Pico stops sending can message halfway through, then retries

[Nate711]

Hi, I was having no problems when talking between two can transceivers connected to the same pico, but now when I talk to an external device (mg4005 can bus bldc motor), the Pico seems to try to send a message, fails halfway, then retries successfully. Any idea what's going on? Thanks!

[KevinOConnor]

That certainly looks odd. Make sure you are on the very latest can2040 code as there were some recent changes to the handling of transmit messages.

-Kevin

[Nate711]

Thanks for the response Kevin! I just checked and I'm using the latest main. It seems like I'm able to change how often these errors occur by changing the delay between sending messages. For instance, if I delay 200us between sending two CAN messages, the error rate seems to be low, like 1 in 10. However if I change that to 300us, it becomes maybe 1 in 2. Btw, the code I'm running is this: https://github.com/Nate711/can2040-test/blob/main/apps/mg4005_test.cc

[Nate711]

I sort of resolved one issue: In addition to the half-formed can messages, the pico would often (~1 in 3 times) repeat even a successfully sent and ACKd message (see below). I reduced this occurrence to maybe 1 in 5 by just removing my print statement that happened every time CAN messages were sent. Oops! I didn't realize the USB comms would add irq latency. Still have fix the half-formed message problem...

[Nate711]

Update: I removed the actuator and instead made CAN 1 talk to CAN 2 (both have transceivers) to see if the actuator was the issue. It was not. The program I used to test this sent 3 messages over can in a 1khz loop. Sometimes when I run my code, the 2nd message is always repeated, but sometimes if I restart the pico, the messages are totally fine. Maybe you can recreate this issue on your side. My code is: https://github.com/Nate711/can2040-test/blob/main/apps/dual_can_test.cc

[KevinOConnor]

Alas, I wont be able to help with code using can2040. A good test would be to see if you can reproduce the problem using known working code (Klipper) as described at https://github.com/KevinOConnor/can2040/blob/master/docs/Tools.md .

Cheers, -Kevin

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