CAN.tri 05111106. Noi Dung Bao Cao

8/6/2019 CAN.tri 05111106. Noi Dung Bao Cao

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SVTH:o Minh Tr 05111106 - 1 - GVHD: L Tn Cng

CHNG I

GII THIU CHUNG

1. 1 Gii thiu CAN

Controller Area Network (CAN) l giao thc giao tip ni tip h tr mnh chonhng h thng iu khin thi gian thc phn b (distributed realtime controlsystem) vinnh, bo mt vc bit chng nhiu cc k tt.

CANu tinc pht trin bi nh cung cp ph tng xe t ca c RobertBosch vo gia nhng nm 80. tha mnyucu ngy cngnhiu cakhch hngtrong vn an ton v tin nghi, v tuntheoyu cu vic gim bt nhim v tiuthnng lng, ngnh cng nghip t pht trin rt nhiu h thngin t nh hthng chng trt bnh xe, b iu khin ng c, iu ha nhit , b ng cav.vVi mcch chnhl lm cho nhng h thng xe ttrnn anton,nnh vtit kim nhin liu trong khi gim thiu vic i dy chng cht, n gin ha hthng v tit kimchi ph sn xut, thmng CANc phttrin.

Ngay t khi mi ra i, mng CAN c chp nhn v ng dng mt cchrng ri trong cc lnh vc cng nghip, ch to t, xe ti. Vi thi gian, CANcngtrnn thngdng hn v tnh hiu qu,n nh,n gin, mvc bit lchi phr. Nc s dng vi vic truyn d liu ln,png thi gian thc v trongmitrng khc nhau. Cui cng, truyn tc caortn nh. l l do ti saochngc s dng trong nhiu ngnh cng nghip khc ngoi xe hi nh cc my nngnghip, tu ngm, cc dng c y khoa,my dt, v.v

Ngy nay, CAN c chun ha thnh tiu chun ISO11898. Hu nh minh sn xut chip ln nh: Intel, NEC, siemens, Motorola, Maxim IC, Fairchild,Microchip, Philips, Texas Instrument, Mitsubishi,Hitachi, STmicro...u csn xut rachip CAN, hoc ctch hp CAN vo thnh periperalca viiu khin. Vic thc hinchun CANtrnn cc kn gin nhs h trt rt nhiu nhsn xut chip.

im ni tri nhtchun CAN l tnhnnhv an ton (reliability and safety).Nhcch pht hin v x l li cc mnh, li CAN messages hu nhc pht hin.Theothng k, xc sut mt messageca CAN b li khngc pht hin l:

Hnh 1.1. Tnh n nh ca CAN

V d: chorng nu gi s c 0.7s thmi trng tcng lnng truyn CANlmli 1 bit. V gi s tc truyn l 500kbits/s. Hotng 8h/ngy v 365ngy/nm. Th trongvng 1000 nmtrung bnh s cmt frameb lim khng pht hin.


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Min ng dng ca CAN tri rng (from hight speed networks to low costmultiplex wiring) : h thng in xe t, xe ti, n v iu khin ng c(engine control units), sensor, PLC comunication, thit b y t. Ngy nay CANchim lnh trong ngnh cng nghip t. Trong nhng chic xe hi i mi thngc mt mng CAN high speed dng iu khin ng c v thng mt mngCANlowspeed dngiu khin nhng thit b khc nh king hu, light

Hnh 1.2. ng dng mng CAN trong iu khin xe hiChun Field bus Device net, CANopen, J1939 thng dng trong cng

nghip chnh l chun CAN mrng. (Physicallayer v MAC sublayer ca ccchunny l CAN).

1.2 Tm tt tng quan:

CAN l mt chun ISO (ISO 11898) cho tryn thng ni tip.Giao thc c BOSCH xy dng vo nm 1980 cho cc ng dng t ng.

Ngy nay CAN c s dng rng ri trong cng nghip t ng.Chun CAN bao gm:

1.Tng vt l.2.Tng lin kt d liu:-Vi loi thng ip-Cc chun phn x cho truy cp bus-Cc phng php d li v giam li


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CHNG II

CU TO V NG DNG MNG CAN

2.1 CAN protocol overview( tng quan v giao thc CAN)Chunu tin ca CAN l chun ISOP 11898-2nh nghacc tnh cht caCANHigh Speed.

Mt v d v mng CAN trong thc t

Hnh 2.1. Mt v d v mng CAN

Cng ngh cp ca mng CAN c ng dy dn n gin, gim ti thiu hintng si tn hiu. s truyn d liu thc hin nhcp dy truyn tn hiu vi sai,cngha l chng tao s khc nhau gia 2ng(CAN H v CANL).ngdy buskt thcbngin tr120 ohm(thp nht l 108ohm vtia l 132 ohm)miu

Mng CAN c to thnh bi mt nhm cc nodes. Mi node c th giao tipvi bt k nodes no khc trongmng. Vic giao tipc thc hin bng vic truyni v nhn cc gi d liu -gi lmessage. Mi loi message trong mng CANcgnchomt ID - snhdanh - ty theo mcu tinca message.


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Hinh 2.2: Mt nt mng CAN

Mng CAN thuc loi message base system, khc vi address base system, miloi message c gn mt ID. Nhng h thng address base th mi node c gncho mt ID. Message base system c tnhmhnvkhi thm, bt mt nodehay thaymt nhm nodebng mt nodephc tp hn khng lmnh hngn c h thng. Cth c vi node nhn messagev cngthc hin mt task. H thngiu khin phn bda trn mng CAN c tnh m, d dng thay i m khngcn phi thit k li tonb h thng.

Mi nodecth nhn nhiu loimessage khcnhau, ngc li mt messagec thc nhn bi nhiu node v cng vicc thc hin mt cchng b trong h thngphn b.

ID ca message ph thuc vo mc u tin ca message. iu ny chophp phn tch response time ca tng message. ngha quan trng trong vic thitk h thng nhng thi gian thc. Trc khi c mng CAN, la chn duy nht chomng giaotip trongh thng thi gianthc l mng token ringchm chp.


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Hnh2.3 : M hnh mng CAN

Tiu chun ISO11898nh ngha hai lp Physical layer v Datalinklayer.

