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.

[Imen.D]

Hello ​@Hitesh2022,

This is not my area of expertise, but I recommend you follow the AN5948, try checking and correcting the impedance using discrete components. STM32WBA antenna matching 

[Laurent LOUAZON]

Hello,

 

I see one big concern.
C12 must be 470nF and not 4.7uF.
This is mandatory and could explain for sure issue you observed.

Also for for oscillators, please check below wiki page.
HSE and LSE: How to select crystals and center oscillators with STM32WBAx - stm32mcu
You should use a 8pF Xtal for HSE and not set any external caps  (C16/C17).

 

Finally, as using STM32WBA52 (meaning a LDO version so that current consumption is not optimized), you may also not use LSE (and save the cost of it).
See below wiki page
How to run an RF application on the STM32WBA without LSE crystal - stm32mcu

 

Regards
Laurent
 

 

[Hitesh2022]

Hello Laurent,

Thank you for your great support.

We have updated the C12 value to 470 nF, and most of the devices are now able to advertise using the P2P example code. However, we are still unable to connect to the devices.

Could you please advise if there are any other settings or hardware points that we should check or update to establish a successful connection?

Your guidance would be highly appreciated.

[Laurent LOUAZON]

Hello,

Have you also removed C16 and C17?
They should not be set for sure.
 

Can you please share exact reference of LSE and HSE xtal used?

 

Regards
Laurent 

[Hitesh2022]

Hello,

 

Not removed both caps, please find below part number for both.

Regards,

Hitesh

[Laurent LOUAZON]

Hello,

HSE.
R2016-32.000-8-F-1010-EXT-TR datasheet says : Cload 8pF, ESR 100Ohms max, C0 : 3.5pF max
It means gmcrit of 2.136mA/V so just limit versus the 2.2mA/V explained in the wiki.
So this should work but C16/C17 must be removed.

 

LSE
I cannot find detailed  datasheet for MU00525-32.768K.
Seems it is a 6pF Cload version so probabaly  C72 and C73 are close from reality.
Wiki is explaining how to check LSE is properly centered or not.
 

Please try at least to remove C16 and C17.

Regards
Laurent

[Hitesh2022]

Hello,

We have removed C16 and C17, but the device is still not able to connect.

We also tried using the crystal from the development board, but unfortunately, the device is still not connecting.

Regards,

Hitesh

[Get Moodie]

Since removing C16 and C17 and trying the development-board crystal didn’t resolve the connection issue, it would be useful to compare the failed and working boards for RF output, power rails, and clock signals. 🔍

[Hitesh2022]

Hello,

The supply rails look correct.

One observation: when we apply 3.0 V instead of 3.3 V, the device starts advertising, but we are still unable to establish a connection.

[Laurent LOUAZON]

can you sent of picture of STM32WBA52 marking?

[Hitesh2022]

Hello,

Attached image of STM32WBA52.