.pdf

3. Universal Serial Bus Specification,Revision 1.1, September 23, 1998:http://www.usb.org/developers/docs/usbspec.zip

4. http://en.wikipedia.org/wiki/Serial_Peripheral_Interface_Bus5. http://en.wikipedia.org/wiki/Usb