stm32h7 rtc resets after power down (vbat is connected) - stm32

Question

I am using a stm32h753 and stm32cubemx, and trying to run the RTC module on VBAT. To do this I have connected a battery to the MCU. RTC is connected to LSE. Next, I set the RTC in my code and then I disconnect the MCU from power source, and then reconnect it again. Based on the documentation, this should automatically switch the RTC power source from VDD to VBAT.
I have commented the MX_RTC_Init() in the startup, so that RTC is not reset when the MCU restart.
Below are the code for system clock config, RTC Init, and the code to read the RTC registers after reset.
void SystemClock_Config(void)
{
RCC_OscInitTypeDef RCC_OscInitStruct = {0};
RCC_ClkInitTypeDef RCC_ClkInitStruct = {0};
RCC_PeriphCLKInitTypeDef PeriphClkInitStruct = {0};
/** Supply configuration update enable
*/
HAL_PWREx_ConfigSupply(PWR_LDO_SUPPLY);
/** Configure the main internal regulator output voltage
*/
__HAL_PWR_VOLTAGESCALING_CONFIG(PWR_REGULATOR_VOLTAGE_SCALE1);
while(!__HAL_PWR_GET_FLAG(PWR_FLAG_VOSRDY)) {}
/** Configure LSE Drive Capability
*/
HAL_PWR_EnableBkUpAccess();
__HAL_RCC_LSEDRIVE_CONFIG(RCC_LSEDRIVE_LOW);
/** Macro to configure the PLL clock source
*/
__HAL_RCC_PLL_PLLSOURCE_CONFIG(RCC_PLLSOURCE_HSE);
/** Initializes the CPU, AHB and APB busses clocks
*/
RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_HSE|RCC_OSCILLATORTYPE_LSE;
RCC_OscInitStruct.HSEState = RCC_HSE_ON;
RCC_OscInitStruct.LSEState = RCC_LSE_ON;
RCC_OscInitStruct.PLL.PLLState = RCC_PLL_ON;
RCC_OscInitStruct.PLL.PLLSource = RCC_PLLSOURCE_HSE;
RCC_OscInitStruct.PLL.PLLM = 1;
RCC_OscInitStruct.PLL.PLLN = 84;
RCC_OscInitStruct.PLL.PLLP = 2;
RCC_OscInitStruct.PLL.PLLQ = 4;
RCC_OscInitStruct.PLL.PLLR = 2;
RCC_OscInitStruct.PLL.PLLRGE = RCC_PLL1VCIRANGE_3;
RCC_OscInitStruct.PLL.PLLVCOSEL = RCC_PLL1VCOWIDE;
RCC_OscInitStruct.PLL.PLLFRACN = 0;
if (HAL_RCC_OscConfig(&RCC_OscInitStruct) != HAL_OK)
{
Error_Handler();
}
/** Initializes the CPU, AHB and APB busses clocks
*/
RCC_ClkInitStruct.ClockType = RCC_CLOCKTYPE_HCLK|RCC_CLOCKTYPE_SYSCLK
|RCC_CLOCKTYPE_PCLK1|RCC_CLOCKTYPE_PCLK2
|RCC_CLOCKTYPE_D3PCLK1|RCC_CLOCKTYPE_D1PCLK1;
RCC_ClkInitStruct.SYSCLKSource = RCC_SYSCLKSOURCE_PLLCLK;
RCC_ClkInitStruct.SYSCLKDivider = RCC_SYSCLK_DIV1;
RCC_ClkInitStruct.AHBCLKDivider = RCC_HCLK_DIV2;
RCC_ClkInitStruct.APB3CLKDivider = RCC_APB3_DIV2;
RCC_ClkInitStruct.APB1CLKDivider = RCC_APB1_DIV4;
RCC_ClkInitStruct.APB2CLKDivider = RCC_APB2_DIV4;
RCC_ClkInitStruct.APB4CLKDivider = RCC_APB4_DIV2;
if (HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_2) != HAL_OK)
{
Error_Handler();
}
PeriphClkInitStruct.PeriphClockSelection = RCC_PERIPHCLK_RTC|RCC_PERIPHCLK_USART3
|RCC_PERIPHCLK_SPI1|RCC_PERIPHCLK_SDMMC
|RCC_PERIPHCLK_ADC;
PeriphClkInitStruct.PLL2.PLL2M = 1;
PeriphClkInitStruct.PLL2.PLL2N = 25;
PeriphClkInitStruct.PLL2.PLL2P = 4;
PeriphClkInitStruct.PLL2.PLL2Q = 2;
PeriphClkInitStruct.PLL2.PLL2R = 2;
PeriphClkInitStruct.PLL2.PLL2RGE = RCC_PLL2VCIRANGE_3;
PeriphClkInitStruct.PLL2.PLL2VCOSEL = RCC_PLL2VCOMEDIUM;
PeriphClkInitStruct.PLL2.PLL2FRACN = 0;
PeriphClkInitStruct.SdmmcClockSelection = RCC_SDMMCCLKSOURCE_PLL;
