STM32WL55JC intermittently fails to wake from shutdown

[Andy_]

I have a STM32WL55JC part that spends a lot of time in shutdown mode. It's woken by an alarm on the internal RTC. However intermittently it fails to fully wake up.

This is almost certainly a hardware fault - certain PCBs are more susceptible than others. The alarm is definitely triggering because there's a status LED on the PCB, and when it fails the LED illuminates dimly. 

If anyone has any ideas of where to start looking it would be greatly appreciated. This is my first project using an ST part, so there's quite a learning curve. 

[STTwo-32]

Hello @Andy_ and welcome to the ST Community.

It may be an issue on the HW design. So, first refer to a RF Hardware design expert to help you discover the potential issues of your design. Also, you can use a NUCLEO-WL55JC1 to test your code if it is working or not. If so, then the issue is a HW one. If not, you need to double check your Code. You may also refer to this example. 

Best Regards.

STTwo-32