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  1. #1
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    canbus canh canl

    Hello!

    I want to connect two High Speed CAN transceivers (MCP2551) but I donít 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 transceiverís datasheet and they donít mention those resistors).

    Thanks a lot in advance for your help!

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    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.



    •   Alt5th December 2007, 18:53

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  3. #3
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    can bus shielding

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



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    db9 can bus pinout

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



    •   Alt20th December 2007, 11:36

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    can bus canh

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



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    can bus shield termination

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



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    canh canl

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



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    can canh canl

    Quote Originally Posted by funnynypd
    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.



  9. #9
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    how to connect can bus

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



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