STM32 RTC with HAL libraries

Question

I am working on stm32l053 (nucleo 64) and I want to track time with integrated RTC. Since I am quite new to stm32 development I am using CubeMX and HAL libraries.

My problem is that the time is not changing over time, the HAL_RTC_GetTime() function is always returning time that was configured at the beginning in the MX_RTC_Init() function generated by CubeMX.

Here is my code for testing: Vars:

RTC_TimeTypeDef currTime = {0};

in while

    while (1)
  {
    /* USER CODE END WHILE */

    /* USER CODE BEGIN 3 */
      HAL_RTC_GetTime(&hrtc, &currTime, RTC_FORMAT_BIN);
      char timeBuff[20];
      sprintf(timeBuff,"%d,,,%d...%d\n", currTime.Hours, currTime.Minutes, currTime.Seconds);
      HAL_UART_Transmit(&huart2, timeBuff, sizeof(timeBuff), 100);
      HAL_Delay(1000);


  }

And here is the generated MX_RTC_Init() function:

static void MX_RTC_Init(void)
{

  /* USER CODE BEGIN RTC_Init 0 */

  /* USER CODE END RTC_Init 0 */

  RTC_TimeTypeDef sTime = {0};
  RTC_DateTypeDef sDate = {0};

  /* USER CODE BEGIN RTC_Init 1 */

  /* USER CODE END RTC_Init 1 */
  /** Initialize RTC Only 
  */
  hrtc.Instance = RTC;
  hrtc.Init.HourFormat = RTC_HOURFORMAT_12;
  hrtc.Init.AsynchPrediv = 127;
  hrtc.Init.SynchPrediv = 255;
  hrtc.Init.OutPut = RTC_OUTPUT_DISABLE;
  hrtc.Init.OutPutRemap = RTC_OUTPUT_REMAP_NONE;
  hrtc.Init.OutPutPolarity = RTC_OUTPUT_POLARITY_HIGH;
  hrtc.Init.OutPutType = RTC_OUTPUT_TYPE_OPENDRAIN;
  if (HAL_RTC_Init(&hrtc) != HAL_OK)
  {
    Error_Handler();
  }

  /* USER CODE BEGIN Check_RTC_BKUP */

  /* USER CODE END Check_RTC_BKUP */

  /** Initialize RTC and set the Time and Date 
  */
  sTime.Hours = 10;
  sTime.Minutes = 15;
  sTime.Seconds = 0;
  sTime.TimeFormat = RTC_HOURFORMAT12_PM;
  sTime.DayLightSaving = RTC_DAYLIGHTSAVING_NONE;
  sTime.StoreOperation = RTC_STOREOPERATION_RESET;
  if (HAL_RTC_SetTime(&hrtc, &sTime, RTC_FORMAT_BIN) != HAL_OK)
  {
    Error_Handler();
  }
  sDate.WeekDay = RTC_WEEKDAY_SATURDAY;
  sDate.Month = RTC_MONTH_MAY;
  sDate.Date = 25;
  sDate.Year = 19;

  if (HAL_RTC_SetDate(&hrtc, &sDate, RTC_FORMAT_BIN) != HAL_OK)
  {
    Error_Handler();
  }
  /** Enable the WakeUp 
  */
  if (HAL_RTCEx_SetWakeUpTimer_IT(&hrtc, 5, RTC_WAKEUPCLOCK_CK_SPRE_16BITS) != HAL_OK)
  {
    Error_Handler();
  }
  /* USER CODE BEGIN RTC_Init 2 */

  /* USER CODE END RTC_Init 2 */

}

Serial output is:

10,,,15...0
10,,,15...0
10,,,15...0
10,,,15...0
10,,,15...0
10,,,15...0
10,,,15...0
10,,,15...0
10,,,15...0
10,,,15...0
10,,,15...0
.
.
.

PS. RTC WakeUp is working as expected so the RTC is counting but I guess it is not storing counts in registers.

Answer 1

The solution is to call both GetTime and GetDate at the same time, If you call only GetTime it does not update correctly:

HAL_RTC_GetTime(&hrtc, &currTime, RTC_FORMAT_BIN);
HAL_RTC_GetDate(&hrtc, &currDate, RTC_FORMAT_BIN);

I don't know how they are connected, even more so because GetDate() is run after GetTime() and it still makes difference.

Answer 2

It looks, like clocking for RTC is not enabled (CubeMX generated code sometimes "forgets" to do that). Try adding __HAL_RCC_RTC_ENABLE() to your MX_Init function.

Answer 3

Met the same problem today on my own STM32L072 board. Finally found out LSE is not working, so does the RTC part. The board has a slow start up period because it will switch to LSI after some waiting time.

Change to another board, RTC works fine.

Answer 4

The STM32 RTC locks (freezes) the RTC when you read the time register and un-freezes it when you read the date register. This is done to protect you from the situation where you read the time just before midnight (e.g. 23:59:59) and then the RTC date rolls over to the next day before you read it which would result in an off-by-one-day error.

So read the time register, then read the date register.