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RM48L952: Questions about DCAN module of RM48L952

Jason-Zhang
Prodigy 30 points
Part Number: RM48L952


Hello :

      Now we are using the DCAN  module of  RM48L952 in our products, and we have a problem . We use a mailbox to send a message every 500ms ,  but sometimes we can't receive this message on CAN-BUS (it usually happens once  a day),and it lasts for 3 minutes, then everything come back to normal.

      IS this problem caused by DCAN  module itself?

      I found out that the TxOK bit in Error and Status Register can indicate if the message has been successfully transmitted, but there is only one TxOK bit for 64 mailboxes. How can I make sure that every mailbox has transmitted successfully? Or is there any other way to make sure every message is sent successfully ?

      We are looking forward to your answer!

      

  • 0
    TI__Guru 59540 points
    Hello Jason,

    First, the issue described in the first paragraph where you state you cannot receive a message on the CAN-BUS about once a day for approx.3mins.

    First, I assume, based on your later question, that the RM48Lxx device is the one doing the transmit and the "cannot receive" applies to other devices on the bus?

    So everything comes back to normal on it's own or is there some reset or other action taken to bring it back?

    Have you had a look at the CAN-Bus on a scope to see if the device is actually transmitting data and, for some reason, the rest of the devices on the CAN bus don't see them? Can you check if the CAN-Bus is in Bus OFF mode or some potential error state? This can occur if there is a catastrophic failure on the bus. Recovery should be faster than 3 minutes though.

    The other possibility is baud rate tolerance and the CAN bit timing settings. It could be that the bit timings are setup in a way that miss communication on the bus or that the baud rate error eventually goes out of synch enough to cause errors on the bus and after some time, eventually re-aligns. You should be able to see this on a scope as it enters into this mode.

    Finally, the TxOK bit indicates a successful transmission for each transmitted message. Since messages are sent serially, it can be checked after each message is sent.