STM32F070RBT using PLL with HSI RC

[CWedg.1]

Evaluating the STM32F070RBT6 for a project, and using STM32CubeMX V6.10 I am unable to connect the PLL to the HSI RC. It all works ok if I use HSE.

I'm wondering what I'm doing wrong.

[CWedg.1]

I get the message "PLL mux should have HSE as input".

[KDJEM.1 · Accepted solution]

Hello @CWedg.1 ,

Did you activate the USB?

If yes, note that the HSI cannot be used for the USB clock source. This behavior is mentioned in AN4879 and precisely in section 4.FAQs (frequently asked questions) and also in datasheet section 3.16 Universal serial bus (USB).

Thank you.

Kaouthar