STM32WL subGHz-radio clock source

[_martin]

Hi everyone,

I’ve designed a custom board based on the STM32WL55CCU6, but I accidentally left out the external HSE crystal. I'm wondering: is the HSE strictly required to use the radio features (specifically LoRa or LoRaWAN), or is it possible to rely on the internal HSI instead?

I’m aware that the HSI has higher frequency deviation compared to an external crystal, but since I also control the LoRaWAN gateway, I might be able to tolerate some drift or compensate for it.

Has anyone tried operating the radio using only the internal oscillator? Any guidance or experience would be greatly appreciated.

Thanks in advance!

[STTwo-32]

Hello @_martin 

For the ST32WL, The RF-PLL used as the frequency synthesizer for the generation of the local oscillator
frequency for both transmits and receive chains. This frequency synthesizer uses auto calibration and
uses the 32 MHz HSE32 reference. Also, the frequency of each sub-GHz radio internal oscillators is calibrated using the HSE32 clock. So, the HSE 32 Clock is needed.

Best Regards.

STTwo-32