Is it possible to use HSI48 clock in stm32f048t6 for DFU bootloader in virgin device?

[DBalz.1]

Hi all,

I'm using STM32f048t6.

I would like to load code using DFU bootloader for virgin device using HSI48.

The boot configuration is correct using BOOT0 pin.

Is it possible or I need an HSE?

Note: after a jtag programming the USB works correctly. At hardware level, the USB signal are connected directly to MCU pins.

Thanks

Damiano

[Uwe Bonnes]

According to reference manual, it is possible with Clock Recovery System (CRS)

[DBalz.1]

Thank you for the response!

The AN2606 reports:

"The clock recovery system (CRS) is enabled for the DFU bootloader to allow USB to be clocked by HSI48 48 MHz."

But it's not working.

Are there any flags to be set or some other settings?

At hardware level, the required pull-up are correctly setted by the bootloader or we need to add them externally?