What harms STM32

[Maprex]

Hey everybody. I had 3 STM32 F401RE for my robotic project but now I got "no stlink detected" error. Once I turned my computer off with shot down and then on again I couldn't get stm32 to work again, that's why one of them went away, the other one was when I turned the driver on and off while the stm32 was connected to the stepper motor driver and then it went away, i don't remember the other one. My first question is are these stm32s completely broken, can i save them? My second question is if they are completely gone, how can i save my next purchases?

[Peter BENSCH]

What tool is giving this error?
What ST-LINK are you using?
Can you share a photo from back and front of the ST-LINK?

Regards
/Peter

[TDK · Accepted solution]

If they were working before, and no longer are, probably the hardware is damaged. Most likely this is due to an overvoltage condition. Especially if it's happening repeatedly.

With motor applications, you should pay attention to inductive loads and ensure you have a flyback diode to prevent overvoltage and backpowering.

https://en.wikipedia.org/wiki/Flyback_diode

[Maprex]

Helle Peter, I am using normal STM32 F401RE and the ST-LINK comes embedded in Nucleo Board. When I jumped in the CubeIDE it gives the error

[Ozone]

> ... the stm32 was connected to the stepper motor driver and then it went away, ...

Attaching inductive loads without proper protective circuitry is the surest way to kill off any MCU.

[Maprex]

Thanks for your replying but I wired only PWM and Direction signals to STM32

[mƎALLEm]

Better to show schematics so others can identify the issue in your design.

[Ozone]

> ... but I wired only PWM and Direction signals to STM32

Large inductive loads (like stepper motors) can create local spikes of hundreds of volts.
If you don't take hardware precautions, those spikes will reach through your driver circuit or power supply, and kill the MCU.