Nucleo-H755 ST-LINK MCU overheating and ST-LINK not detected

[durna]

Hello,

I am using an STM32H755 Nucleo board in a system where the board is plugged into a custom PCB via headers. The system has been working for about two weeks without any issues. Occasionally I remove the Nucleo board to update the firmware and then plug it back into the PCB.

Today the system stopped responding to UART commands. When I connected the board to my PC, STM32CubeIDE reported:

"No ST-LINK detected! Please connect ST-LINK and restart the debug session."

I also tried STM32 ST-LINK Utility and got:

"Can not connect to target! Please select 'Connect Under Reset' mode..."

However, STLinkUpgrade is able to detect the ST-LINK and perform a firmware upgrade.

Another important observation:

The ST-LINK MCU on the board (STM32F7) is getting very hot.

Additional diagnostics:

- The board was completely removed from the external PCB.

- Even when powered independently, the ST-LINK MCU still overheats.

- The board draws significantly higher current than normal.

- I cannot measure proper 3V or 5V rails on the board.

Because of these symptoms, I suspect the on-board ST-LINK MCU may be damaged.

Has anyone experienced a similar issue or can confirm if this behavior indicates a failed ST-LINK hardware?

Thank you.

[mfgkw]

> Because of these symptoms, I suspect the on-board ST-LINK MCU may be damaged.

maybe, or something else died of overcurrent or overvoltage (U regulators...)

Unfortunately you can not separate the ST-Link v3 here (as can be done with Nucleo boards including ST-Link v2).

But you can keep the ST-Link in reset, see https://www.st.com/resource/en/user_manual/um2408-stm32h7-nucleo144-boards-mb1363-stmicroelectronics.pdf 7.3.2

If this makes your ST-Link keep cool the board my be used with an external ST-Link via the MIPI-10 connector.

If not you will need a new board and take care of its strain in your custom PCB...

[KDJEM.1]

Hello @durna;

If the issue not yet solved, I recommend you to look at How to solve connection errors when connecting and programming the STM32 target board STMicroelectronics Community may 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 such as:  “No target connected”, “Target not found”, “No ST-LINK detected”, and “ST-LINK connection error”.

Thank you.

Kaouthar