Not able to boot Nucleo-h755ziq

[BOSSX918spy]

Hi everyone,

I'm experiencing an issue uploading a simple onboard LED blinking program to my STM32H755ZIQ board. Every time I try to start a debug session, I get the following error:

STMicroelectronics ST-LINK GDB server. Version 7.9.0
Copyright (c) 2024, STMicroelectronics. All rights reserved.

Starting server with the following options:
Persistent Mode : Disabled
Logging Level : 1
Listen Port Number : 61234
Status Refresh Delay : 15s
Verbose Mode : Disabled
SWD Debug : Enabled
InitWhile : Enabled

Info : default port : 7184
Info : Remote address: 127.0.0.1
Info : stlinkserver already running, exit
Target no device found

Error in initializing ST-LINK device.
Reason: No device found on target.

What I've Tried:

Hardware Checks:

• Verified that the board is powered and that I’m using a known-good USB cable and port.

Software and Firmware:

• Updated the ST-LINK firmware using STM32CubeProgrammer.
• Ensured that there are no extra instances of the ST-LINK server running (rebooted the Mac and checked Activity Monitor).

IDE Configuration:

• For the H755ZIQ (dual-core device), I commented out the code that releases the Cortex‑M4 core so that only the Cortex‑M7 is active.

Despite these steps, the ST-LINK GDB server still fails to detect the device, and the board doesn't even enter debug mode.

Has anyone encountered a similar issue with the STM32H755ZIQ, or does anyone have additional suggestions to get past the "No device found" error? Any help would be greatly appreciated!

Thanks in advance for your time and support.

[Hal56-GCI]

The thing that really baffles me is that the first time I programmed the board it worked. Then after a power down and repower it didn't. Then I had to go through what I described in my previous message before it eventually started working again. No change was made to the code or project files.

[Tesla DeLorean]

>>The thing that really baffles me is that the first time I programmed the board it worked. Then after a power down and repower it didn't.

That's an H7 thing, a power cycle is a proper reset, the normal NRST/NRESET methods don't do a complete reset, especially when it comes to latching Option Byte settings, etc. I think it's supposed to protect against glitching methods to compromise protected parts.

The BOOT0=HIGH recovery method, where the System Loader recovers the SMPS vs LDO state needs you to power cycle the chip/board.