Why does MBED hang when it boots due to Fatal Error?

[JohnnyK (Jan Kamidra)]

Hello,

@John_Doe

Is this to be expected with MBED OS? Is MBED hung in some loop?

yes, this is standard Mbed OS behavior. The Os will save data in specific part of memory when an exception occured, then restart it self. After restart it will print out the error, and stay in a loop with specific led blinking patern.

@John_Doe

Perhaps we have a bug (good chance), but I am accustomed to a reboot, board comes back up running, after such a fatal error, on other RTOS I have worked on.

I won’t say what is correct or best, but for me the behavior is OK. I do not want release a program with auto crash restart I want to identify and solve the issue. But it depends on situation and I can imagine it can be like temporary workaround.

@John_Doe

Maybe there is some MBED parameters, settings we need to configure to allow for auto reboot, come back up running?

Yes of course it is possible. Please be so kind and take a look to post below.

How to effectively use watchdog in mbed?

Hello, just for info, you can handle MbedOS crash according to Error handling - API references and tutorials | Mbed OS 6 Documentation and additional info is here. According to platform/mbed_lib.json are necessary setting already set for auto reboot of your target. However the counter is set to 1 so the MbedOS will stop after first crash, but it can be solved in two ways. insert the function below before the main. That will reset the counter every time when a crash occurs void mbed_error…

Hope this helps and happy bug hunting.
BR, Jan