The Problem: The STM32 Blue Pill sometimes dies for no apparent reason. On the PSU, it’s pulling 30mA and then for now apparent reason, the current draw reduces to 10mA (for the power indicator LED, presumably) and the microcontroller appears dead. It only seems to occur when powered from a power supply to the 5V pin. Once it occurs, giving the 3.3V pin power instead appears to do no good.
For some reason, I’ve been able to fix the problem reliability by removing external power and powering the STM32 via the Stlink clone along with the CLK, GND, and IO pins. Voltage SHOULD be voltage in such a situation, but maybe the IO pin has some kind of effect. I’m really not sure. If anyone knows, please pass on why.
I’ve wondered if the problem is some kind of BOR brownout problem, but I haven’t done the work to find out yet. It only seems to happen with the CS32F103C8T6 STM32 Blue Pill clones (which I currently have 9 of I need to burn through and never buy again.)