STM32L052T6Yx usb(virtual port com) to pc

[Fabrizio70]

I want use this mcu STM32L052T6Yx  to communicate via usb (virtual port com ) whit pc (whith linux system operativ).

THE power supply of mcu is 3.3v, can I problems if i directly connect PA11 PA12 PIN  to the pc usb (common ground)? , moreover  on pins PA11 PA12 I have not connected any pull-up pull-down resistor , it is right?

[TDK]

PA11/PA12 should be connected directly to the USB data lines. It has an embedded pullup resistor so an external one is not needed. The signal voltage on the data lines is only 3.3V despite power being 5.0V.

[Fabrizio70]

one last question , for the usb , do i have to connect any external oscillator to the mcu ?

[TDK]

On the STM32L0x2 you can use the Clock Recovery System to generate an accurate-enough clock for USB using the internal HSI48 oscillator. No external clock source needed.