STM32H755ZI custom board not detected by ST-Link

[Aadi]

Hi community !

I was working on a custom STM32 board as part of a robotics project. We started evaluating STM32H7 through the Nucleo boards, and now that we've confident with our chip selection, I designed a custom nucleo-type board, which can later be integrated on our main robot PCB. Since we didn't need any additional features, main focus was to have a board with just the STM32 chip (STM32H755ZIT6) along with the basic components needed.

 

During the evaluation, I am not able to establish connection between ST-Link V3 MiniE, it shows "No target found". The board is powered by an 5V external supply, which powers the STM LDO, providing 3.3V for the chip. I tried playing around with the ST-Link config settings like Frequency, Mode, Reset Mode and Speed, but it doesn't help in fixing the error.

Upon testing the ST-Link with the Nucleo board, it is able to connect to the STM32 onboard (so the ST-Link board is working fine).

 

Upon reviewing my schematic, I realized that there were two mistakes:

1. I missed connecting VddSMPS to 3.3V, which I later fixed by soldering a wire.

2. In the BOM, I swapped all the 100nF caps (C12, C13, C14, C15, C17, C18, C19, C2, C20, C21, C22, C23, C3, C4, C5, C6, C7, C8, C9) with 1uF and swapped 1uF cap C11 with 100nF. I was not able to correct this mistake as the capacitors are too close to the IC, and they're of 0402 package. (My fault that I missed reviewing the BOM, seems to be a tool issue)

 

The voltage measured at Vcap is 1V, and all the Vdd pins are at 3.3V. Changing the voltage on BOOT pin doesn't help.

What might be going wrong in my board here ? I would appreciate a feedback on my schematic, if I am missing something or have made a mistake.  I'll be removing some of the incorrect caps to test later this weekend.

 

Thanks in advance !

 

[TDK]

Assuming the LDO power configuration:

VFBSMPS needs grounded.

VDDSMPS should be grounded.

Where are all of the other VSS pins? Only pin 6 is shown in the schematic. Guessing this is just visual.

There are some other minor things but no more showstoppers.

 

Also check chip orientation. VCAP voltage should be around 1.2V.

 

Ensure voltage is correctly reported in STM32CubeProgrammer. Pretty sure the MINIE has a level shifter so this is not optional.

 

If those aren't it, maybe provide a large in focus picture of the board close to the chip.

 

[Chaima_M]

Hello @Aadi , 

Please refer to the application note AN4938-"Getting started with STM32H74xI/G and STM32H75xI/GMCU hardware development", which provides guidelines and recommendations that are essential for reliable power‑up and SWD connectivity on STM32H7 devices. 

With best regards,

Chaima.