STM32G0B1RE Usb CDC descriptor not read, but USB DFU flash OK

FloSolio · ‎2025-10-09

Hi,

I'm try to communicate between my windows pc and my STM32GOB1RE Nucleo 64 board, with the CDC Class.

To validate my hardware ( PA11 PA12 and gnd connected to usb pc), i did few dfu flahsing operation with CubeProg without issue. Windows detect properly my device in DFU mode, i can do the programmation and new firmware runs well. -> Hardware looks fine.

I have generated the code with CubeMX and i'm using the HSI to 60mhz. Just this simple code with USB_DRD_FS

Usb clock derived from it at 48Mhz.

I'm also using the SOF detection and CRS SYNC Source USB.

I have added th Code line in usbd_cdc_if, but it is not really the problem.

Windows generate Error of not Descriptor reading.

Here is the log of the USB Device Viewer, a windows tool that bring information:

[Port7] FailedEnumeration : Périphérique USB inconnu (échec de demande de descripteur de périphérique)

[Port7] FailedEnumeration :  Périphérique USB inconnu (échec de demande de descripteur de périphérique)


Is Port User Connectable:         yes
Is Port Debug Capable:            no
Companion Port Number:            0
Companion Hub Symbolic Link Name: 
Protocols Supported:
 USB 1.1:                         yes
 USB 2.0:                         yes
 USB 3.0:                         no


       ---===>Device Information<===---

ConnectionStatus:                  FailedEnumeration
Current Config Value:              0x00  -> Device Bus Speed: Full (is not SuperSpeed or higher capable)
Device Address:                    0x00
Open Pipes:                           0
*!*ERROR:  No open pipes!

          ===>Device Descriptor<===
*!*ERROR:  bLength of 0 incorrect, should be 18
bLength:                           0x00
bDescriptorType:                   0x00
bcdUSB:                          0x0000
bDeviceClass:                      0x00
*!*ERROR:  Device enumeration failure

I don't understand why i'm able to transfert firware to memory through my DFU operation, and i'm not able to send the descriptor informations to windows.

May be a small thing is missing somewhere...

FloSolio · ‎2025-10-09

I join the simple project in a zip file.

Here is the descriptor in usbd_desc:

We can see that bLength is 0x12 = 18.

__ALIGN_BEGIN uint8_t USBD_CDC_DeviceDesc[USB_LEN_DEV_DESC] __ALIGN_END =
{
  0x12,                       /*bLength */
  USB_DESC_TYPE_DEVICE,       /*bDescriptorType*/
  0x00,                       /*bcdUSB */
  0x02,
  0x02,                       /*bDeviceClass*/
  0x02,                       /*bDeviceSubClass*/
  0x00,                       /*bDeviceProtocol*/
  USB_MAX_EP0_SIZE,           /*bMaxPacketSize*/
  LOBYTE(USBD_VID),           /*idVendor*/
  HIBYTE(USBD_VID),           /*idVendor*/
  LOBYTE(USBD_PID),           /*idProduct*/
  HIBYTE(USBD_PID),           /*idProduct*/
  0x00,                       /*bcdDevice rel. 2.00*/
  0x02,
  USBD_IDX_MFC_STR,           /*Index of manufacturer  string*/
  USBD_IDX_PRODUCT_STR,       /*Index of product string*/
  USBD_IDX_SERIAL_STR,        /*Index of serial number string*/
  USBD_MAX_NUM_CONFIGURATION  /*bNumConfigurations*/
};