ST‑LINK Mini V3E not detecting STM32H7 (Core ID error, high current when VTARGET connected)

[AEng7]

ST‑LINK Mini V3E not detecting STM32H7 (Core ID error, high current when VTARGET connected)

I’m debugging an issue with a custom STM32H7 board and an ST‑LINK Mini V3E. The setup includes a main PCB and a separate power PCB. So far:

Power & Basic Checks

• 3.3 V and 24 V rails are correct.

• Board current consumption is low when powered from either an 8 V or 24 V supply.

• Connections between the ST‑LINK Mini V3E and the main PCB have been verified.

Problem

• When I connect VTARGET from the ST‑LINK to the board’s 3.3 V rail, the current spikes and something starts to smell hot.

• STM32CubeProgrammer shows no target voltage, no device ID, and fails to read the core ID.

• The ST‑LINK is detected by the PC normally.

Additional Tests

• Tried a second main PCB and a different ST‑LINK Mini V3E, powering only through the ST‑LINK (no external supply). Same result: STM32CubeProgrammer cannot detect the STM32H7.

• I’m aware that VTARGET on the Mini V3E is an input, so I’ve tied it to the board’s 3.3 V rail as required.

Next Steps I Plan to Try

• Measure resistance between 3.3 V and GND to check for shorts.

• On PCB #1, pull BOOT0 high with a 10 kΩ resistor (removing the existing 10 kΩ) to see if the MCU becomes detectable.

• Re‑verify grounding between the PC, ST‑LINK, and the board.

• Try a different ST‑LINK model (non‑Mini).

[TDK]

Sounds like the grounds are not connected. Connecting 3.3V to the vtarget input would not cause issues. Something is miswired, hard to know what without seeing the setup.

With everything else connected, take a multimeter and measure between gnd on the programmer and 3.3v on the device.