ST-LINK Connection Error "DEV_CONNECT_ERR" with Nucleo-H755ZI Board

[DUBY24]

Dear Team

I hope this message finds you well.

I am currently working with a Nucleo-H755ZI development board (dual-core STM32H755) and encountering a persistent issue when attempting to program or debug the device using STM32CubeIDE and STM32CubeProgrammer.

The following error message appears:

Error: ST-LINK error (DEV_CONNECT_ERR)

Despite multiple attempts and following several troubleshooting steps—including verifying the BOOT0 configuration, updating the ST-LINK firmware, trying "Connect Under Reset", and attempting a full chip erase via STM32CubeProgrammer—the error persists, and I am unable to establish a connection with the device.

Here is a summary of what I have tried:

Verified all physical connections and USB cables.

Updated ST-LINK firmware.

Attempted connection using “Connect Under Reset” while holding down the Reset button.

Ensured I'm targeting the Cortex-M7 core, not the M4.

Attempted a mass erase in STM32CubeProgrammer.

Verified that no low-power or SWD-disabling firmware is loaded.

I would appreciate any guidance or recommendations you can provide to help resolve this issue. If further information or logs are needed, I would be happy to provide them.

Thank you for your support.

Best regards,

[TDK]

How can I recover my STM32H7/STM32H7RS board after... - STMicroelectronics Community

[KDJEM.1]

Hello @DUBY24 and welcome to the community;

May this How to solve connection errors when connecting and programming the STM32 target board can help you to solve the issue.

This article describes tips to prevent or fix errors encountered when connecting the STM32 target board to your computer.

Thank you.

Kaouthar

[DUBY24]

Thank you very much for your response. I would like to let you know that I carefully followed each step of the instructions you provided, including the changes in the reset mode configuration, connection frequency, and checking the BOOT0 pin state. However, despite all these actions, the error still persists and I haven't been able to establish a connection with the board. I really appreciate your support and would be grateful for any further suggestions you could offer to help me resolve this issue.