STM32G4 USB to CAN bus bridge

Developers
1

The STM32G4 will hang in a reset loop after flashing with the option to use the MCU as a USB CAN bus bridge.
The USB SRAM isn´t writeable because the USB clock isn´t set.
Changing stm32g4.c line 107 from:

    // Enable 48Mhz USB clock using clock recovery
    if (CONFIG_USBSERIAL) {
        RCC->CRRCR |= RCC_CRRCR_HSI48ON;
        while (!(RCC->CRRCR & RCC_CRRCR_HSI48RDY))
            ;
        enable_pclock(CRS_BASE);
        CRS->CR |= CRS_CR_AUTOTRIMEN | CRS_CR_CEN;
    }

to:

    // Enable 48Mhz USB clock using clock recovery
    if (CONFIG_USBSERIAL || CONFIG_HAVE_STM32_USBCANBUS) {
        RCC->CRRCR |= RCC_CRRCR_HSI48ON;
        while (!(RCC->CRRCR & RCC_CRRCR_HSI48RDY))
            ;
        enable_pclock(CRS_BASE);
        CRS->CR |= CRS_CR_AUTOTRIMEN | CRS_CR_CEN;
    }

will also set the internal HSI48 MHz USB clock when no USB serial is used .

Cheers,
Stephan

1 Like
2

Thanks. Hopefully it is fixed now (commit f71d2c7c).

-Kevin