STM32WBA family use of stack BLE without LSE (with LSI2)

[Wladimiro_Gaiotti]

Hi to all!

We are developing a low-cost application, with in mind STM32WBA52KE, which use a 32 pin package.

Due to short number of pin, we would use pin 12 and 13 as GPIO, so we should not use the LSE.

Is it possible to manage the BLE stack without LSE, using LSI2? If yes, which kind of limitation we will have?

I can't find the right answer on documentation, can you help me?

Thank you very much in advance.

[STTwo-32 · Accepted solution]

Hello @Wladimiro_Gaiotti and welcome to the ST Community.

Yes, you can implement a BLE application using the STM32WBA52 without LSE. In this case, you will have to use HSE/1000 as clock source for the radio sleep timer clock. As mentioned on the release note of STM32CubeWBA package v1.4.1, LSI2 is not supported as clock source for the radio sleep timer clock.  Using HSE also will limit you on Low power modes to sleep mode. 

Best Regards.

STTwo-32

[rajdeep_01]

Hi @STTwo-32,

- Implemented near similar case, that not used LSE, results issue in BLE connection.
- As BLE requires Radio Sleep Timer Clock, for which two options available:
Option-1. HSE/1000: Implemented, tested and found that BLE advertisement works but connection not works.
Option-2. LSE: Implemented, tested and found that BLE advertisement and connection works perfectly.
Seems, LSE is mandatory for BLE operations.

- Further, in reference manual mentioned that LSI2 is available for STM32WBA54/55xx devices,
Means, not available for STM32WBA52xx devices:

- Can you please provide guidance, related to which source require for Radio-Sleep-Timer-Clock,
And how to make BLE working properly, is that further configuration requires?

Thanks

[STTwo-32]

Hello @rajdeep_01 

Maybe my first answer was not clear. I've updated my answer with more details that you may check.

Best Regards.

STTwo-32

[rajdeep_01]

Hi @STTwo-32,

Thanks for quick reply,
But unfortunately, with HSE/1000 as source, BLE not working properly, in this case, application able to capture BLE advertisement data but not able to connect over BLE, every time connection timeout occurs, scenario is reproduceable,
only upon LSE as radio-sleep-time clock-source working properly,
I have tried multiple times with different boards, applications & mobiles,
tested with Nucleo-WBA52CG, App ST-BLE-Toolbox.

It will be really helpful in case, you will able to provide a working example where HSE/1000 configured for Nucleo-WBA52CG, you can use existing examples, such as p2p_server_ota where LSE clock used and only modify related to HSE/1000 and test.

Thanks.