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Tomohiro Shirane
Tomohiro Shirane
Associate II
June 7, 2018
Question

STM32 RTC milliseconds setting

  • June 7, 2018
  • 9 replies
  • 7387 views
Posted on June 07, 2018 at 03:50

Hello,

I'm using the STM32 H753 Evaluation board, and trying to set the milliseconds by using HAL_RTC_SetTime function.

However, the HAL_RTC_SetTime function does not change the milliseconds(subseconds) value.

I've read the RTC synchronization chapter in the reference manual, but I don't understand it enough though.

If I would like to set the 400 milliseconds value, should I set the 0x190(= 400 decimal) into SUBFS field in RTC_SHIFTR and set the 0x3E7(= 999 decimal) into PREDIV_S field in RTC_PRER ?

Help would be appreciated.

Thanks.

Shirane.

      This topic has been closed for replies.

      9 replies

      waclawek.jan
      waclawek.jan
      Super User
      June 7, 2018
      Posted on June 07, 2018 at 09:08

      Unless you want to use some nonstandard crystal, no.

      The subsecond register runs in units given by the crystal and asynchronous part of divider (i.e. 1/(fLSE/(PREDIV_A+1)), which in the normal case is equal to 1 second/(PREDIV_S+1) ) and you should set the shift register in the same units.

      In the default case, i.e. PREDIV_A = 0x007F, PREDIV_S = 0x00FF, to shift by 400ms you set SUBFS to 256*0.400≈102.

      JW

        Tomohiro Shirane
        Tomohiro ShiraneAuthor
        Associate II
        June 13, 2018
        Posted on June 13, 2018 at 12:16

        Hello,

        I've tried setting SUBFS field in SHIFT register but I did't get expeced result.

        I've attached my code. The below is code snippet

        --------------------------------------------------------------

        [main.c] <- I've added the code that set SHIFTR after calling MX_RTC_Init();

        /* Initialize all configured peripherals */

        MX_GPIO_Init();

        MX_USART2_UART_Init();

        MX_RTC_Init();

        /* USER CODE BEGIN 2 */

        __HAL_RTC_WRITEPROTECTION_DISABLE(&hrtc);

        hrtc.Instance->SHIFTR = 0x00000190;// 400msec

        __HAL_RTC_WRITEPROTECTION_ENABLE(&hrtc);

        /* USER CODE END 2 */

        [rtc.c] <- set AsynchPredivas 31 andSynchPrediv as 999 in order to set the callendar clock into 1Hz.Currently I'm usingLSI(32KHz) as RTC clock.

        void MX_RTC_Init(void)

        {

        RTC_TimeTypeDef sTime;

        RTC_DateTypeDef sDate;

        /**Initialize RTC Only

        */

        hrtc.Instance = RTC;

        hrtc.Init.HourFormat = RTC_HOURFORMAT_24;

        hrtc.Init.AsynchPrediv = 31;

        hrtc.Init.SynchPrediv = 999;

        hrtc.Init.OutPut = RTC_OUTPUT_DISABLE;

        hrtc.Init.OutPutPolarity = RTC_OUTPUT_POLARITY_HIGH;

        hrtc.Init.OutPutType = RTC_OUTPUT_TYPE_OPENDRAIN;

        if (HAL_RTC_Init(&hrtc) != HAL_OK)

        {

        _Error_Handler(__FILE__, __LINE__);

        }

        /* USER CODE BEGIN RTC_Init 2 */

        /* USER CODE END RTC_Init 2 */

        /**Initialize RTC and set the Time and Date

        */

        sTime.Hours = 0x13;

        sTime.Minutes = 0x22;

        sTime.Seconds = 0x30;

        sTime.DayLightSaving = RTC_DAYLIGHTSAVING_NONE;

        sTime.StoreOperation = RTC_STOREOPERATION_RESET;

        if (HAL_RTC_SetTime(&hrtc, &sTime, RTC_FORMAT_BCD) != HAL_OK)

        {

        _Error_Handler(__FILE__, __LINE__);

        }

        /* USER CODE BEGIN RTC_Init 3 */

        --------------------------------------------------------------

        My question is that:

        • Whereshould I add the code that sets SHIFTR ? Inside ofHAL_RTC_SetTime function ?

        • Is thereany code that I should call(add) around 'hrtc.Instance->SHIFTR ' ?

        Thanks.

        Shirane

        ________________

        Attachments :

        main.c.zip : https://st--c.eu10.content.force.com/sfc/dist/version/download/?oid=00Db0000000YtG6&ids=0680X000006HxVr&d=%2Fa%2F0X0000000az6%2FuL7ROgzBTPUFtaflQ8XCIP8fwLSVomvBhV.B9S88ZXg&asPdf=false

        rtc.c.zip : https://st--c.eu10.content.force.com/sfc/dist/version/download/?oid=00Db0000000YtG6&ids=0680X000006HxVI&d=%2Fa%2F0X0000000ayx%2FtPf1npWlf4sv71iRsgEHSsyjggo0v5xurbKDNeLZu54&asPdf=false
          waclawek.jan
          waclawek.jan
          Super User
          June 13, 2018
          Posted on June 13, 2018 at 12:47

          I've tried setting SUBFS field in SHIFT register but I did't get expeced result.

          What is the expected result and what was your observation?

          JW

            Tomohiro Shirane
            Tomohiro ShiraneAuthor
            Associate II
            June 13, 2018
            Posted on June 13, 2018 at 13:27

            Hi,

            MX_RTC_Init() sets the Hours as 0x13, Minutes as 0x22 and Seconds as 0x30.

            And also, my code sets 400[msec] into 'hrtc.Instance->SHIFTR'.

            In main.c, printf() is called on each 100[msec], that shows the current Hours, Minutes, Seconds and Sub-seconds.

            >> printf('Hours = %d, Minutes = %d, Seconds = %d, SubSeconds = %d\n', time.Hours, time.Minutes, time.Seconds, msec);

            So, the expected result are:

            ----------------------------------------------

            Hours = 13, Minutes = 22, Seconds = 30, SubSeconds = 400

            Hours = 13, Minutes = 22, Seconds = 30, SubSeconds = 500

            Hours = 13, Minutes = 22, Seconds = 30, SubSeconds = 600

            ........

            ----------------------------------------------

            However, the current result are:

            ----------------------------------------------

            Hours = 13, Minutes = 22, Seconds = 30, SubSeconds = 0                   <-  SubSeconds starts with 0.

            Hours = 13, Minutes = 22, Seconds = 30, SubSeconds = 4294676       <-  Strange value ?

            Hours = 13, Minutes = 22, Seconds = 30, SubSeconds = 4294786      <-  Strange value ?

            Hours = 13, Minutes = 22, Seconds = 30, SubSeconds = 4294896      <-  Strange value ?

            Hours = 13, Minutes = 22, Seconds = 30, SubSeconds = 39

            ----------------------------------------------

            Thanks.

            Shirane

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