Not able to connect to NUCLEO-H755ZI-Q

[Marco.D]

Hi,

I am developing some code for a display interface on a NUCLEO-H755ZI-Q, I debug some basic code and the STM32 seem to have crashed.

Now I can not connect anymore to it, not even with the CubeProgrammer V2.5.

Is there a way to recover the Nucleo board from this?

[Uwe Bonnes]

Double check jumpers, check and exchange cable and hubs.

[Tesla DeLorean · Accepted solution]

Most likely a SMPS/LDO or VOS setting.

Solder a two pin header between VDD and BOOT0 (BT0) pin, and use one of the spare jumpers parked on the back of the board.

Jumper VDD to BOOT0 connect/disconnect the board a couple of times (cycles power) until STM32 Cube Programmer can see the H7, and then erase the user code off it.

[Marco.D]

Amazing thanks,

it worked at the first attempt!

What does this trick do?

I am looking at pag 143-145 of the reference manual

The option bytes used will be from the TCM ram, is it just that?

Thanks,

Marco

[Tesla DeLorean]

The H7 is an odd bird.

NRST doesn't work as a complete chip level reset, and the device remembers things like LDO and SMPS settings across uses.

Watch very carefully the code you have in SystemClock_Config(), and especially unbounded while() loops. The code might actually be running by dies in a way you can't recover. The BOOT ROM (System Loader) provides a safe-harbour from which to connect from, and to resolve settings issues.

The method described earlier was used in the H747I-DISCO to recover it, there have been several topics about that, and H7's in general. I broken mine early by using H743ZI startup code rather than H747I-DISCO compatible code.