STM32WB55RG: Instability of LSE clock on Nucleo board

[apous.1]

Hi,

I am using the Nucleo WB55 board that has a STM32WB55RGV6 MCU to develop an application.

I see instabilities in bluetooth by default when I am using the LSE clock as RfWkUpClock of the BLE that are leading to the BLE core crashing.

Those instabilities disappear when I disable the use of the LSE clock and replace it by the HSE clock. That is though not a long term solution for me as the difference of power consumption is quite consequent.

I did probe the LSE clock on the LSCO pin of the MCU and got the attached measurement.

Why is the LSE clock so unstable?

Is there any way to make the BLE more robust while still using the LSE clock?

Best regards,

Antoine Poussart

[Remy ISSALYS]

Hello,

According to the errata sheet ES0394 some GPIO can disturbs the LSE clock, these GPIO are PC13 and PH3:

• The PC13 port toggling disturbs the LSE clock. It may not be usable when LSE is used.
• Toggling on the PH3 port disturbs the LSE clock. The PH3 port may not be usable at the same time as LSE is used. 

Which STM32CubeWB firmware version are you using ?

Best Regards

[apous.1]

Dear,

Thank you for your answer.

That was a good insight but unfortunately both PC13 and PH3 are stable values that do not toggle.

I am currently using STM32CubeWB 1.13.0 but I saw the same issue with 1.13.2, 1.13.3 and 1.14.0.

Best regards,

Antoine Poussart

[Remy ISSALYS]

Hello,

I recommend to you to use the latest firmware version v1.14.1. Are you using the SMPS ? Can you check the value of the following define in app_conf.h ? And how do you power the board ?

#if defined(STM32WB5Mxx)
  #define CFG_BLE_LSE_SOURCE  (SHCI_C2_BLE_INIT_CFG_BLE_LSE_NOCALIB | SHCI_C2_BLE_INIT_CFG_BLE_LSE_MOD5MM_DEV)
#else
  #define CFG_BLE_LSE_SOURCE  (SHCI_C2_BLE_INIT_CFG_BLE_LSE_NOCALIB | SHCI_C2_BLE_INIT_CFG_BLE_LSE_OTHER_DEV)
#endif

Best Regards