STWINBX1 loses RTC at poweroff?

[Old_Geezer]

Hi

I have found that the STWINBX1 loses RTC at poweroff (or does CubeMX write code to reset RTC at poweron? there is a ticket on that) so that I have to battery-power it on, connect usb, update RTC and then disconnect while still on in order to log without "2001-01-01 00:01". 

Its LiPo battery is connected and above 90%

Is there a remedy?

[SofLit]

Hello, 

---

@Old_Geezer wrote:

or does CubeMX write code to reset RTC at poweron?

---

Check if you don't configure the the time and date at each power on. Check out this example:

https://github.com/STMicroelectronics/STM32CubeL4/tree/master/Projects/STM32L476G-EVAL/Examples/RTC/RTC_Calendar

You need to configure the Time/Date one and save that status in the Buck up register and at each power on you check this status, if the time/date was configured you escape the time/date settings:

RTC_CalendarConfig() implementation:

static void RTC_CalendarConfig(void)
{
  RTC_DateTypeDef sdatestructure;
  RTC_TimeTypeDef stimestructure;

  /*##-1- Configure the Date #################################################*/
  /* Set Date: Tuesday February 18th 2014 */
  sdatestructure.Year = 0x14;
  sdatestructure.Month = RTC_MONTH_FEBRUARY;
  sdatestructure.Date = 0x18;
  sdatestructure.WeekDay = RTC_WEEKDAY_TUESDAY;
  
  if(HAL_RTC_SetDate(&RtcHandle,&sdatestructure,RTC_FORMAT_BCD) != HAL_OK)
  {
    /* Initialization Error */
    Error_Handler(); 
  } 
  
  /*##-2- Configure the Time #################################################*/
  /* Set Time: 02:00:00 */
  stimestructure.Hours = 0x02;
  stimestructure.Minutes = 0x00;
  stimestructure.Seconds = 0x00;
  stimestructure.TimeFormat = RTC_HOURFORMAT12_AM;
  stimestructure.DayLightSaving = RTC_DAYLIGHTSAVING_NONE;
  stimestructure.StoreOperation = RTC_STOREOPERATION_RESET;
  
  if(HAL_RTC_SetTime(&RtcHandle,&stimestructure,RTC_FORMAT_BCD) != HAL_OK)
  {
    /* Initialization Error */
    Error_Handler(); 
  }
  
  /*##-3- Writes a data in a RTC Backup data Register0 #######################*/
  HAL_RTCEx_BKUPWrite(&RtcHandle,RTC_BKP_DR0,0x32F2);  
}

-> it sets the value 0x32F2 in the BKP registers after configuring the calendar.

That will be checked later on at power up.

  /*##-2- Check if Data stored in BackUp register1: No Need to reconfigure RTC#*/
  /* Read the Back Up Register 1 Data */
  if (HAL_RTCEx_BKUPRead(&RtcHandle, RTC_BKP_DR1) != 0x32F2)
  {
    /* Configure RTC Calendar */
    RTC_CalendarConfig();
  }
  else
  {

 Hope that answers your question.

[Old_Geezer]

Hope it does, bc it's running your DATALOG2v2.2.0 demo, downloaded and flashed "as is" :)

[SofLit]

Sorry I don't have idea about this demo even about this STWINBX1 board but the concept is the same as long as this box is based on a STM32 MCU ;)

[Old_Geezer]

Sorry, but your example only results in the clock being set to 240218 00:00.

So either my implementation of your code is bad or the MCU has no RTC power.

Below is main() of my altered DATALOG2 demo.

int main(void)
{
  // System initialization
RTC_HandleTypeDef RtcHandle;
    RtcHandle.Instance = RTC;
  SysInit(FALSE);
  if (HAL_RTCEx_BKUPRead(&RtcHandle, RTC_BKP_DR1) != 0x32F2)
    {
      /* Configure RTC Calendar */
      RTC_CalendarConfig();
    }
    else
    {
    }
  tx_kernel_enter();
  while (1);
}

[SofLit]

Hello,

The code I provided is taken from this example and nothing wrong in it: form https://github.com/STMicroelectronics/STM32CubeL4/tree/master/Projects/STM32L476G-EVAL/Examples/RTC/RTC_Calendar

You need to have VBAT pin powered on (to backup the time and the backup registers) while the board is powered off. This is the idea.

[Old_Geezer]

Well, maybe you can find someone who can confirm whether VBAT is connected uninterrupted to battery on this board. I can't, not that proficient. In the user's manual are two links (in blue) to further details but those are dead:  

I was however able to google the schematic:

https://www.st.com/resource/en/schematic_pack/steval-stwinbox1-schematic.pdf

[SofLit · Accepted solution]

According to the schematics you attached, VBAT pin is hardwired to VDD_uC and not to a dedicated battery cell. So if you lose the power on VDD_uC you will lose the Time/date. So you need to keep VDD_uC powred on.

[Old_Geezer]

Well, that board is a (likely multilayered) ST board, so either you or I will have to file a report if this is to be fixed in a future version.

[SofLit]

I think connecting VBAT to VDD was an option of the design I think for simplification and this is something we can see in many ST boards like Disco board for example.

I've already escalated this remark a moment ago .. I don't know if it will be taken in consideration or not.