STM32G0B1 USB fails to request device descriptor
Hi, I'm running into problems registering USB interfaces on STM32G0B1KBU6. The same code works fine on STM32F1*, STM32F7*, and STM32G4*.
Environment: latest STM32CubeIDE (v.1.13.2) @ Windows. Target: custom board with STM32G0B1KBU6, which uses the following peripherals: USB, CANbus, 9x PWM out lines and a digital GPIO in (the details are below). Flashing is done over SWD using either ST-Link v.2, or J-Link Base, directly from the CubeIDE.
For debugging, I've reduced the problem to a new and empty CubeIDE project for this chip, adding only the USB and one timer. No custom code: just what's generated by the IDE. No matter what USB device class is selected in *.ioc->Middleware and Software Packs -> USB_DEVICE -> Class For FS IP, the device fails to be recognized by the host (both Windows and Mac). The message provided by a Windows host is "Device Descriptor Request Failed". If I step over the init functions, the host reports this message exactly when the following stack flips the USBx->BCDR.USB_BCDR_DPPU bit:
HAL_PCD_Start() at stm32g0xx_hal_pcd.c:981 0x8001302
USBD_LL_Start() at usbd_conf.c:474 0x8005d86
USBD_Start() at usbd_core.c:378 0x80056cc
MX_USB_Device_Init() at usb_device.c:82 0x80058dc
main() at main.c:96 0x8000238
The USB stack never requests any of the device descriptor fields (doesn't hit the breakpoints there), although the valid descriptor is passed correctly by MX_USB_Device_Init() into USBD_Start().
On the hardware side:
- the device is powered by the USB's 5V rail via a 3v3 LDO
- power at the chip is verified stable 3v3, decoupled with a 1uF and a 0.1uF right by the power pin
- the USB is connected via USB-C plug, with CC1 and CC2 grounded via 5k1 resistors (one per pin)
- there's USBLC6-2P6 between the plug and the PA9/PA10 of the chip. Removing/replacing it doesn't change the outcome
- replaced the STM32 chip to ensure that it wasn't a hardware issue -- no change
- verified that the firmware is written correctly by dumping it in jlink.exe
- for debugging, all peripherals are removed and/or disconnected
- captured the full a USB traffic log in logic analyzer.
Please let me know if I should provide the USB capture or any other info.
Hope this has a known solution. Thank you so much for looking into this!