Lp Physical layernh ngha cch biu din/thu nhn bit 0 bit 1,cchnh thi v


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ng b

Lp Datalink layerc chialm 2lp nh llogical linkcontrol(LLC) v MediumAccess Control (MAC):nh ngha frame truyn v nhng nguyntc arbittrationtrnh trng hp chai Master cng truynng thi.

Hnh 2.4: Cc lp layer giao tip

Ngoi ra,chun CAN cnnh ngha nhiucch khc kim trali, x llicch kim tra v x lli chia lm 5 loi li: Bit error,Stuff error, CRC error,Formerror, ACK error.

2.2 Lp vt l

2.2.1 None-return-to-zero

Mi bit trong mng CAN c m ha bng phng php None-return-

to-zero (NRZ method). Trong sut qu trnh ca mt bit, mc in p ca dyc gi nguyn, c ngha trong sut qu trnh mt btc to, gi tr ca n gikhngi.

Hnh 2.5: NRZ method


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2.2.2 Bit tuffingMt trong nhnguim ca cch m haNRZlmc ca bitc gi trong

sut qu trnh ca n. iu ny to ra vn vnnh nu mt lng ln bitging nhau ni tip. K thut Bit Stuffing pt tng mt bitc gi tr ngc likhi n pht hin5 bit lintip trong khi truyn.

Hnh 2.6: K thut Bit Stuffing

2.2.3. Bit timingTanh ngha thi giann v nh nht, lTime Quantum.Thi gian cbn

ny lmt phn s ca thi gian daong ca bus.Mt bit khong 8n 25 quanta.

Hnh 2.7: Gin thi gian

2.2.4 di ca mt bus:

dica mt bus ph thuc vo nhng thngs sau:

- tr lan truyn trnng dy ca bus

- Skhc nhau ca thi gian TimeQuantum (nh nghatrn), v s khcnhau ca xung clock ti ccnt

- Bin tnhiu thayi theoin trca cp vtng trvoca ccnt


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Hnh 2.8: Tc t l nghch vi di bus

Bng 2.9 : Vn tc di Bit time

Cnch rng bt c modulno kt ni vo mt bus CANphic h trvi tc ti thiu l 20kbit/s. s dng bus c di hn 200 m, cn thit phis dng mt optocoupleur, v s dngbus di hn1 km, phi cn mt h thng ktni trung gian nh repeater hoc bridge.

2.2.5 Trng thi dominant v recessive

lp vt l, Bus CAN nh ngha hai trng thi l dominant v recessive,tng ng vi hai trng thi l 0 v 1. Trng thi dominant chim u th so vitrng thi recessive.Buschtrng thi reccessive khi khng c node no phti trng thi dominant. iu ny to ra kh nng gii quyt chanhchp khi nhiuhn mt Master cngmun chim quyn s dng bus.

Bi tnhcht vt lca bus,cn thit phi phnbit 2 dng truyn:

- Truyn CAN low speed

- Truyn CAN high speed

Bng sau tng kt nhng tnhchtcbn khc nhau gia 2 dng,c bit ltc:


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Thng s CAN low speed CAN highspeedTc 125 kb/s 125 kb/s ti 1Mb/ss nt trn bus 2 ti 20 2ti 30Trng thidominant

CAN H= 4V ; CAN L=1V CAN H = 3,25V; CAN L = 1,5V

Trng thi

recessive

CAN H = 1,75V;CANL=3,25V CANH =2,5V ; CAN L = 2,5V

tnh cht ca cap 30pF gia cpv dy 2*120ohmMc in p cungcp

5V 5V

Bng 2.10: So snh CAN low speed v CAN high speed

Hnh 2.11: in p ca CAN low speed

Hnh 2.12: in p ca CAN high speed


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V tnhcht vi sai trnng truyn tn hiu ca busCAN, s min tr tcngin t c bom v 2dyca busu b tcng nh nhaucngmt lcbi tn hiu nhiu.

Hnh 2.13: S khng nhiu vi nh hng ca in t

2.3. C ch giao tip

c trng ca CAN l phng php nh a ch v giao tip hng i tng,trong khi hu ht cc h thng bus thng khc u giao tip da vo a ch cctrm.Mi thng tin trao i trong mng c coi nh mt i tng , c gn mt ms cn cc .Thng tin c gi trn bus theo kiu truyn thng bo vi di c thkhc nhau.

Cc thng bo khng c gi ti mt a ch nht nh m bt c trm no cngc th nhn theo nhu cu.Ni dung mi thng bo c cc trm phn bit qua mt mcn cc ( IDENTIFIER).M cn cc khng ni ln a ch ch ca thng bo, m chbiu din ngha ca d liu trong thng bo.V th, mi trm trn mng c th t quytnh tip nhn v x l thng bo hay khng tip nhn thng bo qua phng thc lcthng bo(message filtering).Cng nh x dng phng thc lc thng bo, nhiu trmc th ng thi nhn cng mt thng bo v c cc phn ng khc nhau.

Mt trm c th yu cu mt trm khc gi d liu bng cch gi 1 khung REMOTEFRAME.Trm c kh nng cung cp ni dung thng tin s gi tr li mt khung dliu DATA FRAME c cng m cn cc vi khung yu cu.Bn cnh tnh nng ngin, c ch giao tip hng i tng CAN cn mang li tnh linh hot v tnh nhtqun d liu ca h thng.Mt trm CAN khng cn bit thng tin cu hnh h thng ( vd a ch trm), nn vic b sung hay b i mt trm trong mng khng i hi bt c

mt s thay i no v phn cng hay phn mm cc trm khc.Trong mt mng CAN, c th chc chn rng mt thng bo hoc c tt c cc trm quan tm tip nhn ngthi, hoc khng c trm no tip nhn.tnh nht qun d liu c m bo qua cc

phng php gi ng lot v x l li.

