USB CDC doesn't work on STM32F3-- devices, but works fine on STM32F4-- devices.

[MWats.1]

I have been using USB CDC for a while now with the following STM32 parts;- F417, F401, F070, F301 and F373. I use STM32CubeIDE and all my projects are built using the Device Configuration Tool. I have found that USB CDC works first time with F417, F401, and F070 parts, but does not work with F301 and F373 parts. By 'not work' I mean the project build and run okay, but I get no enumeration form my PC. I get zero response. I have spent along time checking signal levels and clocks, etc, but found nothing. So, I've had to give up with the F301 and F373 parts. Could this be an issue with the F3-- library?. I would be very interested if anyone else has experienced this.

[waclawek.jan]

The 'F3 (as well as 'F1) don't have the internal DP pullup, you have to pull it up externally, see the respective DISCO boards.

I don't know about the Cube libraries, I don't use Cube.

JW

[MWats.1]

Interesting, thanks. I haven't considered that. I was originally using the the F4-- parts and then moved to the F3--, where I have seen the issue. I will check this out later today.

[MWats.1]

I have just added to 1.5k resistor to between +5V and +DP, on my F373 board and it works. So, thanks for the advice.