使用MCP2515的PIC16F876的智能传感器CAN节点

Advancesindatacommunicationshavecreated

efficientmethodsforseveraldevicestocommunicate

overaminimumnumberofsystemwires.The

ControllerAreaNetwork(CAN)isoneofthese

methods.CANsendsandreceivesmessagesovera

two-wireCANbus.Thenodesbroadcasttheir

individualmessagesovertheCANbus.Meanwhile,the

receiversaresetuptoacceptthemessageand

anticipateanAcknowledgment(ACK)signal,indicating

thereceiptofanon-corruptedmessage.Theprotocol

oftheCANhastwostatesandthebitsareeither

dominant(logic‘0’)orrecessive(logic‘1’).Nodesmay

attempttotransmitamessageatthesametime.To

ensurethatcollisionsdonotreducethethroughputof

thebus,thereisanarbitrationscheme.Inthisscheme,

anodewillcontinuetotransmituntiladominantbitis

detected,whilethatnodeisexpectingarecessivebit

(intheIDfield)ontheCANbus.Thenode(s)thatlost

arbitrationwillautomaticallyterminatetheirtransmis-

sionandswitchtoReceivemode.AftertheCANbus

entersanIdlestate,thesenodesattempttoretransmit.

Ifthenodedidnotlosearbitration,itcompletesits

transmission.(ForadditionalinformationontheCAN

protocol,refertoAN713,“ControllerAreaNetwork

(CAN)Basics”,DS00713.)

Thebusconfigurationoperatesbythemulti-master

principle,andallowsseveralNodeBoardstoconnect

directlytothebus.IfoneNodeBoardfailsinthe

system,theotherNodeBoardsarenotaffected.The

probabilityoftheentirenetworkfailingisextremelylow

comparedtoringtypenetworks.Ringtypenetworks

haveahighprobabilityfailurerate,duetothefactthat

ifonenodemalfunctions,theentirenetworkbecomes

inoperable.TheCANcontrollerseekstosolvethis

problem.AN212SmartSensorCANNodeUsingtheMCP2515andPIC16F876MODULEOVERVIEWAuthor:MikeStanczykDiversifiedEngineering,Inc.Themodulehardwarecanbedividedintotwocomponents.Theseare:CAN-NETNodeBoardINTRODUCTIONCAN-NETAnalogInputBoardAdvancesindatacommunicationshavecreatedTheseboardscanbepurchasedfromDiversifiedefficientmethodsforseveraldevicestocommunicateEng