Having issues with FlexCAN on PXS20 (now MPC5643L)

[acascarino]

Our project is using two PXS20s (now MPC5643Ls) on two separate PCBs, which communicate via a CAN bus. We are experiencing an issue where messages from one processor on one board appear intermittently to send twice, even with the presence of an ACK bit from the other processor. We are very certain that we are copying the message into the relevant register only once, and yet we are seeing two identical messages appear on a scope trace of the CAN bus, both with ACK bits set. Has anyone else seen this issue, and if so is there a fix or a workaround? The double-messaging is causing erroneous dropped message errors within our project and the suppression of these errors is obviously masking other real errors which we would much rather be able to detect!

Thanks in advance.

[PetrS]

Hi,

There could be incorrect bit timing or clocking. So please double check that
- a valid CAN bit timing is programmed

- the peripheral clock frequency is not smaller than the CPI frequency

- there must be a minimum ratio between the peripheral clock frequency and the CAN bit rate, as specified in Table 24-11 of the Reference Manual.  

BR, Petr