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TCAN4550: Communication problem

Amy Luo
Expert 6895 points
Part Number: TCAN4550


Hi team,

In the process of using TCAN4550, it is found that the chip works normally when the communication rate is slow, but the later message lag when the communication rate is fast.

When the message rate is fast, the interval between two frames is about 300 uS. After sending for a period of time, reading TCAN4550 found that the message was sent before about 5 frames or 4 frames or maybe 3 frames.

The software was modified on the basis of TCAN455x Driver Library Demo_1.2_manifest. I would like to consult what may be the problem.

Best Regards,
Amy Luo

  • 0
    TI__Guru 74322 points

    Amy,

    When you say message rate are you referring to the CAN frame data rate, or the SPI clock frequency? Either way, this sounds like a SPI limitation, and because of overhead time for converting the messages from SPI to CAN, that delay will be more noticeable when your CAN messages are shorter.

    Please let me know which you are referring to, I can put together some suggestions to help depending on which case it is.

    Regards,

  • 0 in reply to Eric Hackett
    TI__Expert 6895 points

    Hi Eric,

    Thank you for your reply.

    CAN data rate is 500Kbps. SPI frequency is 10MHZ.

    Customers have carried out such tests: using debugging tools to send messages. After entering an interrupt, the global variable is added 1. When the interval is small, the number of messages sent by the debugging tool is larger than that of the global variable. Does this mean that nINT pin is not a frame of message produces an interruption?

    Best Regards,
    Amy

  • 0 in reply to Amy Luo
    TI__Guru 74322 points

    Amy,

    Thank you for that information. Can you clarify the question? I'm not sure I understand that "the number of messages is larger than that of the global variable".

    nINT can be used to indicate a message has been transmitted and received, but the interrupt has to be enabled in the register space, and their has to be another CAN node on the bus to transmit the ACK bit so the TCAN4550-Q1 knows the message was received correctly.

    Regards,