stm32H743,micropythonV1.23, Coroutines suddenly pause, resume automatically after plugging in USB

[chiyu-Charon]

I have a device running about twenty coroutines, primarily responsible for gathering various sensor statuses via CAN, UART, and I2C. The device operates normally for a period of time, but after an unpredictable period of time, the entire program appears to pause unexpectedly. Upon capturing packets, I notice that all communications have been Paused.
At this point, I plug in the USB cable and use a serial terminal tool to check for any potential issues or unexpected exceptions. However, as soon as I plug in the USB cable, the program resumes running without any abnormalities or error messages being logged.
I have verified that there is always plenty of memory available, and the power supply remains stable throughout this occurrence.
Has anyone encountered a similar problem? Could you provide some ideas or steps for troubleshooting the issue?

[bikeNomad]

Have you tried connecting the RX pin of a USB-serial adapter to the UART TX pin that's used for the REPL? This way you could monitor any printing or logging that leads up to the hang without plugging in the USB connector.

You don't say which board you have, but on the NUCLEO-H743ZI the REPL goes through UART3 and the ST-Link debugger chip, which might have something to do with the problem. On that board you could also then disable the ST-Link by putting a jumper on J1, so if the ST-Link is doing something funny you could find out.

[chiyu-Charon]

Thank you for your suggestion! I am currently only using the USB REPL and haven’t tried the UART REPL yet. I’ll make sure to look into how to configure and use UART REPL output so I can debug without plugging in the USB.
Do you have any related suggestions for me? Thanks again!