2.4. Gii quyt tranh chp trn bus

Phng thc giao tip ca bus CAN l s pht tn thng tin (broadcast):mi im kt ni vo mng thu nhn fame truyn t nt pht. Sau , ni nt s


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quyt nh vic s l message, c tr li hay khng, c phn hi hay khngCchthc nyging nh s pht thng tinvngi ca mt trm pht thanh,:khinhn c thng tin v ng i, ngi li xe c th thay i l trnh ca anh ta,dng xe haythayi ti x hoc chnglm g c

Giao thcCAN cho phpccnt khc nhaua d liucng lc v mtqu trnhnhanh chng ,nnh ca cch arbitrations xcnhxem nt nocphtu tin.

s l thi gian thc, d liu phi c truyn nhanh. iu ny nhhng khng ch ng truyn vt lcho php ti 1Mbit/s, mcni hi mt scp pht nhanh bus trong trng hp xung i, khi m rt nhiu nt mun truynng thi. Khi traoi d liu trn bus, th t s c xcnh da vo loithngtin.V du,cc gi tr hay bini nhanh,nh trng thi ca mt cm bin, hay phnhi ca mtng c, phic truyn lintc vi tr thp nht, hn lcc gi trkhcnh nhit cang c, cc gi tr thay i t. Trong mng CAN , phn IDca mi message, lmt t gm11 bit (version 2.0A) xcnh mcu tin. Phnutin ny nm u mi message. Mc u tin c xc nh bi 7 bit choverdion 2.0A, ti 127 mc v mc 128 l0000000 theo NMT(Netword Management)

Quy trnh arbitration ca busda trn phn gii tng bit, theo nhng ntang tranhchp, phtng thi trn bus. Nt nomcu tin thp hn s mt s cnh tranhvintcmcu tincao.

Hnh 2.14: Gii quyt tranh chp trn bus

2.5. CAN frame ( cu trc bc in)Mt khung truyn c dng sau:

Hnh 2.15: Khung truyn

Chun CAN nh ngha bn loi Frame: Data frame dng khi node mun truynd liu ti cc node khc. Remote frame dng yu cu truyn data frame. Errorframe v overload framedng trong vic x lli.

Dataframe: dng truyn i mt message. C hai dng: standard frame vextended frame


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Hnh 2.16 CAN data frame

Standard frame: bt u bng 1 bit start of frame (SOF) lun trng thidominant, 11bit ID tip theo, 1 bit Remote Transmit Request (RTR) phn bitremote frame v data frame nu bng dominant ngha l data frame, nu bngrecesivengha l remoteframe. Tipn l1 bit Identifier Extension (IDE) phnbit gia Standard frame (dominant) v extended frame (reccesive). Tip theol1bit r0luntrng thi dominant. Tipn l3bitData Length Control cho bits lng byte data cu frame. Tip n l 0 n 8 bytes data. Tip n l 15 bitCRC v 1bit CRC delimiter. tipn l 1bit Acknoledge v 1 bitdelimiter,tip theol 7bits End of frame lun trng thi recesive. cui cng l khong cch ti thiugia hai frametruyn inter-frame space (IFS).

Hnh 2.17. CAN standard frame


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Extended frame: gn ging nh standard frame, vc 29 bit ID:

Hnh 2.18.CAN extended frame

Chi tit cc phn khc nhau trong mt khung truyn d liu:

Start of frame:Nm phn u ca mt farme d liu hay Remote frame, lun trng thi

dominant. Mt ntc th btu truyn d liu nu busrnh. Sau tt c ccntu

ng b sau SOF ca nt btu truyn.

CRCField:

Hnh2.19:CRCField

CRCField bao gm mt chui gm 15 bit v CRC Delimiter (l 1 bit reccesive)

Mt chui CRC (Cyclic Redundancy Code) cho php kim tra s nguyn vnca d liu truyn. Tt c cc nt nhn phi thc hin quy trnh kim tra ny. Ch vng SOF, vng tranh chp, vng iu khin v vng d liuc s dng tnh ton chui CRC.

Trn thc t, di cci ca frame khng vt qu 215 bit cho mt chui CRC 15 bit.

ACKField:

Gm 2 bit : ACK slot v ACK Delimiter (l 1 bit recesive)

- mt nt ang truyn s gi mt bit recesive trong ACK slot

- mt nt nhn ng message thng bo cho nt truyn s gi 1 bit dominanttrong ACK slot


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Remote frame( khung yu cu d liu): dng yu cu truyn data frame timt ntkhc. Gn ging dataframe nhng c DLC=0 v khng c datafield.

Hnh 2.20: CAN remote frame

Error frame:c pht ra khi nodepht hin li

Frame li bao gm 2 phn:- Cli

- Phndelimiter

Hnh 2.21: CAN error frame

Overload frame:Dng khi frame b trn bm, nhm to mt khong cch thi gian b xung gia

2 khung d liu hoc yu cu d liu trong trng hp mt trm b qu ti.

2.6. Nominal Bit Time:

Nominal BitTime l di ca mt bit trn bus. Mi nt trn bus phiiu chnh

nhp cngvi Nominal Bit Time c th pht vnhn chnh xcd liu trn bus.


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Hnh 2.22. Baudrate nh ngha thi gian cho 1 bit

Chun BOSCH mt thnh phn ca Nominal Bit Time,c chiara thnhnhiuon (segment):

- onng b (SYNC_SEG)

- on lan truyn (PROG_SEG)

- on pha buffer 1 (PHASE_SEG1)

- on pha buffer 2 (PHASE_SEG2)

Hnh 2.23: Mi bt c cu to bi 4 segmentsNominal Bit Time,tnhtheo giy, l nghcho ca dung lng trn bus:

2.7. S ng b xung clock

Mi nt phi to mt thi gian danh ngha BitTime cth nhn v phtd liu xung bus vi sng b cc ntkhc. Thc t, nu Nominal Bit Timeca


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mi nt khngcng b vi nhau, gi trc t bus ti thiim ly mu cth khng l gi tr ng vi thi im mong mun. tr ny c th lm nhhng trong nt nhn frame, khi m c t thi gian tnh ton CRC v gi 1 bitdominant trong ACKSlot xcnhn rng frameng.

Hnh 2.24: Vn ng b

2.7.1 SJW ( Synchronization Jump Width)SJKiu chnh mt bitclocki 1-4TQ (c khi to trc trong thanh ghi vkhngi trong qu trnh hotng) thc hin vicng b vi messagetruyn.

