Can't connect to STM32H7 on SEGGER or JLink

[FSkro.1]

I can't connect to STM32H7B3I on SEGGER or using JLink. Resetting option bytes on JLinkSTM32 fails. If there is somehow irreparable damage, could that have been due to me programming high or low frequencies (1-400 MHz) in the RCC? If not, what could be the cause?

[Tesla DeLorean]

Posted to wrong subforum.

Try power cycling the H7 with the BOOT0 pin pulled/strapped high, and then try connecting. And mass erasing the flash.

I​f that recovers the part look at the VOS and LDO/SMPS settings in your code.

Connection under reset requires NRST to be wired​ on the debug header.

[FSkro.1]

Thanks. Where can I find the boot0 pin on my model?

[Tesla DeLorean]

Don't know what board and connections you have. The data sheet would enumerate the pins.

[FSkro.1]

STM32H7B3I-DK is the model name, but the datasheet gives many different pin names for boot0 and so I'm not sure what to look for on the physical board. How do I figure out which pin assignment applies to mine?

[Tesla DeLorean]

Some reason you can't use the on-board ST-LINK/V3? Do you need to hold that in reset (CN13) to be able to use an external debugger via the Tag-Connect header?

The BOOT0 pin is controlled by SW1 as I recall.

https://www.st.com/content/ccc/resource/technical/layouts_and_diagrams/schematic_pack/group1/b0/44/a0/bc/69/30/45/d9/MB1332-H7B3I-C01/files/MB1332-H7B3I-C01_Schematic.pdf/jcr:content/translations/en.MB1332-H7B3I-C01_Schematic.pdf

https://www.st.com/resource/en/user_manual/dm00610478-discovery-kit-with-stm32h7b3li-mcu-stmicroelectronics.pdf

[FSkro.1]

Thanks. I tried powering the board on with the switch at 1, but nothing changes when I try to connect on SEGGER or using JLinkSTM32 (with device family set to stm32h743). Would it make a difference to download STM32CubeProg?