STM32WL55JC1 Not Waking from Standby via RTC Alarm A

[pavan1]

Hi,

I'm facing an issue with waking the STM32WL55JC1 from Standby mode using RTC Alarm A.

Setup:

• Using LSE as RTC clock source

• RTC and Alarm A are initialized correctly

• Alarm A interrupt works when not entering standby

• Wake-up via RTC Wakeup Timer works fine (standby + timer = success)

Issue:

When I:

1. Clear RTC time and date

2. Set Alarm A to trigger a few seconds ahead

3. Enter Standby mode

4. Wait for wake-up

→ The system does not wake up from Alarm A.

However, if I skip Standby mode, Alarm A fires the interrupt as expected.

Observation:

• RTC Alarm A interrupt is configured and enabled.

• EXTI and NVIC settings are correct.

• I suspect the Alarm A wakeup source isn’t properly enabled or EXTI line isn’t configured before entering standby.
  
  
  

  Request:

  Could you confirm the correct sequence or any missing configuration required for:

  • Enabling Alarm A as a wakeup source from standby

  • Ensuring EXTI line 17 is correctly set before standby

  Let me know if additional register dumps or code snippets are needed.

  Thanks,