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SN65HVD1050-Q1: Frame errors on nodes

Valentinas Pancerovas
Intellectual 410 points
Part Number: SN65HVD1050-Q1
Other Parts Discussed in Thread: TCAN1057A-Q1

Hello,

Our customer is having problems with their nodes. When they hook up our device, it causes frame errors on their nodes because of our noisy PCB injecting the noise into the CAN bus.

If the noise is common mode, it should not cause any frame errors, am i correct?

Could it be that their transceiver is not good enough at rejecting the CM noise?

Could it be that the ground shift is too high? We have isolated systems so the ground does shift. 

Why do oscilloscopes use only H or L for decoding and triggering CAN errors when the actual use case is using the differential signal? We are using Kvaser to communicate to our PC and we get 0 CAN errors, so how come our customer is having issues on their nodes?

Please let me know what other information i should provide, if that helps.

Thank you,

Valentinas 

  • 0
    TI__Mastermind 26746 points

    Valentinas,

    Thanks for reaching out. Usually when troubleshooting CAN communication, you can get an idea of what's going on by looking at the waveform shapes across the bus, particularly where you're seeing the errors arise. The most useful observations of CAN communication usually involve showing CANH, CANL, TXD, and RXD on the same image.

    It's possible that this could be fixed by using the recommended newer component TCAN1057A-Q1 which has higher performance.

    Valentinas Pancerovas said:
    If the noise is common mode, it should not cause any frame errors, am i correct?

    Yes, for the most part. Keep in mind that transceivers do have a common-mode range limitation. Many transceivers limit common-mode range to ±12 V. Not sure how much common-mode offset you're expecting. Let me know if you can get an estimate (maybe on a multimeter).

    Valentinas Pancerovas said:
    When they hook up our device, it causes frame errors on their nodes

    Do you know the original error? When one node experiences an error and transmits an error frame, it causes every other node on the network to detect a stuffing error. One way to track down the troublesome node(s) is to see in the traffic log which devices are experiencing different errors. This digital analysis could complement analog analysis (see oscilloscope comment above) to figure out what's going on.

    Valentinas Pancerovas said:
    Why do oscilloscopes use only H or L for decoding and triggering CAN errors when the actual use case is using the differential signal?

    I can't speak for the oscilloscope manufacturers. Slight smile I know that on the occasions I use protocol-aware oscilloscopes, it usually just uses VD (i.e. VCANH - VCANL).

    Valentinas Pancerovas said:
    We are using Kvaser to communicate to our PC and we get 0 CAN errors, so how come our customer is having issues on their nodes?

    CAN waveforms are very network-dependent. The transmitted signal from any node could take on a particularly different shape when characteristics of the bus vary. Looking at a waveform could usually help track it down.

    Best,

    Danny