2025-10-26 9:58 AM - last edited on 2025-10-29 3:59 AM by Andrew Neil
I was configuring USB as virtual com port for stm32f401ccu6 (Black Pill) using HAL. I am getting clock issues. I tried multiple times but can't resolve them. please help me.
2025-10-26 10:48 AM
Hello @Clockarz
Could you please give more details about the issue you have?
If you put the cursor on the red rectangle (on the PLL source Mux), what is the message you have?
Are you reproducing this issue using the STM32CubeMX V6.15.0 (or the plug-in integrated on the STM32CubeIDE V1.19.0?
If not try to update your SW to the last versions.
Also, have you tried the resolve clock issue button?
Best Regards.
II
2025-10-26 10:53 AM - edited 2025-10-26 11:12 AM
For USB you have to use/select the HSE.
Set in RCC HSE to crystal, to do this..
...+ write the correct frequ. of the real mounted crystal (check!) on your board here:
Then adjust PLL/divider , to get 48M for "48M clocks" and the core clock you want.
2025-10-29 3:31 AM
Hi @Clockarz
It is mentioned in the reference manual:
USB OTG FS require an external clock (HSE) multiple of 1 MHz (ranging from 4 to 26 MHz).
Also, the USB OTG FS clock (48 MHz) and the SDIO clock (≤ 48 MHz) which are coming from a specific output of PLL (PLL48CLK)
To give better visibility on the answered topics, please click on Accept as Solution on the reply which solved your issue or answered your question.