We are developing a USB prototype based around STM32F302C8. I cannot get this device to enumerate on USB, using either my own firmware, or the ST examples in STM32Cube_FW_F3_V1.11.0\Projects\STM32F302R8-Nucleo\Applications\USB_Device
There is some activity on the bus, but All setup transactions are ignored by the device - not ACKed, not NAKed, nothing.
In the firmware, I see the USB reset interrupt and try to configure the control endpoint - BUT, I can see in IAR register viewer that my attempt to write to USB_EP0R have NO EFFECT. Writes to other USB registers including USB_CNTR show in the register viewer as expected. So, it seems that something is configured in a way so as to prevent access??
I've verified that the PLL is running at 48MHz. The HSE is supplied at 12MHz.
When I switch the BOOT pins to boot into USB DFU, the device enumerates as expected, so I believe that USB is physically connected properly.
