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  1. #1
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    How to check CAN line ??

    Hello,

    How to check CAN communication line weakness??

    In my system my one device is communicate to several controllers via CAN communication. suddenly one of my CAN device is stop responding and does not communicate with master CAN controller.

    For verification purpose i have connect my master controller to other system where i got the same issue.

    After searching on internet i found that in CAN communication weak signal causes the issue. May few device will communicate and some of may not.

    Can anybody know how to test CAN line??

    •   Alt20th December 2016, 17:25

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  2. #2
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    Re: How to check CAN line ??

    waveform is attached for reference.


    Please answer someone



    •   Alt21st December 2016, 17:14

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  3. #3
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    Re: How to check CAN line weakness

    For verification purpose i have connect my master controller to other system where i got the same issue.
    So you suspect the master controller is sending weak signal.

    In the CAN network most of the signal current pass through the bus termination resistors. So if you increase the value of the termination resistors then the signal voltage level will increase and the system may work.
    Usually termination resistors are 120 ohms. Try with 180 ohms. Due to increased termination resistance, reflection related problem will increase but may not too much. See what happens.



    •   Alt21st December 2016, 19:35

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  4. #4
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    Re: How to check CAN line weakness

    You are making a rookie mistake when viewing the CAN waveforms on a scope.

    The grounds (arrows 1 and 2) should both be aligned.
    CANH will automatically sit on the top, and CANL on the bottom.

    Then, and only then will you see if you meet the CANBus voltage requirements for recessive and dominant states. Which include not only min and max voltage values, but the differential values too.
    Google CANBus for the valid voltage value range.

    Use the automatic measurements correctly too.........Use Ch1 max, Ch1 min, Ch2 max and Ch2 min. Remove any RMS measurements....those are meaningless.
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