2.7.2 Li pha

PHASE_ERROR c pht hin khi s thay ibit dominant thnh recessive hay1 bit recessive thnhdominant khng xy ra bn trong segmentng b. Mt binec s dngnh gi li ny va ra tnhiu. S tnh tonec thc hinnh sau:

- e=0,khi s thayi bit xyra bn trong segmentng b (SYNC_SEG)- e>0, khi s thayi bitxy ratrc thiim ly mu

- e


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2.7.3 Cchng b

ng b cng (Hard Synchronization): ch xy ra khichuyn cnh bitutint recessive thnh dominant (logic1thnh 0) khibus rnh, bohiu 1Startof Frame (SOF).ng b cng lmcho bm bittiming khing li,gy nn mt chuyn cnh trong SyncSeg. Ti thiim ny, mi nt nhn sng b vi nt pht. ng b cng ch xy ra mt ln trong sut mt


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message.Vng b li cth khng xy ratrongcngmt bit (SOF) khimng b cngang xy ra.

ng b li (Resynchronization): c thc hin bo tonsng bthc hin bing b cng. Thiung b li, ntnhn khng th cc sng b v s lch phaca cc b daong ti mi nt.

S tnhton vmcng b lica rat gitr sais phae,v cng phthuc vo gitrSJW:

- Nu sai s pha e bng 0 (e=0, chuyn cnh trong Sync Seg), cch ng b li cng ging nhng b cng.

- Nu sais phaedng vb hn gi tr tuyti SJW(0


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2.8. Truyn nhn message

Hnh 2.25: S khi b nhn CAN message

Hnh 2.26: S khi b truyn CAN message

2.9. X l li

Khi truyn mt frame trn bus, li truyn cthnh hngn hotng ca ccnt trn bus.Li c thn t mtnt, lm cho mng khng cn hotng chnhxc, Vvy, nhiu cch pht hin lic s dng trong CAN

Ccloi li:

Bit Error:mi khi nt truyn gi mt bit xung bus, n kim traxem mcin


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p trnbusc ng vi bitcn gi haykhng. Nu khngng, n s bo hiubng mt Bit Error.

Tuy nhin, Bit Error s khng bo hiu trongnhng trng hp sau:- Khng c Bit Error noc tcng khimt bitdominantcgi trong vng ID thay th chomtbit recessive. Cng nh vy,trong vng ACK Slot, thay cho mt bit recessive.- Mt nt pht gi mt cli (bit recessive) v nhn bit dominant, ko

cn phi bo hiu Bit error. Li Stuffing( Stuff Error): Mt li Stuffingc pht hin trong

mi lnc 6 bit hay nhiu hn lin tc trnmtng dy ca BusTuy nhin, li Stuffing s khng botrong vng ID, vngiu khinv vng CRC.Cch Bit Stuffing khng p dng sau CRC. Trongmi trng hp, li Bit-Stuffing s khng bo trong on kt thcca frame hay trong vng ACK

Li CyclicRedundancy(CRC Error)Nu gi tr CRC tnh ton bi nt nhn khng ging vi gitr giibi nt pht, S cmt li CRC(CRCError).

Li ACK DelimiterMt li ACK Delimiterc bo khi nt nhn khng thy mt bit recessivetrong vngACK Delimiter hay trong vngCRC Delimiter.

Li Slot ACK (ACK Error)Mt li SlotACKc bobi ntpht khi nkhngc thy bit dominanttrong vng SlotACK.

Hnh tng hp nhng loi li khc nhau trong tng phn ca mt message frame

Hnh 2.27: Cc loi li khc nhau

2.10. CAN MODULE trn PIC

Controller Area Network (CAN) l modul thc hin cc chun giao tipCAN 2.0A hayBc nh ngha bi BOSCH. Modul h trCAN 1.2,CAN 2.0A, CAN 2.0B, CAN 2.0A, CAN 2.0 B Passive v CAN 2.0


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Active.

Module baogm:

- Thc hin cc giao thc CAN 1.2, CAN 2.0A v CAN 2.0B- H trcc loi Framechun vmrng- di d liu t 0-8 byte- Lp trnh tc ti 1Mbit/s- 2 buffer nhn vi hai buffer cha messagevi 2 mcu tin- 3 buffer truyn vi chu tin vkh nng b truyn.- Cc ngt doli truyn nhn.- Lp trnh xung clock.

2.10.1 Tng quan v module

Module baogm mt engine giao tip, cc buffermessage viu khin. Enginetng lmtt c cc chc nng nhn v truyn d liu. Messagec truynbngcch ghi vocc thanh ghitng ng. Trng thi vccli cth pht hinbngc cc thanhghitngng. Tt c ccmessage c kim trali v sosnh vi cc filter(thanh ghilc) xem ncc nhn vcha vo trong1 trong 2 thanh ghi nhn.


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Can h trcc kiu frame sau:-Kiu frame chun

-Kiu m rng- Remote frame-Errorframe- Overload Frame Reception-Khong giacc frame truyn

Cc ti nguyn trong module CAN:- 3 thanh ghi truyn: TXB0, TXB1 v TXB2- 2 thanh ghi nhn:RXB0 v RXB1-2mt n nhn(filter mask), mi cichomtthanh ghi nhn: RXM0,RXM1- 6 thanh ghi lc, 2cho RXB0 v 4 cho RXB1: RXF0, RXF1, RXF2,

RXF3, RXF4,RXF5.

Modul CAN s dng chn RB2/CANTX v RB3/CANRX giaotip vibus CAN. Trnh t sau thit lpCAN module trc khi s dngtruyn hay nhn:

1.m bo moduletrong ch thit lp2.Thit lp ch baud3.Thit lp cc thanhghilc vmt n4.a moduleCANv ch hot dng bnh thng hay ccchkhc ty theo p dng.


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2.10.2. Cc mode hot ng

1.Configurationmode:trong modeny, module CANc khi totrc khi hot ng. Modul CAN khng cho phpvomode ny khi cmts truyn haynhnang xy ra, n ging nh ci kha bo vcc thanh ghikhi hotng.

2.Listen mode: Mode ny dng quan st trng thi bus hay dng phn tch tc baud trongtrng hp cm nng.Cho vicphn tch tc Baud tng, cn thit phi c 2 nt giao tip vi nhau.

