$0.11 PY32F002A: Cortex-M0+ MCU, actually a PY32F030! 32/4KB, 48MHz, PLL, DMA...

[ataradov]

When the device is in a hanged state, attach the debugger without reprogramming or resetting  and see where it is stuck. The way to do this depends on the software you are using.

[Pixie dust]

I was thinking about that as well. But I use uvision and it does not look that it allows you to do that without either resetting it or going through a program cycle.

[ataradov]

Of course it can do this. Any IDE that is worth using should be able to do this, and ARM's own can do that for sure. https://developer.arm.com/documentation/ka003020/latest/

[Pixie dust]

Thank you for this advice. Was not aware of this. Super

[Pixie dust]

Whatever I tried the moment I disconnect the debugger the same code on the same hardware seems to work differently. It has to do with the stop mode and the LSI clock which seems to cause some synchronization problem. Then I found out that you can enable the debugger in software without it being connected. This solved my problem as I got the same behavior with or without debugger connected. Here the 2 lines of code which made it work:
   // simulate as if debugger is ON by applying clock and enable stop mode   
   RCC->APBENR1 |=0x08000000;          // apply clock to debugger
        LL_DBGMCU_EnableDBGStopMode();