PeriphClkInitStruct.Spi123ClockSelection = RCC_SPI123CLKSOURCE_PLL;
PeriphClkInitStruct.Usart234578ClockSelection = RCC_USART234578CLKSOURCE_D2PCLK1;
PeriphClkInitStruct.AdcClockSelection = RCC_ADCCLKSOURCE_PLL2;
PeriphClkInitStruct.RTCClockSelection = RCC_RTCCLKSOURCE_LSE;
if (HAL_RCCEx_PeriphCLKConfig(&PeriphClkInitStruct) != HAL_OK)
{
Error_Handler();
}
}
This is the RTC Init code
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};
RTC_AlarmTypeDef sAlarm = {0};
/* USER CODE BEGIN RTC_Init 1 */
/* USER CODE END RTC_Init 1 */
/** Initialize RTC Only
*/
hrtc.Instance = RTC;
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;
hrtc.Init.OutPutRemap = RTC_OUTPUT_REMAP_NONE;
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 = 0x0;
sTime.Minutes = 0x0;
sTime.Seconds = 0x0;
sTime.DayLightSaving = RTC_DAYLIGHTSAVING_NONE;
sTime.StoreOperation = RTC_STOREOPERATION_RESET;
if (HAL_RTC_SetTime(&hrtc, &sTime, RTC_FORMAT_BCD) != HAL_OK)
{
Error_Handler();
}
sDate.WeekDay = RTC_WEEKDAY_MONDAY;
sDate.Month = RTC_MONTH_JANUARY;
sDate.Date = 0x1;
sDate.Year = 0x0;
if (HAL_RTC_SetDate(&hrtc, &sDate, RTC_FORMAT_BCD) != HAL_OK)
{
Error_Handler();
}
/** Enable the Alarm A
*/
sAlarm.AlarmTime.Hours = 0x0;
sAlarm.AlarmTime.Minutes = 0x20;
sAlarm.AlarmTime.Seconds = 0x0;
sAlarm.AlarmTime.SubSeconds = 0x0;
sAlarm.AlarmTime.DayLightSaving = RTC_DAYLIGHTSAVING_NONE;
sAlarm.AlarmTime.StoreOperation = RTC_STOREOPERATION_RESET;
sAlarm.AlarmMask = RTC_ALARMMASK_DATEWEEKDAY|RTC_ALARMMASK_HOURS;
sAlarm.AlarmSubSecondMask = RTC_ALARMSUBSECONDMASK_ALL;
sAlarm.AlarmDateWeekDaySel = RTC_ALARMDATEWEEKDAYSEL_DATE;
sAlarm.AlarmDateWeekDay = 0x1;
sAlarm.Alarm = RTC_ALARM_A;
if (HAL_RTC_SetAlarm_IT(&hrtc, &sAlarm, RTC_FORMAT_BCD) != HAL_OK)
{
Error_Handler();
}
/** Enable the Alarm B
*/
sAlarm.AlarmTime.Minutes = 0x40;
sAlarm.Alarm = RTC_ALARM_B;
if (HAL_RTC_SetAlarm_IT(&hrtc, &sAlarm, RTC_FORMAT_BCD) != HAL_OK)
{
Error_Handler();
}
/* USER CODE BEGIN RTC_Init 2 */
/* USER CODE END RTC_Init 2 */
}
this is the code I use after startup to read the rtc register vallues:
HAL_RTC_GetTime(&hrtc, &sTime, RTC_FORMAT_BIN);
HAL_RTC_GetDate(&hrtc, &sDate, RTC_FORMAT_BIN);
float subSecondsFloat = ( 255 - sTime.SubSeconds );
subSecondsFloat = (subSecondsFloat /255);
subSecondsFloat = (subSecondsFloat * 1000);
year = (uint32_t) (sDate.Year);
month = (uint32_t) (sDate.Month);
day = (uint32_t) (sDate.Date);
hours = (uint32_t) (sTime.Hours);
minutes = (uint32_t) (sTime.Minutes);
seconds = (uint32_t) (sTime.Seconds);
subseconds = (uint32_t) (subSecondsFloat);
sprintf(usartSendBuffer,"\n%lu,%lu,%lu,%lu,%lu,%lu,%lu\n", year,month,day,hours, minutes,seconds,subseconds);
printf(usartSendBuffer);
When I disconnect the MCU from power source, and reconnect it to power source, the above code gives the following results (RTC register values) after a power reset:
159,10,9,32,51,51,4294967295
So the RTC is reset somewhere in the MCU reset. Considering that I have disabled the MX_RTC_Init(), I do not know where the RTC is reset.
sorry if the question is elementary, I am really new to this field.
I greatly appreciate any help, thank you.
Best regards,
Vouria