3. Loop back mode: mode ny cho php s truyn cc message tbuffer truyn sang buffer nhn m khng thc s truyn message ra ngoiCAN bus, s dng pht trin v kim tra h thng. Bit ACK khng ckim tra v thit b cho php cc messages t n nh nhng messagetccnt khc.

4.Disabledmode: trongmode ny, module khng truyn haynhn,Mode ny ging nh ttmodule, lm choxung clock dng.

5.Normalmode: lmodehot dng cho thit b. Trong modeny,thitb kim tra tt c cc message trn bus v to bit ACK, frame li v chl mode duy nht cho php truyn nhn messageln busCAN.

6. Error recognitionmode: modecth thit lp b quatt c ccli vnhn bt c messageno.

2.10.3. Truyn message CAN

a. Cc buffer truyn:

C3 buffer truyn TXB0, TXB1, TXB2. Mi buffer chim14 byte SRAMv bao gm mt thanh ghiiu khin(TXBnCON), 4thanh ghi ID (TXBnSIDL,TXBnSIDH, TXBnEIDL, TXBnEIDH), mt thanhghim did liu(TXBnDLC) v 8 thanh ghi d liu (TXBnDm).


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b.Thit lp truyn:

Bit TXREQ phic xa ch th bufferang rng hay messageva migii. Sau , cc thanh ghi SIDH,SIDL, DLC v thanh d liu c np. Nus dng frame m rng (ID m rng) th thanh ghi EIDH:EIDL phic ghi vbit EXIDEc set bohiu s dng framem rng.

btu truyn,ta set bitTXREQ chomi buffertruyn. truyn thnhcngth phi c t nht 1 node nhn bitc tc baudtrnmng.

Set bit TXREQ khng c ngha l truyn ngay, n ging nh bo hiu buffersn sng truyn. S truyn ch btu khi thit b kim trabus rnh. Sau thitb s truyn message no c mc u tin cao nht. Khi truyn thnh cng, bitTXREQ s xa, c TXBnIF c set v ngt s xy ra nu bit cho php ngtTXBnIEc set.

Nu truyn khng thnh cng, bit TXREQ vn c set, bo hiumessage vn cha gii quyt (pending) v mt trong cc c s set. Nu c li,TXERRv IRXIFs setv mt ngt s sy ra. Nu message mtutin trn bus, bit

TXLARB s set.c.u tin truyn:

Su tin ny khng lin quanti su tin ca messagetrnbus theo giaothc CAN. y ch l s u tin trong thit b xem message no s c truyntrc hay th t truyn ca 3buffer. Buffer no c mc u tin cao nht s ctruyn trc . Nu 2 buffer c cng mc u tin, th buffer no cs k hiu caohn sc truyn trc. C 4mcu tin: nucc bitTXP l 11, th buffer cmcutin cao nht; nu cc bitTXP l 00, th buffer cmcu tin thp nht


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2.10.4. Nhn message:

a. Cc buffer nhn:

C 2 buffer nhn RXB0v RXB1.Mi buffer chim14 byte SRAM v baogm mt thanh ghi iu khin(RXBnCON), 4 thanh ghi ID (RXBnSIDL,RXBnSIDH, RXBnEIDL, RXBnEIDH), mt thanh ghi m di d liu(RXBnDLC) v 8 thanh ghid liu (RXBnDm).

N cn c mt buffer ring Message Assembly Buffer (MAB) c vai tr lmt buffer ph. MAB lun nhn messagek tip trnbus v khng th tcng trctip bi firmware. Buffer MAB tip nhn ln lt tt c cc message ti. Massagesauc truyn ti buffer nhn tngng ch khi no ID ca messageng vib lc.

b.Nhn mt message:

Hnh 2.28: Cc bufer nhn

Cho tt c cc buffer, MAB (message assembly buffer) c s dng nhn message k tip trn bus. MCU c th tc ng mt buffer trong khi bufferkia nhnmessage hay gi message va nhn.

Khi mt message chuyn ti bt k buffer nhn no bit RXFUL c set.Bit ny phi c xa bi MCU khi n x l xong message trong buffer cho php message mi c th nhn trong buffer. Bit nym bo thit b x lxongmessage trc khi module c gnga message mi vo buffernhn. Nu mtngt nhn cho php, th ngt s xy ra bo hiu mt message c nhn thnhcng.

Khimessagecavo thanhghi nhn, phn mm cth xcnhchnhxc b lc no cho php s nhn ny bng cch kim tra filter hit bitsFILHIT trong thanh ghi RXBnCON tngng. Messageva nhn lmessafe


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chun nu bit EXID trong thanh ghi RXBnSIDL c xa. Ngc li, bit EXIDc set s bohiu mt messagem rng.

c.u tin nhn

RXB0 l buffer c mc u tin cao nht v c hai b lc kt hp vi n.RXB1 lbuffer c mcu tinthp v c4b lc. Hn na, thanhghi RXB0CONc th thit lp khi RXB0 cha mt message hp l, v mt message hp lkhc khi c nhn, mt error s khng xy ra v message mi sca voRXB1. C 2mt n lc chomi bufer.

Hnh2.29: RXB0 cha mt message hp l, message khc khi c nhn sca vo RXB1

d. MessageAcceptanceFiltes and Masks.c s dng xcnh xemmessagetrongMAB cc chuyn vocc

bufer nhn hay khng. Khi mt messgehp l va c nhn vo MAB, vng IDc so snh vi gi tr ca b lc. Nung, messagesc chuyn vo bufertngng. Filtermaskc s dng xcnh xem bit no trong vng ID scso snh vi b lc. Bng chntr cho thy mi bittrong IDc so snh vi mt nvb lc xcnh message cc chuyn vobuffernhn haykhng.Nu bitnoc thit lp bng 0,bit sc chp nhnm khng cn xtn b lc.


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2.10.5. Baud Rate Setting:

TimeQuantumc tnhtheo cng thc:

trong FOSC ltn s xung clock, TOSC l chu k daong v BRP l s nguyn(t 0n 63) theo gi trcc bit BRGCON1.

