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SN65HVD232: communication instability

Zhonghui Xu
Expert 5445 points
Part Number: SN65HVD232

Hi team,

SN65HVD232D access can network, communication instability (A and B communication interaction, ask and answer, sometimes drop frame).

Both sides add 120ohm matching resistor, 500K communication rate.


Please help to analyze it,

Thanks.

Best regards,

  • 0
    TI__Genius 15345 points

    Hello,

    Do you have any scope shots of the issue? Specifically it would be good to see the CANH and CANL lines, the VCC, and the TXD pin when an error occurs.

    Also what voltage are you powering this device with? I see you have one 120 ohm termination resistor on the device in the schematic you attached. Just to confirm the other CAN device on your bus also has a 120 ohm termination resistor right?

    Best,

    Chris

  • 0 in reply to Chris Ayoub
    TI__Expert 5445 points

    Hi Chris,

    Thank for your reply.

    The main problem is that communication instability.

    3.3V power supply, can transceiver circuits on both sides and can waveform at the fault time (not necessarily the waveform at abnormal time)

    Best regards,

  • 0 in reply to Zhonghui Xu
    TI__Genius 15345 points

    Hi Zhonghui,

    Can you share the full CAN frame sent by the SN65HVD232? Also can you verify the voltage on the VCC input. The CANH line seems a little high to be supplied with a 3.3V voltage supply.

    Best,

    Chris

  • 0 in reply to Chris Ayoub
    TI__Expert 5445 points

    Hi Chris,

    Thank for your reply.

    please check the picture.

    Best regards,

  • 0 in reply to Zhonghui Xu
    TI__Guru 50835 points

    Hi Zhonghui,

    Both of these waveforms (from the 5V transceiver initially and the 3.3V transceiver) look very good. I don't expect any waveform like these to be misinterpreted by the receiving transceivers in this network. Additionally it sounds like the system is properly terminated and simple in topology (point to point). Based on this information, if conditions do not change, it doesn't seem like this issue is hardware related. 

    • What is the frequency that the system drops a frame? Is it a measurable percentage, or does it only happen occasionally?
    • Are the conditions that cause a dropped frame recreatable?
    • Have you identified anything that increases/decreases the frequency of the failure?
    • Are there any sources of noise near the test setup? Switching power supplies, motors, etc.
    • Are the CAN controllers in the system reporting any specific errors when a dropped frame occurs? Generally they will be able to recognize which portion of the communication failed (CRC, arbitration error, missing ACK, etc.). 

    Regards,
    Eric Schott