>>'With BOOT0 high cycle the power on the whole board ...' How do I do that?
Install the JP7 jumper
Remove ALL power sources from the board
Re-power the board
Perhaps repeat a few times.
The H7 has some modes of behaviour that will lock out the SWD connectivity, as POWER-UP and RESET have different modes of operation. These tend to occur when you have the LDO/SMPS settings wrong, and the H7 latches a mode that is inconsistent with the one the board is designed to be using.
https://www.st.com/resource/en/user_manual/um2411-discovery-kit-with-stm32h747xi-mcu-stmicroelectronics.pdf
Caution: A deadlock occurs if the board SMPS/LDO firmware PWR configuration does not match the hardware configuration: after the reset, the ST-LINK cannot connect the target anymore.
The firmware PWR configuration must be set as follows in function SystemClock_Config in file main.c:
• If the hardware configuration is “Direct SMPS�? (default configuration): HAL_PWREx_ConfigSupply(PWR_DIRECT_SMPS_SUPPLY);
• If the hardware configuration is “LDO�?: HAL_PWREx_ConfigSupply(PWR_LDO_SUPPLY);
If a deadlock occurs because of a mismatch between hardware and firmware PWR settings (SMPS/LDO), the user can recover the board by applying the following procedure:
1. Power off the board.
2. Connect pin BOOT0 to VDD using a wire (or short R192). This changes the BOOT0 pin to 1 instead of 0, thus changing the device boot address to boot address 1 and making the bootloader start in System memory. This avoids starting firmware in the user Flash with a wrong SMPS/LDO configuration versus the hardware board configuration.
3. Power on the board and connect using STM32CubeProgrammer (STM32CubeProg).
4. Erase the user Flash.
5. Power off the board and remove the short between BOOT0 and VDD.
6. The board is recovered and can be used normally with matching firmware PWR.