2.11. Gii thiu mt s chip CAN thng dng v ng dng trong thc t

Tu phc tp, yu cu ca mng m chn CAN controller. n gin th chnSJA1000, 81C90/81C91, 82C200,.. y l dng Stand-alone CAN controller. Phc tphn th chn cc h Vi iu khin c tch hp CAN 2.0B: H 8051: Infineon C505C,C515C, Philips 8xC592, 8xC592, 8xCE598, Atmel T89C01CC01, CC02, CC03. HC16: Infineon C167CR, C164CI. H AVR: AT90CAN128. H PIC: PIC18C658,PIC18C858, PIC18F248,... v.v v v.v.

K n th chn tip CAN interface tranceiver MCP2551, PCA82C250, PCA82C251,CF150, MAX3059, MAX3059...

Tham kho s ng dng ca tng con chn m bit cch kt ni chng li vinhau v kt ni vo CAN bus. Yu cu cn bao nhiu node th thit k by nhiu.


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2.11.1. Mch ng dng tham kho:

Hinh2.30: Mch Tham Khao PIC tch hp CAN

2.11.2. Mch giao tip CAN:


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Hinh2.31: Mch Tham Khao PIC tch hp CAN

Xong ri th vit chng trnh mng CAN cho cc node giao tip vi nhau.Tiliu tham kho:http://canopen.sourceforge.net

http://canfestival.sourceforge.net

http://www.can-cia.org


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2.11.3 Kt ni mng CAN vi cc MCU

Hinh2.32: Kt ni mng CAN vi MCU



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Cp v mc bo v

V bn cht, c mt s im khc bit c bn gia mi trng ng dng ca t

v mi trng cng nghip m cc nh thit k cng nghip cn cn nhc khi la chn

v ng dng cng ngh CAN. Trong nhiu ng dng t vn an ton khng c

cao th thng cn ng truyn d liu CAN di 500 kbp ch khng nht thit phi

c tc trn 1Mbp nh nhiu ng dng cng nghip. Ngoi ra, cp trn sn my cng

nghip ng nhin phi di hn so vi s dng trong cc phng tin i li mc d tc

d liu lun t l nghch vi chiu di cp..

di cp nh hng n tc truyn thng CAN

Chiu di ng cp (m) Tc tn hiu (kbps)

30 1,000

100 500

250 250


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500 125

1,000 62.5

Thm vo , cp di hn thng chu nh hng ca in t cao nn tnh nng

chng nhiu l rt quan trng. y chnh l mi trng m nhng nh sn xut cht bn

dn ang tp trung pht trin cng ngh CAN cng nghip ca h.

Tng vt l l mt trong nhng thnh phn quan trng nht ca mng CAN bi v

n l yu t cn thit to ra hiu nng mnh m. Trong nhng ng dng cng nghip,

tng vt l c nh theo chun ISO 11898-2, c tc trn 1Mbp. Tiu chun ny xc

nh chc nng thit b truy cp truyn thng (MAU) v mt s c tnh giao din ph

thuc truyn thng (MDI). thc hin cc chc nng tng vt l cn n mt mch thupht CAN ni ti bus 2 dy:

Trong nhng nm gn y, loi mch ny c tch hp vo cc IC gim

lng linh kin v n gin qu trnh sn xut. Mt s cng ty ln sn xut nhng thit

b ny nh Texas Instruments, Infinion, Phillips, Microchip v AMIS. Hnh 12.1 l biu

khi ca thit b thu pht CAN tc cao, tun theo AMIS-30660, c chng nhn

Vd1.1 v tng thch vi ISO 11898-2. Nm trong mt gi SO-8, gii php n chip(single-chip) ca IC cung cp kh nng truyn vi sai ti bus CAN vt l v kh nng

nhn vi sai ti b iu khin giao thc CAN ng thi cung cp cc cp bo v cao

chng li s ngng nht thi (transients) trong nhng mi trng cng nghip.


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Gim tc nhn gy nhiu

Nhng thit b CAN i mi c nhiu li th hn so vi cc IC thu pht c, c

bit l kh nng chng li cm in t (EMS), sng in t (EME) v s phng in

tnh (ESD). Trong nhiu trng hp, nhng tc nhn ny c th gy ra mt lin lc gia

cc bus.

Kh nng kh in t (EMI) cng phi c cn nhc khi chn mt my thu pht

CAN. Chip thu pht CAN c thit k hon hoc thc hin trong mt b cc i xng

vi vic sp xp thi gian truyn tn hiu ti dch chuyn 180o m vn gi tr khng

bn trong chip mc nh nht.

Thm vo , cc chip CAN c thit k loi tr ch chung CMR

(common-mode rejection). Nguyn nhn gy ra ting n CMR l s khc nhau v in

th gia tip t ca nt gi v nt nhn trn CAN. Ting n ny thu c t nh sng

hunh quang hay thit b chuyn mch in nh cp ngun v ng c. Hu ht cc my

thu pht CAN u c mt di CMR t -2V ti +7V cho cc u vo b thu.

Nh ng dng cc k thut thit k, cc nh sn xut chip c th n gin ha

vic thc hin tnh nng tng vt l ca CAN bng cch loi tr vic s dng cun cm

khng common-mode vic sp xp n gin hn v gim chi ph vt liu.Mc tch hp cp h thng

Vic s dng cng ngh bn dn cao p, tn hiu hn hp cho php cc k s t

c cc mc tch hp h thng cao hn v gip h to ra gii php h thng ASIC

chnh xc. Chng hn nh, my thu pht CAN v b iu khin c th c kt hp

trong mt IC gim s lng linh kin ca cc nt CAN. Tch hp mc cao hn c

ngha l kch c mch nh hn, tit kim khng gian v m ra nhng kh nng mi c

th bao gm vic tch hp my thu pht CAN v tnh nng iu khin trc tip vo mt

giao din cm bin, cn tc ng, ng c hay b sung nhng chc nng mi m khng

tn khng gian mch.

