STM32: STLink won't connect through SWD any longer

Question

The first flashing went fine, subsequent flashings fail with

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

On an STM32H745 NUCLEO board I have enabled the DEBUG interface and SWO pin by mistake. Is there a way to hard reset this board ?

Answer 1

The "flashing under reset" trick did not work. That is, holding the reset button pressed and immediately releasing it before STM32_Programmer does its thing through ST-Link. A bit of RTFM-ing sometimes helps:

If a deadlock is faced due to a mismatch between the HW
board setting and the FW setting (LDO/SMPS), the user can
recover the board by doing the following:
- Power off the board
- Connect CN11 ‘BT0’ pin (BOOT0) to VDD using a wire
- This changes the BOOT0 pin to 1 instead of 0 and thus the
device boot address is changed to boot address 1 making the
bootloader starting in System memory, instead of starting the
FW in the user Flash (FW that is setting a wrong LDO/SMPS
configuration)
- Power on the board and connect using
STM32CubeProgrammer
- Erase the user Flash
- Power off the board and remove the wire between BOOT0
and VDD
- The board is now recovered and can proceed normally.

Now I got to figure out why it goes deadlocked as soon as I flash my bin... commented some bits of code and rebuilt, sill does it.

LE: found the offending lines:

  HAL_PWREx_ConfigSupply(PWR_LDO_SUPPLY);
  ...

My SystemClock_Config function was all written for LDO power instead of SMPS