Support Required – STM32WBA52 BLE Advertising Issue

[Hitesh2022]

Hello Team,

We have manufactured 500 boards using STM32WBA52CGU6. During testing, we tested 50 boards, out of which 5 boards are not advertising BLE, while the remaining 45 boards are working normally.

We have attached the schematic and PCB layout screenshots for your reference.

Our PCB is a 2-layer board, and we have not followed a controlled 50 Ω impedance for the RF trace. Could this be contributing to the BLE advertising issue on these 5 boards?

Could you please review the attached schematic and layout and help us debug this issue? We would also appreciate your guidance on the key parameters or measurements we should check

on the failed boards compared with the working boards.

[Laurent LOUAZON]

OK, wanted to check you were not having the very old cut1 that cannot be functional with new CubeWBA package.
But I see a “B” on picture, meaning you have cut2 so this is not the problem.

Seems 100nF decoupling cap (C41) is far form the STM32WBA reset pin.
As a test can you try to solder it close from the pad?

More generally, as using a 2 layers, I can see Vdd is routed on opposite side with all decoupling caps.
It is also crossing HSE and LSE lines.

 

Please try to set reset decoupling cap close from WBA.
Have you tried using LSI2 instead of LSE as I suggested in previous post?

 

Regards
Laurent
 

[Hitesh2022]

Hello,

We have checked by placing C41 close to the MCU pin, but we are still facing the same issue.

Could you please share the binary file for LSI2? We are getting an error while trying to change the LSI2 setting.

Regards,
Hitesh

[Hitesh2022]

Hello Laurent,

We have tested the BLE using LSI, and it is working fine.

However, we would like to understand why the BLE is not working when using the external clock.

Thanks for your support.

Regards,
Hitesh

[Laurent LOUAZON]

Hello,
Good news as it seems to clear point out the LSE xtal used.
As I said in my previous post, I was not able to find detailed datasheet for MU00525-32.768K. 
Can you get an exact ref and detailed datasheet for it?
Have you tried to use the one for our Nucleo kits?

Regards
Laurent
 

[RobK1]

I was not able to find detailed datasheet for MU00525-32.768K.

 

You need  to up your Google-fu, Laurent 😁.

3 seconds:

https://mm.digikey.com/Volume0/opasdata/d220001/medias/docus/6320/MU00525-32.768K.pdf

[Laurent LOUAZON]

Hi,

 

I was able to find this one but this is not what I call a detailed datasheet.

Missing the C0 for example to estimate the gmcrit as explained in wiki
HSE and LSE: How to select crystals and center oscillators with STM32WBAx - stm32mcu
 

It is very typical having such kind of “generic” reference but at the end you receive a 12.5pF Xtal while you think you have a 6pF xtal…

 

Laurent

[Hitesh2022]

Hello,

We are not able to find the LSI2 option in STM32WBA52. Please find the image below for your reference.

We accidentally tested this using STM32WBA55, where the LSI2 option is available. Please find the attached image for reference.

Could you please confirm whether the LSI2 option is supported in STM32WBA52?

Regards,
Hitesh

[Laurent LOUAZON]

Hello,
LSI2 is not officially available with STM32WBA52 but practically functional.
This is why you cannot do it through CubeMx but you can do it manually with modification described in wiki.

My idea was here to test LSI2 to see if this solves the concern so that we would confirm issue was related to LSE.
Based on your previous message “However, we also tested the LSE with the configuration shown in the image below, and it is working properly.”, should I understand you are now having a functional PCB and FW using LSE?

Regards
Laurent