STM32WB55 freezing when returned from STOP2 after RTC wakeup

fo · ‎2025-09-05

Hello,

I modified the BLE Beacon example to send 5 beacon packets and then enter into the STOP2 mode. It is possible to wake-up and resend 5 packets when a button is activated. However, when the time is set, the MCU wakes-up, and freeze.

The function UTIL_LPM_EnterLowPower() is used for entering low-power, and HAL_RTCEx_SetWakeUpTimer_IT() is used for setting the wake-up time. a few seconds are used as wake-up time. The wake-up is only verified by monitoring the current consumption increased from few µA to approx. 2.5mA after the time is elapsed. Beside that turning on one of the LEDs has been implemented in the RTC wake-up interrupt routine, and one just after the __WFI without it's being triggered.

It has not been possible to debug, as the debug does not return until the execution is paused, and when it's paused the PC points on the next line of the __WFI instruction.

Do you have any ideas of what the reason can be, or any suggestion on debugging?

Best regards,
Fatih

STTwo-32 · ‎2025-09-22

Hello @fo

Could you please try to use a HW timer for the walke up instead of using the RTC. I think there is not an accuracy problem since the LPM is based on the RTC. So, i think this should help you.

Best Regards.

STTwo-32

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