What is the STM32WB55's HSE with LSI configuration workflow?

[Mecanix]

Greetings friends

I'm trying to find the workflow to effectively set-up a STM32WB55 to work with a HSE and LSI (no LSE) and just can't seem to be able make this work while others claims it works fine. Everything works perfectly with HSE and LSE using the p2pserver example however as soon as I set the CubeIDE's clock settings to LSI the device refuse to connect.

I've read in another thread that you are required to set HSE/1024. How do you achieve this? In CubeIDE or this is a hardcoded function somewhere?

Thanks

[Ons KOOLI]

Hi Mecanix,

Can you please explain more your claim?

I think you want to replace the LSE clock (which is powering the RTC/LCD source) by LSI. Can you explain what are the changes you exactly made? What do you mean by it didn't work ? Does this mean that there are compilation errors or the compilation is good but the program does not run properly.

Concerning the require you found :

'I've read in another thread that you are required to set HSE/1024.' Can you provide the source for this information ?

Best Regards,

Ons.

[Mecanix]

Hi Ons, thanks for investigating into this. Firstly I am not stranded and fully operational, this enquiry is simply on a research basis (tests), neither bug related.

Can you please explain more your claim? I think you want to replace the LSE clock (which is powering the RTC/LCD source) by LSI. Can you explain what are the changes you exactly made?

In short; I'm trying to save real estate on a rather high density custom board design by physically removing the LSE and two caps (if feasible).

Detail: I've recently read from a thread that it is possible to clock the WB55 by simply using a HSE and LSI. To test that I've disabled the LSE from within CubeIDE and set the RTC to run on LSI1. With this set-up I can advertise BLE however it is impossible to connect to the device with this same set-up.

What do you mean by it didn't work ? Does this mean that there are compilation errors or the compilation is good but the program does not run properly.

The application run perfectly fine with the manufacturer's recommended HSE & LSE. My tests only fail when trying this HSE & LSI hack/set-up that other members claimed working, just didn't worked for me or I'm completely missing the workflow. I did not see any compilation errors after disabling the LSE and enabling LSI.

Concerning the require you found : 'I've read in another thread that you are required to set HSE/1024.' Can you provide the source for this information ?

Sure. See [here] where members are discussing this setup. Not entirely sure how and where I would go about writing a function to divide the HSE down to 1024. I see a relevant input in CubeIDE's clock page however in my case this is set and locked to /1000 for some strange reason.

[Mecanix]

Side note/update: since OP I've had a discussion with our STM part supplier late today and who is investigating the possibility to supply us with the STM32WB55MMG, as per his recommendation for our application. We don't need many (<1,000) so I wouldn't spend too much time and effort testing this HSE & LSI "un-supported" solution just yet, although it would still be invaluable information if yourself or anyone knows how this could be achieved with code (concise workflow).

Hopefully I'll hear back from him tomorrow on rfq/availability and a few samples. In a meantime I'm all ears if anyone knows how to hack that LSI ;)

[Ons KOOLI]

Hi Mecanix,

I checked the BLE_p2pServer application.

The clocks used are HSE and LSE. I changed the LSE clock to LSI in CubeIDE/MX and the example still works perfectly. Well, I used the P-NUCLEO-WB55.Nucleo board and the ST BLE sensor app. Maybe you have misconfigured your hardware, since you are using your custom board.

Best Regards,

Ons.

[Ons KOOLI]

Hi Mecanix,

Any updates on this question ?

Best Regards,

Ons.