Chun ISO 11898 da trn mt bus c chiu di 40m vi mt nhnh m rng

0.3m. Khong cch ny c th c m rng nh mt my thu pht CAN thit k hon


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ho. Thc t, hai bus c th ni vi nhau bng cch ch n mt b lp CAN 1 chip AMIS-

42700 vo gia CAN-L v CAN-H. B lp CAN 1 chip gip nh thit k mng CAN

n gin ha vic m rng chiu di bus v cho php h pht trin mt nt n gin cho

cc ng dng kt ni-ngng kt ni.

Cc giao din CAN tch hp, thu nh ngy cng c mt vai tr quan trng khi cc

cm bin ngy cng nh hn ph hp vi nhng ng dng mi. Li ch ca vic kt

hp mt my thu pht CAN v mt b iu khin trn mt chip to ra tin cy cao,

khng cn kim tra nhiu v gim s lng linh kin phc tp t hai xung cn mt.

Tm li, phi ghi nhn rng nn tng ca CAN trong ngnh cng nghip t m ccho cc nh thit k xm nhp ti nhiu cng c v dch v ca bn th ba c kh nngpht trin v h tr cc ng dng da trn CAN. Trong c cc cng c miu t v cuhnh mng CAN cp cao; cng c v dch v chun ha chn on d liu v giaotip; cc cng c o lng v nh chnh.

2.12. u im ca CAN* Tiu chun hon chnh.-Giao thc CAN c hn 14 nm pht trin-C nhiu sn phm v cng c v CAN trn th trng*.Phn cng (tng vt l) h tr y cho giao thc (protocol)-Kt hp gia x l v giam li vi truyn tc cao (max 1Mbps-at 40m, 50kbps at1km).

*.Phng tin truyn n gin-Chun l dy xon, nhng vi dy thng th vn chy tt.-Trn cc kiu truyn khc: quang, v tuyn.*.X l li tt-y l mt im mnh ca giao thc ny: c ch d li m rng.*.Giam li mnh.-Gip ngn nga nt mng hng nh hng n ton h thng.*.Giao thc c dng hu ht trong cng nghip v t ng.*.Hiu nng Gi c tt.

2.13. Hng CAN open

c im:-CANopen l mt nhm nh ca CAL (CAN application layer) c CiA pht trin.-T ng cu hnh mng-D dng truy cp tt c cc thng s thit b-ng b ho thit b-Truyn ti d liu theo chu k v s kin-c hoc ghi cc thng s vo ra mt cch ng bng dng:-My t ng


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Thun li:-D dng tch hp cc cm bin v c cu truyn ng u t rt nh-M v cc nh pht trin c lp-H tr cc thit b khc-Kh nng tc cao thi gian thc


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CHNG III

SO SNH CAN VI CC MNG TRUYN THNG KHC

3.1.Chun RS-232

cc thit b thu pht c th lm vic c hiu qu v khng gp rc ri khi lm vicphi hp, t lu ngi ta t ra cc tiu chun cho cc cng vo/ra tn hiu tun ttrong cc thit b s. l tiu chun RS-232, vi cc gic cm ch D dao ng t 4n 37 chn (4, 9, 15, 37 chn).RS-232 (tng ng vi chun chu u l CCITT V.24) c dng ch yu trong vicgiao tip im - im gia hai thit b u cui (DTE), v d gia hai my tnh, giamy tnh v my in, hoc gia DT v mt DCE- thit b giao tip d liu, v d gia mtmy tnh v mem.RS 232 s dng phng thc truyn thng khng i xng, tc l s dng tn hiu inp chnh lch gia mt 3V. Bt kdy dn v t. Cc cng ca RS - 232 c ngngin p qui c l tn hiu c p ln +3V c coi c logic 0 hoc c gi tr thp (L) ,cn tn hiu c p nh hn 3V c coi c logic 1 hoc gi tr cao (H). in p gia3V khng c ngha.Chnh v t - 3V ti 3V l phm vi khng c nh ngha, trong trng hp thay igi tr logic t 0 ln 1 hoc t 1 xung 0 mt tn hiu phi vt qua qung qu trongmt th gian ngn hp l. iu ny dn n vic phi hn ch v in dung ca ccthit b tham gia v ca c ng truyn. Tc truyn dn ti a ph thuc vo chiudi ca dy dn. a s cc h thng hin nay ch h tr vi tc 19,2 kBd (chiu dicho php 30 50 m).

Ch lm vic ca h thng RS 232 l hai chiu ton phn (full-duplex), tc l haithit b tham gia c th thu v pht cng mt lc. Nh vy vic thc hin truyn thngcn ti thiu 3 dy dn - tring hai dy tn hiu ni cho vi cc u thu pht ca haitrm v mt dy t. Vi cu hnh ti thiu ny, vic m bo an ton truyn dnthuc v trch nhim ca phn mm. RS 232 c mt u im l c th s dng cngsutpht tng i thp, nh tr khng u .vo hn ch trong phm vi t 3-7kTrong cc Rle s thng dng loi gic cm 9 chn v loi 25 chn. Chun RS-232 quinh mc p, tc truyn v chc nng cc chn ca gic cm. Trn bng sau trnh bys v cc chc nng cc chn ca loi 9 chn v 25 chn

Chn( Loai 9 chn) Chn( Loai 25 chn) Chc nng1 8 DCD - DCD - Data Carier Detect Li ra2 3 RxD - Receive Data Li vao3 2 TxD - Transmit Data Li ra4 20 DTR - Data Terminal Ready Li ra5 7 GND - Ni t6 6 DSR - Data Set Ready Li vao


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7 4 RTS - Request to Send Li ra8 5 CTS - Clear to send Li vao9 22 RI - Ring Indicator Li vao

UART v Np Chng Trnh Mch RS232

Hinh 3.1 UART v Np Chng Trnh Mch RS232

* UART(universal asynchronous receiver/transmitter) l mt giao thc truyn nhnbt ng b c s dng kt ni my tnh vi cc thit b khc qua chun EIARS-232

* Cch thc truyn nhn ca UART

3.2.RS 485.

Hin nay, truyn tn hiu i xa hn v ni vi nhiu thit b u cui hn, ngi tadng chun RS-485 tng t RS232 nhng c mc in p tn hiu cao hn. s dng


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chun ny, ngi ta c cc b chuyn i tn hiu chun t RS-232 thnh tn hiu chunRS-485.

