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Associate III
February 22, 2026
Solved

USB issues with STM32F103C8T6

  • February 22, 2026
  • 1 reply
  • 222 views

Hello, I made a board with an STM32F103C8T6 which uses USB.
My issue is that when conecting USB (self powered or with external power) I get the following error on windows:

Windows has stopped this device because it has reported problems. (Code 43)

A request for the USB device descriptor failed.

Things I checked:
- When no USB is connected, the D+ line is pulled to 3v3, but when connecting the USB it goes down to 2.8 with 0.5v being on the resistor.
- Checked continuity from USB header to A11 and A12 pins (when unpowered)
- Resolder pins to ensure propper contact (Except FL1, I checked that everything else is proppery soldered, but I guess continuity is a good proxy test)

- Changed MCU, USB header and FL1 for new ones in case they got damaged

- Firmware was tested with a bluepill and everything worked.

It's been a week with this issue, if someone know what could be happening or could give me tips to help diagnose this I'd appreciate it.


Here are the schematics for that part of the board:

USB_sch.pngMCU_sch.png

 

 

 

 

 

 

And the layout:

USB_layout.png

Best answer by gbm

Check the wiring of USB-C connector. The common ones have alternating D+ D- D+ D- pins. On your PCB the wiring is D+ D+ D- D-  - looks strange to me.

1 reply

gbm
gbmBest answer
Principal
February 22, 2026

Check the wiring of USB-C connector. The common ones have alternating D+ D- D+ D- pins. On your PCB the wiring is D+ D+ D- D-  - looks strange to me.

My STM32 stuff on github - compact USB device stack and more: https://github.com/gbm-ii/gbmUSBdevice
Associate III
February 22, 2026

Yep, you were right.... thank you so much, Now I have to think how to solve it. 
My layout was D- D+ D+ D- and rechecking the datasheet it should be D- D+ D- D+.

Thank you so much for noticing this, it's been too long on this.