Strange behavour when coming out of standby mode

[SSmit.13]

Hi

  I have my own board with a STM32L433 , running on a battery. I place the processor in Standby mode, then exit it with the RTC AlarmA and periodic timer. As soon as it wakes up I initialize the uart and display a message on the terminal .When put in standby, it wakes up with the AlarmA, do some readings, then back into standby mode, then the periodic interupt wakes it up. Then back to standby for a while , then AlarmA wakens up and so on....

When I have the st Link plugged in all works well without any problems. If I remove the st link, and restart the board, some of the characters are all muddled up. I thought it might be a 0v issue, but checking the board all looks good. I have BOOT0 tied low, NRST tied high, and running on external 8MHz crystal. I have a pullup on the TX uart line.

I haven't a clue whats going on, anyone any idea what this might be?

 

Best Regards

Scott

[STOne-32]

Dear @SSmit.13 ,

Hope you are doing fine , wanted to check if the issue was fixed ? Most probably to check Clock setting and UART baud rate configuration, it may happen that system is using MSI clock and to do a sanity check on this piece of code .

have a great day,

STOne-32