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USB device not recognized - running crystalless USB on an STM32L422KBT6

MadCowKP
Visitor

I am desperately trying to get the USB interface to work on an STM32L422KBT6. On my custom-designed board, the microcontroller is connected to a USB port via two differential lines (D+ and D-). The board is powered by LDOs through the VBUS. Here is the board layout, with the BOOT0 pin subsequently pulled to GND (had forgotten to do that).

Platinenlayout.pngSchaltplan.png

In the Device Configuration Tool, under RCC, 'CRS SYNC' is set to 'CRS SYNC Source USB'. Under Connectivity -> USB, the checkbox for Device (FS) is checked, and under Middleware and Software Packs -> USB_DEVICE, 'Communication Device Class (Virtual Port Com)' is selected as the Class For FS IP. Programming is done with the ST-Link V2 debugger via SWDP. The Clock Configuration is as follows:

Clock Configuration.png

Regardless of whether I use MSI or HSI48 as the clock for the USB bus, I receive the error message: 'The last USB device you connected to this computer malfunctioned, and Windows does not recognize it.'

Despite reading numerous application notes and much more, I am at a loss. Can anyone tell me what I am doing wrong? Thank you in advance!

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