stm32u5 CAN, How to cancel resend failed messages

[lll]

hello:

@mƎALLEm 

I'm currently working with the STM32U585 and ran into a problem abort CAN auto Retransmission.

Context:

1. There are three devices on the CAN bus: stm32u5, A and B
2. stm32u5 enable auto Retransmission
3. stm32u5 need to keep sending them messages, regardless of whether they are connected or not
4. device A and device B have hardware message filtering, So if A or B receives a message that is not intended for it, no ack will be sent(Is this correct?)

I want to know:

1. If A is online and B is offline, how many times will the message sent to B be resent
2. If it will be resent many times or never stops, how do I delete the failed resend messages after tx fifo is full

[mƎALLEm · Accepted solution]

Hello,

The ACK is sent whatever it's recipient or not. The ACK has no relation with the ID but to the validity of a CAN frame.

So if A and B are recipients at least one of them will acknowledge the frame. So if A is offline, B will always acknowledge. Same thing, if B is offline A will acknowledge no matter the ID used.