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TMS570 CAN Bus failures

Richard Burke
Expert 1910 points

Hello,

We are looking at potential failure mechanisms for our product that uses a TMS570 LS1227 processor.

The question has been asked whether a CAN node can still receive data when it has a faulty CAN Tx line, for example if the line between the processor CAN Tx line and the CAN transceiver becomes open circuit. Clearly it would not be able to acknowledge a message but if there are at least 2 other nodes on the bus, all messages will still be acknowledged by one of the other nodes. In this scenario would the processor still receive CAN messages?

Are there any any other failure mechanisms whereby a processor may be able to receive but not transmit CAN messages?

Thanks in advance for any help.

Richard

  • 0
    Guru 15175 points
    I worked around with the CAN Bus, but it is necessary to have two Rx and Tx lines, for it to work properly, if one of the lines breaks then be impossible to transmit information.

    (This is an assumption) Now if we go to if the CAN bus is implemented in a car, if I remember correctly, the car has case earth and all devices are connected to this earth, perhaps in the event that the CAN bus also earth is connected car and thus there is no reference signal so that it can transmit data without the need for two lines.
  • 0 in reply to Martin Valencia
    Expert 1910 points
    Hi Martin,

    Thanks for your reply but unfortunately it doesn't answer the question. I know the CAN bus would not work properly but the question was whether there was a scenario where it could still receive data without being able to transmit.

    Regards,
    Richard
  • 0 in reply to Richard Burke
    Expert 1910 points
    I should also re-emphasise that I am not talking about a disconnection in the CAN High and CAN Low lines but a disconnection in the CAN Tx line between processor and CAN transceiver.
  • 0 in reply to Richard Burke
    TI__Mastermind 22375 points

    Richard,


    If you have 3 or more nodes on your CAN network, and one has the TX pin from device to transceiver disconnect, this node will still be able to receive CAN traffic.

    The acknowledge will be done by one of the other node.

  • 0 in reply to Jean-Marc Mifsud
    Expert 1910 points
    Thanks Jean-Marc, that was my assessment too. I am assuming that when an attempt is made to transmit a message a bus off event would occur so if we want to be in a known state we should perhaps disable reception in bus off.

    Regards,
    Richard