end to end information about canbus

8/18/2019 End to End Information about CANBUS

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Introduction to

CANBUS

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1. CANBUS Introduction

What is CANBUS? Who uses CANBUS?

CANBUS history

CANBUS timeline

2. CANBUS Characteristics OSI Model

Physical ayer

!ransmission Characteristics

". Messa#e Oriented Communication

$. Messa#e %ormat&. Bus Ar'itration

Presentation Goals

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CANBUS or CAN 'us ) Controller Area Net*or+ bus

An automoti,e serial 'us system de,elo-ed to satisy

the ollo*in# re/uirements0

Net*or+ multi-le microcontrollers *ith 1 -air o *ires.

Allo* microcontrollers communicate *ith each other.

i#h s-eed real3time communication.

Pro,ide noise immunity in an electrically noisy

en,ironment.

o* cost

What is CANBUS?

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4esi#ned s-eci5cally or automoti,e a--lications !oday 3 industrial automation 6 medical e/ui-ment

Who uses CANBUS?

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Automoti,e Medical 6 Industrial

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CANBUS History

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%irst idea 3 !he idea o CAN *as 5rst concei,ed 'yen#ineers at =o'ert Bosch >m'h in >ermany inthe early 1


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CANBUS Timeline

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CAN is a closed net*or+◦ ) no need or security sessions or lo#ins.

◦ 3 no user interace re/uirements.

Physical and 4ata in+ layers in silicon.

CANBUS and the S! Model

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CANBUS Physi"al #ayer

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Conventional multi-wire looms CAN bus network

Physical medium ) t*o *ires terminated at 'oth ends 'y resistors.

4iDerential si#nal 3 'etter noise immunity.

Bene5ts0 =educed *ei#ht =educed cost

%e*er *ires E Increased relia'ility

vs.

http://canbuskit.com/what.php


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Transmission Chara"teristi"s

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U- to 1 M'it6sec. Common 'aud rates0 1 M &77 F and 12&

F All nodes ) same 'aud rate MaG len#th0127H to 1&777H @rate de-endent

© esd eect!onics" #nc. $ 525 %e!na!dston &oad $ '!een(ied" )* +13+1


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Messa$e riented Transmission Proto"ol

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ach node ) recei,er transmitter A sender o inormation transmits to all de,ices on the 'us

All nodes read messa#e then decide i it is rele,ant to them All nodes ,eriy rece-tion *as error3ree All nodes ac+no*led#e rece-tion

CAN bus© 2++5 )ic!ochip ,echnoo- #nco!po!ated. * &i-hts &ese!ved.


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Messa$e %ormat

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ach messa#e has an I4 4ata and o,erhead.

4ata ); 'ytes maG O,erhead ) start end C=C ACF


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&'am(le o) Messa$e Transa"tion

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Bus Arbitration

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Ar'itration ) needed *hen multi-le nodes try to transmit atthe same time

Only one transmitter is allo*ed to transmit at a time. A node *aits or 'us to 'ecome idle Nodes *ith more im-ortant messa#es continue transmittin#

CAN bus© 2++5 )ic!ochip ,echnoo- #nco!po!ated. * &i-hts &ese!ved.


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Bus Arbitration

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Messa#e im-ortance is encoded in messa#e I4.

o*er ,alue E More im-ortant As a node transmits each 'it it ,eri5es that it sees

the same 'it ,alue on the 'us that it transmitted. A J7K on the 'us *ins o,er a J1K on the 'us.

osin# node sto-s transmittin# *inner continues.


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CAN 'us ) Controller Area Net*or+ 'us Primarily used or 'uildin# CU net*or+s in

automoti,e a--lications.

!*o *ires OSI 3 Physical and 4ata lin+ layers 4iDerential si#nal 3 noise immunity 1M'it6s 127H

Messa#es contain u- to ; 'ytes o data

Summary

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Mare+ ae+

&nd o) Presentation

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A J7K @lo* ,olta#e on the 'us 'y 1 node

*ins o,er a J1K @hi#h ,olta#e on the 'us.

Bus arbitration

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Bus Arbitration %lo*"hart

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