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Dillon_TUNG
Associate
May 18, 2026
Question

STM32G0C1 USB 2.0 Type-C connection issue

  • May 18, 2026
  • 1 reply
  • 105 views

Hi everyone,
I have successfully implemented a USB VCP device on STM32G0C1 microcontroller, and it communicates perfectly with my PC.

To meet current product trends, I am migrating the connector to USB Type-C (schematic attached). I am keeping it as a USB 2.0 interface. For reference, here is my current pin configuration based on the schematic:

  • GND (Pins 1 & 12): Grounded.

  • VBUS (Pins 2 & 11): Left floating (my device is self-powered and does not require host power).

  • CC1 / CC2 (Pins 3 & 9): Each independently pulled down to GND via a 5.1kΩ resistor.

During testing, I encountered the following issue:

  • Using a Type-A to Type-C cable: The PC successfully recognizes the device and it works perfectly.

  • Using a Type-C to Type-C cable: The PC fails to recognize the device at all.

Could you please help me check if there is an error in my schematic? Are there any specific Type-C initialization rules or pin configurations that I must follow for C-to-C connections to work properly?

Thanks in advance for your help!s

 

Dillon_TUNG_1-1779074115220.png

1 reply

F
FBL
Technical Moderator
May 18, 2026

Hi @Dillon_TUNG 

For self powered device, VBUS sensing is mandatory. You can not left it floating. Management of VBUS sensing for USB device design - STMicroelectronics Community

A Type-C to Type-C cable will not enumerate unless the source detects your device and enables VBUS. Type-A to Type-C cable may bypass some of these issues because it does not require the same level of Type-C detection logic.

To give better visibility on the answered topics, please click on Accept as Solution on the reply which solved your issue or answered your question.Best regards,FBL
D
Dillon_TUNGAuthor
Associate
May 19, 2026

Hi @FBL ,

Thanks for your reply and the information provided. I've read through the AN4879 document regarding the USB specifications, but it doesn't seem to mention anything specifically about Type-C. I'm wondering if there are any differences I should be aware of?

Additionally, I tried disabling the USB peripheral initialization first ( by commenting out MX_USB_Device_Init() ) and used an oscilloscope to monitor the VBUS voltage when connecting to the PC via a C-to-C cable. I noticed that there was no voltage change at all. However, when I use a C-to-A cable to connect to the PC, I can clearly see VBUS outputting 5V.

Are there any specific rules or details I might have missed?

Best regards,
Dillon

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