Get STM32H735G-DK out of deadlock!

[Stefan Meyre]

I can not connect my STM32H735G board via ST-Link anymore. "no stm32 target found". I tried "connect under reset" (ST Link Utility and ST programmer) as well as connecting boot0 to VDD.

Any idea how to erase the flash and start over? Cheers Stefan

[Tesla DeLorean]

The BOOT0 High trick requires that you power cycle the board several times, a reset is not sufficient. When the H7 is recognized you need to erase the broken user code.​

[Stefan Meyre]

Thx clive1; so I did change the power supply to the USB adapter (did power with the ST Link before). Therefore I could keep the ST-Link attached and did cycle the power while Boot0 was high (SW1 in SysMem position). Howerver I could not establish a connection to get to erase the flash. What could I possibly miss? I had no problems to recover my STM32F4s in the past...

[Tesla DeLorean · Accepted solution]

Powering with the STLK jumper is fine, the trick at least with the H747-DISCO was to completely disconnect the board from ALL power sources, and connect/disconnect the sole cable several times, with the BOOT0 pads solder bridged to VCC

The H7 has a weird reset methodology the NRST is not the same as the Power-On-Reset, which recovers settings/options from flash, as part of some security mechanism and starting thru ROM. If the Flash is not blank, it then transfers control.

Your code is perhaps executing, I think that putting some break-out/erase code to check a GPIO pin prior to the SMPS/LDO and VOS settings might permit simpler recovery. I'd probably use the BLUE USER button to nuke the device during future development.

[Stefan Meyre]

Clive, thank you; I got it to work the way you described. But not with the ST Utility but with the ST Programmer.

However a bit awkward the whole thing... Thx, Stefan

[Tesla DeLorean]

Yes, ST has been advised to improve how the recovery of this type of situation is handled. I had an early 747I and bricked the board very quickly. The unresponsiveness of the device was very disconcerting.

One of the related threads so I can find later

https://community.st.com/s/question/0D50X0000BqBA6TSQW/error-to-connect-to-target-stm32h747idisco

https://community.st.com/s/question/0D50X0000Bh5aWoSQI/stm32h747-discovery-kit-not-debugprogrammer

[Arno1]

Thought I'd add my 2c since I have the same issue.

My method to recover is as follows:

1. unplug the board (I power through the single USB cable, on ST Link connector)
2. Hold reset button
3. while holding the reset button, plug back in
4. computer indicates a new USB device (I'm on Kubuntu, YMMV)
5. connect with STM32CubeProgrammer
6. release reset button
7. Erase first few sectors (somehow a full flash erase does not work)
8. board should be fine for now

[JohnSigil]

Thanks for the hint about ST-Programmer, I too was unable to get it to work with ST-Link