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CANH and CANL in CAN Bus

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alefandra

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canbus canh canl

Hello!

I want to connect two High Speed CAN transceivers (MCP2551) but I don’t know exactly how to do it. Is it enough to link the CANH and CANL pins of the transceivers or do I have to link also the grounds? What connector is the most suitable? Is a DB9 ok? Do I have to terminate the bus with a termination resistor at both ends of the bus in order to avoid reflections? Or are those resistors included in the transceiver? (I read the transceiver’s datasheet and they don’t mention those resistors).

Thanks a lot in advance for your help!
 

canl can low canh

CAN uses a DB9 as standard.
Here are the pinouts.

9 Pin (male) D-Sub CANbus PinOut Pin # Signal Names Signal Description

1 Reserved Upgrade Path
2 CAN_L Dominant Low
3 CAN_GND Ground
4 Reserved Upgrade Path
5 CAN_SHLD Shield, Optional
6 GND Ground, Optional
7 CAN_H Dominant High
8 Reserved Upgrade Path
9 CAN_V+ Power, Optional

You dont have to connect the grounds, just can high and can low.
Each end of the bus must be terminated with a 120R resistor.
They are not in the tranceiver as the tranceiver might not be at the end of the bus.
 

can bus shielding

Thank you so much btbass! You told me everything I needed to know!
 

db9 can bus pinout

If the two equipment have power supply you can connect only CANH and CANL.
 

can bus canh

It depends on which protocol you are going to use, some protocol has a definition of connectors.
 

can bus shield termination

If 2 system using one ground, it is not needed to connect ground, otherwise you should connect ground signal.
 

canh canl

can is differential signal net, no ground required.
A gnd shield will help for emi purpose.
 

can canh canl

funnynypd said:
can is differential signal net, no ground required.
A gnd shield will help for emi purpose.

If two node are galvanically isolated , it may no problem.
Otherwise differential ground voltage on 2 node must limited. so it is better to cannect ground signal.
 

how to connect can bus

true,
For vehicle has the same ground, a two wire network will also work.
 

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