Ngng gii hn in p qui nh cho RS 485 c ni rng ra khong 7V n 12V,v tr khng u vo cng c tng ln. Ngoi kh nng ging nh RS 232, RS-485cn c kh nng ghp ni nhiu im , v th c dng ph bin trong cc h thngbus. C th, 32 trm c th ghp ni, c nh a ch v giao tip ng thi trong mt

on RS-485 m khng cn b lp. t c iu ny, trong mt thi im ch mt trm c php kim sot ng dnv pht tn hiu, v th mt b kch thch u phi a v trangh thi tr khng cao mikhi ri, to iu kin cho cc b kch thch cc trm khc tham gia. Ch ny cgi l tri-state. mt s vi mch RS-485 t ng x l tnh hung ny, trong nhiu trnghp kc vic thuc v trch nhim ca phn mm iu khin truyn. Trong mch cab kch thch RS-485 c mt tn hiu u vo Enable c dng cho mc chchuyn b kch thch v trng thi pht tn hiu hoc tri-state.Mc d phm vi lm vic ti a t 6V n 6V trong trng hp h mch, trng thilogic ca tn 5V i vi u ra (bn pht)1,5V n hiu ch c nh ngha trongkhong t 5V i vi u vo (bn thu).0,2V n v tRS-485 cho php ni 32 trm, ng vi 32 b thu pht hoc nhiu hn, tu theo cchchn ti cho tng thit b thnh vin. Gii hn ny xut pht t c tnh k thut ca hthng truyn ti nhiu im. Cc trm c mc song song v th vic tng s trm slm suy gim tn hiu vt qu mc cho php.

Tc truyn ti v chiu di dy dn

RS-485 cho php khong cch ti a gi trm u v trm cui trong mt on mng l1200m, khng ph thuc vo s trm tham gia. Tc truyn dn c th ln n 10Mbit/s, mt s h thng gn y c th ln n tc 12 Mbit/s. Tuy nhin c s traoi gia tc truyn dn ti a v di dy dn cho php, tc l mt mng di1200m khng th lm vic vi tc 10Mbd. Quan h gia chng ph thuc rt nhiuvo vic nh gi cht lng tn hiu.

3.3 . I2C S Khi

Hnh 3.2 I2C

c im

- Giao tip bus tng thch vi I2C Fast chun. 7 bit a ch- D dng thit lp Ch, T hoc Ch/T- Xung clock c th lp trnh cho php iu khin tc linh hot


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- Truyn dn song phng gia Ch v T

Cu Trc Byte u Tin

Cu Trc D Liu

LSB ACK

7-bit a ch ca slave

R/W :0 Slave s c ghi bi Master.

1 Slave s c c bi Master.

R/W

MSB

S SLAVE ADDRESS W A DATA A DATA A P

Master Write:

Master Read:

ACK t Master

ACK t Master

Khng ACK t Master

S SLAVE ADDRESS R A DATA A DATA NA P

ACK t Slave


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3.4. im khc bit c bn cua CAN v cc mng truyn thng khc

- L CAN l mt pht trin chung ca hai hng BOSCH v INTEL phc v vicni mng trong cc phng tin giao thng c gii thay i cch ni im im cin, chiu di dy dn c th ln ti vi kilomet, khi lng c th len vi kilogam vtc truyn dn tng i cao.

- CAN l phng php nh a ch v giao tip hng i tng, trong khi hu

ht cc h thng bus thng khc u giao tip da vo a ch cc trm.Mi thng tintrao i trong mng c coi nh mt i tng , c gn mt m s cn cc .Thngtin c gi trn bus theo kiu truyn thng bo vi di c th khc nhau.

Cc thng bo khng c gi ti mt a ch nht nh m bt c trm no cngc th nhn theo nhu cu.Ni dung mi thng bo c cc trm phn bit qua mt mcn cc ( IDENTIFIER).M cn cc khng ni ln a ch ch ca thng bo, mch biu din ngha ca d liu trong thng bo.V th, mi trm trn mng c th tquyt nh tip nhn v x l thng bo hay khng tip nhn thng bo qua phng thclc thng bo(message filtering).Cng nh x dng phng thc lc thng bo, nhiutrm c th ng thi nhn cng mt thng bo v c cc phn ng khc nhau.

Mt trm c th yu cu mt trm khc gi d liu bng cch gi 1 khungREMOTE FRAME.Trm c kh nng cung cp ni dung thng tin s gi tr li mtkhung d liu DATA FRAME c cng m cn cc vi khung yu cu.Bn cnh tnhnng n gin, c ch giao tip hng i tng CAN cn mang li tnh linh hot vtnh nht qun d liu ca h thng.Mt trm CAN khng cn bit thng tin cu hnhh thng ( v d a ch trm), nn vic b sung hay b i mt trm trong mng khngi hi bt c mt s thay i no v phn cng hay phn mm cc trm khc.Trongmt mng CAN , c th chc chn rng mt thng bo hoc c tt c cc trm quantm tip nhn ng thi, hoc khng c trm no tip nhn.tnh nht qun d liuc m bo qua cc phng php gi ng lot v x l li.


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CHNG IV

GII THIU MCH THI CNG NG DNG

4.1. S nguyn l:Dng PIC18F458 o nhit t LM35 v hin th nhit ra mn hnh LCD,

thng qua kt ni mng CAN.4.1.1 Mch PIC:


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Hnh 4.1 Mch PIC

4.1.2 Mch o nhit :

Hnh 4.2 Mch o nhit

4.1.3 Mch hin th nhit ra LCD:

Hnh 4.3 Mch hin th nhit ra LCD


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4.2 Trnh bin dch CCS:

Hnh 4.4 trnh bin dich CCS


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4.3. Chng trinh nap dnh cho PIC:

Hinh 4.5 Chng trnh np dng cho PIC


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TI LIU THAM KHO:

1. Mng truyn thng cng nghip Hong Minh Sn,NXB Khoa hc v ki thut.

2. http://www.diendandientu.com3. http://vagam.net4. http://canopen.sourceforge.net

5. http://canfestival.sourceforge.net

6. http://www.can-cia.org

Documents

CAN.tri 05111106. Noi Dung Bao Cao