CAN on STM32F4xx

[chrismas9]

Do you have a Pyboard or any Nucleo or Discovery board with dual CAN MCU. It might be worth trying your hardware and test script on other hardware.

[kcoelho]

Do you have a Pyboard or any Nucleo or Discovery board with dual CAN MCU. It might be worth trying your hardware and test script on other hardware.

I think I managed to fix it.
The problem seems to go away after I initialize the Standby pins on each of the transceivers and then do a board reset.

Not entirely sure why this works but will try to make this repeatable to find the real reason why.

Thank you so much for your help

[chrismas9]

If the STBY is high or floating the device will sleep until it sees a dominant star on the bus. This means the transceiver at the listening end will wake up after a delay. The sending end will not wake up if you want to send. You need to either tie STBY low or drive it low before sending. It is also possible that the wakeup delay at the listening end (up to 40uS) may cause the beginning of the message to be lost.