STM32WB55CCU6 low energy Bluetooth microcontroller without USART interface

[LauraCx]

I am using the STM32WB55CCU6 low energy Bluetooth microcontroller. As I am not using the USART interface and don't need to support a Real Time Calendar clock, I didn't attach an external low frequency crystal resonator. However, I am wondering whether this was a mistake as the BLE Bluetooth interface requires a low frequency clock [ RTC ] and it doesn't seem possible to use the internal low frequency clock [ LSI ] - disabling RTC also disables the RF section in the .ioc file.

Is there some form of work-around that allows for the use of the internal low frequency oscillator ?

@JBlac.1​ 

[Remy ISSALYS]

Hello,

If you don't have an external low frequency crystal resonator, you should use HSE/1024 clock as input for RF system wakeup clock. The BLE doesn't require RTC to work, RTC is required in the application for the timer for example.

Best Regards