How to wake-up from Standby mode with RTC?

Junde · ‎2023-12-25

Hi guys,

I want to wake up my MCU every 10 sec. And I had to write some code as follows:

  if(__HAL_PWR_GET_FLAG(PWR_FLAG_SB) != RESET) {
      __HAL_PWR_CLEAR_FLAG(PWR_FLAG_SB);
      sprintf((char*)uartBuf, "wakeup from standby\n");
      HAL_UART_Transmit(&huart1, (uint8_t*)uartBuf, strlen((char*)uartBuf), 100);
      
      HAL_RTC_GetTime(&hrtc, &rtcTime, RTC_FORMAT_BIN);
      rtcAlarm.AlarmTime.Hours = (rtcTime.Hours + (rtcTime.Minutes + (rtcTime.Seconds + 10) / 60) / 60) % 24;
      rtcAlarm.AlarmTime.Minutes = (rtcTime.Minutes + (rtcTime.Seconds + 10) / 60) % 60;
      rtcAlarm.AlarmTime.Seconds = (rtcTime.Seconds + 10) % 60;
      HAL_RTC_SetAlarm_IT(&hrtc, &rtcAlarm, RTC_FORMAT_BIN);
      
      sprintf((char*)uartBuf, "cur time:  %02d:%02d:%02d\n", rtcTime.Hours, rtcTime.Minutes, rtcTime.Seconds);
      HAL_UART_Transmit(&huart1, (uint8_t*)uartBuf, strlen((char*)uartBuf), 100);
      sprintf((char*)uartBuf, "set alarm: %02d:%02d:%02d\n", rtcAlarm.AlarmTime.Hours, rtcAlarm.AlarmTime.Minutes, rtcAlarm.AlarmTime.Seconds);
      HAL_UART_Transmit(&huart1, (uint8_t*)uartBuf, strlen((char*)uartBuf), 100);
      
      sprintf((char*)uartBuf, "Do User Tasks...\n");
      HAL_UART_Transmit(&huart1, (uint8_t*)uartBuf, strlen((char*)uartBuf), 100);
      HAL_Delay(500);

      HAL_PWR_EnterSTANDBYMode();
  } else {  
      sprintf((char*)uartBuf, "\n\nRTC init\n");
      HAL_UART_Transmit(&huart1, (uint8_t*)uartBuf, strlen((char*)uartBuf), 100);
      
      //MX_RTC_Init();
      hrtc.Instance = RTC;
      hrtc.Init.AsynchPrediv = RTC_AUTO_1_SECOND;
      HAL_RTC_Init(&hrtc);

      rtcTime.Hours = 0;
      rtcTime.Minutes = 0;
      rtcTime.Seconds = 0;
      HAL_RTC_SetTime(&hrtc, &rtcTime, RTC_FORMAT_BIN);

      rtcAlarm.Alarm = RTC_ALARM_A;
      rtcAlarm.AlarmTime.Hours = 0;
      rtcAlarm.AlarmTime.Minutes = 0;
      rtcAlarm.AlarmTime.Seconds = 10;
      HAL_RTC_SetAlarm_IT(&hrtc, &rtcAlarm, RTC_FORMAT_BIN);

      HAL_PWR_EnterSTANDBYMode();
  }

The output is as below:

// I add the timestamp for reference
[10:45:49.103] RTC init
[10:46:00.218] wakeup from standby
[10:46:02.733] cur time:  15:53:36
[10:46:02.733] set alarm: 15:53:46
[10:46:02.733] Do User Tasks...
[10:46:02.733] wakeup from standby
[10:46:05.236] cur time:  15:53:36
[10:46:05.236] set alarm: 15:53:46
[10:46:05.236] Do User Tasks...
[10:46:05.236] wakeup from standby
[10:46:07.753] cur time:  15:53:36
[10:46:07.753] set alarm: 15:53:46
[10:46:07.753] Do User Tasks...
[10:46:07.753] wakeup from standby

From the output, we can see the MCU was waked up every 2-3sec, NOT 10 sec. And the cur time is always 15:53:36, can't be added.

I am not clear why this happened, may there be something wrong with the schematic or just the code?

The above unexpected output is received when both the VCC3.3V and the Battery are 3.3V. (The result is the same when taking off the battery.)

I have more questions: Can the MCU work well just with the VDD power or just with the VBAT power?

Thanks for your help.

MM..1 · ‎2023-12-26

In firmwre resource folder you can found examples , check your code with this. STM32CubeF1/Projects/STM32F103RB-Nucleo/Examples at master · STMicroelectronics/STM32CubeF1 · GitHub

And maybe your primary issue is debug with enabled low power mode debuging = waking MCU here isnt real standart. Disable it in config and power off all power sources before next testing.

Junde · ‎2023-12-28

Hi @MM..1

Thanks for your reply.

I already read all the source code about RTC and standby. And my code is changed from the examples.

Now I can be sure the RTC alarm setting is correct because it works well when I disable the standby mode.

There must be some bugs in my "standby" code or the schematic.

MM..1 · ‎2023-12-28

Try add GetDATE dummy ... hal locking issue