NUCLEO-H755ZIQ "Bricked" behavior after unplugging during debug session

AraceliGuerrero · ‎2026-02-18

Hi everyone,

I think I’ve messed up my NUCLEO-H755ZIQ board. A few days ago, I accidentally unplugged the board while an active debug session was running. Since then, the board "dies" every time I power it off.

To get it back to a working state, I have to follow this tedious process every single time:

Set Boot0 to VCC.
Connect via STM32CubeProgrammer (Power Down mode).
Perform a Full Mass Erase.
Disconnect and set Boot0 back to GND.
Connect again and flash a simple .elf file (a basic SPI project that toggles an LED) just to verify it's alive.
After this, I can debug normally in CubeIDE—until I power cycle the board again.

This was manageable until I started working on a Bootloader project. Today, it took me all morning to recover the board because the bootloader logic seems to interfere with my "recovery" steps.

I’ve already tried messing with Option Bytes and performing several mass erases, but the issue persists. It feels like the flash or the option bytes are stuck in a state that prevents a normal cold boot.

Has anyone experienced something similar? Any idea which specific Option Bytes or sector settings I should check to fix this permanently?

Thanks in advance!

mƎALLEm · ‎2026-02-18

You need to do the same as you described in your original post and erase the MCU.

Then select 400Mhz for the system clock and select Direct SMPS compile and upload your application.

Normally it will work.

PS: in the product datasheet it was said that LDO is only available in boosted performance mode. Boosted mode is where the system clock is > 400Mhz at VOS0:

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View solution in original post

mƎALLEm · ‎2026-02-18

Hello,

What power configuration you set for that NUCLEO-H755ZIQ? you need to set the power as Direct SMPS otherwise you break the MCU. The default power mode for that board is Direct SMPS.

As the following:

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AraceliGuerrero · ‎2026-02-18

I don't have that option available. I can't remember which of the many features I enabled caused a conflict, but it has disappeared from my valid options. These are the only ones I have left, and LDO is currently selected.

mƎALLEm · ‎2026-02-18

Because most probably you have set the system clock > 400Mhz.

Direct SMPS is only available at System frequency <= 400MHz (VOS1)

So set the system clock at 400MHz and Direct SMPS option will appear.

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AraceliGuerrero · ‎2026-02-18

Yes, I configured the system clock to its maximum frequency of 480MHz.

mƎALLEm · ‎2026-02-18

You need to do the same as you described in your original post and erase the MCU.

Then select 400Mhz for the system clock and select Direct SMPS compile and upload your application.

Normally it will work.

PS: in the product datasheet it was said that LDO is only available in boosted performance mode. Boosted mode is where the system clock is > 400Mhz at VOS0:

To give better visibility on the answered topics, please click on "Accept as Solution" on the reply which solved your issue or answered your question.

AraceliGuerrero · ‎2026-02-18

Thank you! I was worried it was a more critical hardware failure; that's a huge relief.