STM32 RTC loses one second after each reset

Anyone out there have a suggestion on how to fix this?

Thanks,

Rob

I don't HAL or Cube either, but I think you may want to look at the flag check prior to calling HAL_RTC_Init()

You have:

if (__HAL_PWR_GET_FLAG(PWR_FLAG_SB) == RESET)

I use SPL and I believe the correct check using SPL is:

if(RTC_GetFlagStatus(RTC_FLAG_INITS)==RESET)

I'm thinking the HAL equivalent is probably very similar.

I believe initialization freezes the clock, so it shouldn't be performed every reset.

Hi Tut,

Yes I considered that the initialization might freeze the clock, so I tried calling 

RTC_Init() multiple times consecutively on startup to see if this increased the number of missing seconds. It did not. The problem might have more to do with the section of code that configures the pins and the 32kHz external crystal. Here's my code for that:

void SystemClock_Config_HighSpeed(void)

   RCC_OscInitTypeDef RCC_OscInitStruct;

   __HAL_RCC_PWR_CLK_ENABLE();

   __HAL_PWR_VOLTAGESCALING_CONFIG(PWR_REGULATOR_VOLTAGE_SCALE1);

   RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_HSE|RCC_OSCILLATORTYPE_LSE;

   RCC_ClkInitStruct.ClockType = RCC_CLOCKTYPE_HCLK|RCC_CLOCKTYPE_SYSCLK

   PeriphClkInitStruct.PeriphClockSelection = RCC_PERIPHCLK_I2S|RCC_PERIPHCLK_RTC;

   HAL_RCC_MCOConfig(RCC_MCO1, RCC_MCO1SOURCE_HSE, RCC_MCODIV_4);

   HAL_SYSTICK_Config(HAL_RCC_GetHCLKFreq()/1000);

   HAL_SYSTICK_CLKSourceConfig(SYSTICK_CLKSOURCE_HCLK);

   /* SysTick_IRQn interrupt configuration */

This code is called each time the board is powered up. Would changing this fix the problem?

I have the exact same problem. I am using STM32F103, CubeMX and an external LSE 32.768 KHz crystal with VBat source as a CR2032 Lithium cell. The clock is keeping accurate time while either on power or on backup coin cell. However, I lose around 500 - 600 ms every time the micro is powered up or if I reset the micro using the reset button.

If I hit reset button 100 times, I lose close to a minute.

I do not suspect the crystal as I have taken measurements using an oscilloscope and also I have enabled output on RTC pin and the timing measures perfectly.

It has something to do with the initialization and I have not been able to figure that out so far!

If the RTC is already running, you need no initialization at all.

JW

Ok, so I'm back to trying to get my RTC problem corrected. I appreciate the help I've gotten so far. I'm pursuing Tut's suggestion of checking RTC_FLAG_INITS flag before configuring the RTC external clock. Tut uses the code:

if(RTC_GetFlagStatus(RTC_FLAG_INITS)==RESET) {

This appears to be from the Standard Peripheral Libraries. Since I'm fairly new to the STM32 I've gotten started with the HAL libraries. I'm having trouble finding an equivalent function in the HAL libraries to RTC_GetFlagStatus() function. Does anyone know the function to use? Again, I need to check the RTC_FLAG_INITS flag using the HAL libraries.

Also if anyone can point me to an example project or documentation showing properconfiguring the RTC clock that would be a huge help! All the documentation I've seen so far seems to skip this crucial bit of initialization code

Thanks again,

Rob

After some trial and error I came up with a solution that seems to work. The key piece Iseemed to be missing was this:

You SHOULD configure the peripheral clock for the RTC every time the themicrocontroller resets. I.e. the following code:

RCC_PeriphCLKInitTypeDef PeriphClkInitStruct;
PeriphClkInitStruct.PeriphClockSelection = RCC_PERIPHCLK_RTC;
 PeriphClkInitStruct.RTCClockSelection = RCC_RTCCLKSOURCE_LSE;
 HAL_RCCEx_PeriphCLKConfig(&PeriphClkInitStruct);�?�?�?�?

The aboveconfiguration doesn't seem to save after a power on reset in the backup domain

You SHOULD NOT need to reconfigure the 32kHz oscillator after each reset. I.e. the following code:

RCC_OscInitTypeDef RCC_OscInitStruct; 
 RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_LSE; 
 RCC_OscInitStruct.LSEState = RCC_LSE_ON;
 HAL_RCC_OscConfig(&RCC_OscInitStruct);�?�?�?�?

In the end I settled on the following RTC_INIT() function, which seems to work in my testing so far:

void RTC_Init(void)
{ 
 RTC_HandleTypeDef hrtc;
 hrtc.Instance = RTC;
 
 /* Read the Back Up Register 0 Data */
 if(HAL_RTCEx_BKUPRead(&hrtc, RTC_BKP_DR0) != 0x32F2) 
 {
 //Only execute this code if the RTC has not previously been configured
 //**INITIALIZE 32kHz CLOCK*********************************
 RCC_OscInitTypeDef RCC_OscInitStruct; 
 RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_LSE; 
 RCC_OscInitStruct.LSEState = RCC_LSE_ON;
 HAL_RCC_OscConfig(&RCC_OscInitStruct);
 //**END INITIALIZE 32kHz CLOCK************************************************ 
 
 /* Initialize RTC and set the Time and Date */
 hrtc.Init.HourFormat = RTC_HOURFORMAT_24;
 hrtc.Init.AsynchPrediv = 127;
 hrtc.Init.SynchPrediv = 255;
 hrtc.Init.OutPut = RTC_OUTPUT_DISABLE;
 hrtc.Init.OutPutPolarity = RTC_OUTPUT_POLARITY_HIGH;
 hrtc.Init.OutPutType = RTC_OUTPUT_TYPE_OPENDRAIN;
 HAL_RTC_Init(&hrtc); 
 
 RTC_TimeTypeDef sTime;
 RTC_DateTypeDef sDate; 
 
 /* Configure RTC Calendar */
 sTime.Hours = 0;
 sTime.Minutes = 0;
 sTime.Seconds = 0;
 sTime.SubSeconds = 0;
 sTime.TimeFormat = RTC_HOURFORMAT12_AM;
 sTime.DayLightSaving = RTC_DAYLIGHTSAVING_NONE;
 sTime.StoreOperation = RTC_STOREOPERATION_RESET;
 HAL_RTC_SetTime(&hrtc, &sTime, FORMAT_BCD);
 sDate.WeekDay = RTC_WEEKDAY_MONDAY;
 sDate.Month = RTC_MONTH_JANUARY;
 sDate.Date = 1;
 sDate.Year = 1;
 HAL_RTC_SetDate(&hrtc, &sDate, FORMAT_BCD);
 /*##-3- Writes a data in a RTC Backup data Register0 #####################*/
 HAL_RTCEx_BKUPWrite(&hrtc,RTC_BKP_DR0,0x32F2); 
 } 
}�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?

Just wanted to point out that there still doesn't seem to be any workable code examples for configuring the RTC with the HAL libraries. Seems funny that such a basic feature is still missing

-Rob

Hello All,

I confirm this issue for HAL RTC and highlighted internally to developer team for fix.

Sorry for such inconvenience.

Best Regards,

Imen