STM32L151 RTC Summary

1. IO port related to RTC: PC13 (TAMPER-RTC) cannot be set to GPIO_Mode_AN state, otherwise it will not enter the RTC interrupt. (It can be set to GPIO_Mode_IN).

2. RTC_WakeUpCmd(DISABLE) is required before setting the RTC clock. This sentence is not in the official example. If this sentence is not there, the RTC will only be reset when the power is turned on again, and the RTC will not be reset when the program is run again.

3. Before setting the RTC timer wake-up interrupt, be sure to clear the corresponding interrupt, otherwise the phenomenon will be that the RTC interrupt can sometimes be entered but sometimes cannot be entered.

 RTC_ClearITPendingBit(RTC_IT_WUT);

  RTC_ITConfig(RTC_IT_WUT, ENABLE);

 4. When the RTC periodic interrupt wakes up the CPU from stop mode, the Wake-Up flag must be cleared, otherwise the RTC interrupt can only be entered once and cannot be entered subsequently.

 if(PWR_GetFlagStatus(PWR_FLAG_WU) != RESET) // Check if the wakeup flag is set 

 {

PWR_ClearFlag(PWR_FLAG_WU);

 }  

Unresolved issues: After the RTC wakes up the CPU, if MSI is configured as the clock source, when entering low power consumption again, the power consumption remains at 60-70ua, and the reason is unknown; when HSE is used as the interrupt source, the RTC interrupt will no longer be entered after three or four times. Currently, HSI is used as the interrupt source after RTC wakes up.