STM32WB55 - Bluetooth not working when setting RFWKP Clock to LSE

[Reno]

Hi all,

I am using a custom board which is very similar to this one here: 

https://github.com/WeActStudio/WeActStudio.STM32WB55CoreBoard/blob/master/Hardware/WeAct-STM32WB55CoreBoard_V10%20SchDoc.pdf

I am using this tutorial as the main setup reference:
https://www.youtube.com/watch?v=Zgw3wRpGSRQ 

Initially, it doesn't work for me, as the service just doesn't show up in BLE TOOLBOX. After a lot of fiddling, I eventually nailed down to the RFWKP clock settings, only when I set it to HSE, will Toolbox manage to discover the service, if I follow the video's suggestion and set it to LSE, it won't work.

I am wondering the reason why, and if there is any remedy for this.

Any suggestion will be very much appreciated.

Thank you.

[STTwo-32]

Hello @Reno and welcome to the ST Community :smiling_face_with_smiling_eyes:.

I think this is due too a HW issue. I suggest you to use the recommandet Capacitance and cristal on the table  on the table 1 of the AN5290. Also, you have to ensure that X2, C14 and C15 are placed as close as possible to their respective pins. On the MCU to reduce the noise effect. Finaly as stated on the ES0394, there may be a problem on the LSE if you are having signal transition on the PC13, PH3 and Pa2.

Best Regards.

STTwo-32 

[Reno]

@STTwo-32, thank you very much for the prompt reply, this is very helpful, I will redo my board base on your suggestion to see if it solve the problem. It will take a bit of time but I will reply back my result once its done.

Thank you again for your support.

Reno

[Reno]

Sorry one more question, you mentioned C14, C15, do you mean the VDD decoupling capacitor, or you actually mean C5 and C6 (base on the schematic on AN5290) for the X2.

Thank you.

Reno

[STTwo-32]

Hello @Reno 

I mean the C5 and C6 (base on the schematic on AN5290) for the X2.

Best Regards.

STTwo-32