NUCLEO-U575ZI-Q board "Error: No STM32 target found"

[Rob Meades]

Using the STM32CubeProgramer (v2.16 from a Windows 11 laptop) with my NUCLEO-U575ZI-Q board has, from this morning, resulted in only the response:

UR connection mode is defined with the HWrst reset mode
ST-LINK SN : 003E004C3532510F31333430
ST-LINK FW : V3J13M4
Board : NUCLEO-U575ZI-Q
Voltage : 3.29V
Error: No STM32 target found! If your product embeds Debug Authentication, please perform a discovery using Debug Authentication

Looking at the various posts here about fixing programming issues, I have tried setting STM32CubeProgrammer to "Under reset" mode and holding the RESET pin down from power-on while I attempt to connect, but all that does is get me a different failure message:

UR connection mode is defined with the HWrst reset mode
ST-LINK SN : 003E004C3532510F31333430
ST-LINK FW : V3J13M4
Board : NUCLEO-U575ZI-Q
Voltage : 3.29V
Error: ST-LINK error (DEV_TARGET_HELD_UNDER_RESET)

I have also tried the same procedure but allowing the board to power on first and only then holding reset and trying to connect but that makes no difference whatsoever, back to the original error message.

I have connected to the board in update mode and made sure that the debug processor FW version is V3J13M4, which I believe is the latest, but that hasn't helped.  There is nothing connected to the board aside from the USB connection to the debug chip.

I have not been using either secure or low-power mode code on the device.

Any other recovery suggestions?

[Tesla DeLorean · Accepted solution]

Potentially issues with LDO/SMPS settings.

Add a jumper so you can short BT0 to VDD, check if you can connect to the device if it runs code from ROM. If you can connect Mass Erase.

On the H7 there was another trick to completely power cycling the boards a couple of times with the BOOT0 jumper in place. Not sure it's applicable to the U5, but might be worth a try if the issue persists. 

[Rob Meades]

BOOT0 is the thing!  Saved me a lot of hair pulling there, you have coffee/beer :-).