STM32H7B3 Issue: Low voltage from USB Power Supply and Inaccessible BOOT0 Pin

[Ayoub_Bnina]

I am currently experiencing an issue with my STM32H7B3I-DK board. The BOOT0 pin on the board is not externally accessible, which has been causing some difficulties to me.

Additionally, I’ve noticed a low and unstable voltage to the board. When monitoring the target voltage in CubeProgrammer, it fluctuates between 0V, 0.22V, and 0.35V what caused I think the faulty red led LD7 to lit up and the green led LD5 to lit poorly. This instability could potentially be contributing to the issues I’m facing, as I am no longer able to connect to the board through ST-LINK, I get No STM32 Target Found.

   

The issue suddenly occurred while I was wiring some cables to the board. I am unsure whether a short circuit might have occurred during this process or due to a misconfiguration from the uploaded code.

In an attempt to resolve the issue, I tried to strap the NRST pin to ground and perform full chip erase in CubeProgrammer but I couldn't manage to achieve the perfect timing. However, these efforts have not yielded any positive results.

Furthermore, I observed that when I remove the JP2, which is for current measurement according to the schematic, the LD7 turns off and the voltage returns to 3.27V. However, the LED associated with the USB OTG HS circuit (LD8) lights up, indicating an overcurrent occurred while I am connecting through the USB ST-Link port.

 

I would greatly appreciate any guidance or assistance.

[Tesla DeLorean]

Sounds like you've damaged the board or regulator.

Clamping NRST isn't a solution. The tools have a "Connect Under Reset" method

What I explained before, related to some H7 issues, is power cycling where BOOT0 is pulled high (system mode). To do this you'd need to find the circuit node, likely at one end of a resistor pad, to get access to BOOT0

[Tesla DeLorean]

Doesn't the STM32H7B3I-DK / MB1332 route BOOT0 to a SWITCH ?

[Ayoub_Bnina]

@Tesla DeLorean Yes, you're right there is a switch for flash or Sys Memory connected to boot0 pin I didn't notice it. The switch already pulled to ground which is flash mode.

[Ayoub_Bnina · Accepted solution]

Apparently the problem was in ST-link last firmware update, I was using a usb charger cable and the jumper was switched on STLK whithin the 5V power supply options. Before the update the board was working fine, After switching the jumper to CHGR 5V_USB_CHAGER the board powered up and worked fine but the MCU was getting too hot I don't know if there is still a short circuit, whether it is damaged or an issue that ST should fix in the coming firmware update.