STM32H735 debug/flash problem

[Ksmol]

Hi, I have a board with STM32H735I.

I can only detect the IC when boot0 is tied to 3V3 effectively putting the MCU into DFU bootloader mode. In this mode, I can flash it OK with stlink or even USB-DFU. However, once I tie boot0 to gnd the device won't run correctly. and if I leave it at 3v3 it stays in bootloader mode.

I know someone else has posted about this, but no answers. https://community.st.com/t5/stm32-mcus-boards-and-hardware/stm32h735-problem-flashing-no-contact-to-%C2%B5c-while-boot0-gnd/m-p/570571#M14148

Schematics attached. I figured I must have some pin pulled up instead of down or similar.

 

thank you

 

[Peter BENSCH]

I miss some VSS pins in your schematics: Pin 12, 24, 45, 47, 64, 70, 81, 83, 93, 100, 106, 112, 119, 134, 137, 151, 159, 173. If you also connected them to GND, you should show the layout (signals from C37, C38, Y1 and GND layer) around Y1 and how the signals and GND are connected to the STM32. In the latter case, the crystal parameters, or alternatively the crystal type, are also important.

Not really relevant for your startup problems but not required: R51. Unlike MCUs of the last millennium, a pull-up is no longer necessary on NRST because it is internal.

Regards
/Peter

[TDK]

> the device won't run correctly

In what way? What does it do, and what are you expecting instead? Can you connect/program/debug over SWD?