Answer 1

You need to check backup state.
Refer to the below code.
it is example for calendar using STM32 series.
/**
* #brief RTC Initialization Function
* #param None
* #retval None
*/
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_24;
hrtc.Init.AsynchPrediv = 127; ///?// 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;
hrtc.Init.OutPutRemap = RTC_OUTPUT_REMAP_NONE;
if (HAL_RTC_Init(&hrtc) != HAL_OK)
{
Error_Handler();
}
/* USER CODE BEGIN Check_RTC_BKUP */
/*##-1- Check if Data stored in BackUp register1: No Need to reconfigure RTC#*/
/* Read the Back Up Register 1 Data */
if (HAL_RTCEx_BKUPRead(&hrtc, RTC_BKP_DR0) != RTC_BKUP_DEFINE_CODE)
{
// Clear Backup registor : recover to current RTC information
// Set to Time/Date from current Time/Date
// Write a data in ad RTC Backup data register
HAL_RTCEx_BKUPWrite(&hrtc, RTC_BKP_DR0, RTC_BKUP_DEFINE_CODE);
} else
{
// Only read time and date
HAL_RTC_GetTime(&hrtc, Time, Format);
HAL_RTC_GetDate(&hrtc, Date, Format);
}
/* USER CODE END Check_RTC_BKUP */
/* USER CODE BEGIN RTC_Init 2 */
/* USER CODE END RTC_Init 2 */
}

Answer 2

Just to confirm: I cannot find an example of using VBat to maintain the RTC Clock either;
Just a tip though: The HAL RTC clock intialisation sets the clock and calendar registers to zero, which is a bit quaint. You must remove this from the initialisation code otherwise every time you boot you set the clock to zero:
/**
* #brief RTC Initialization Function
* #param None
* #retval None
*/
static void MX_RTC_Init(void)
{
/* USER CODE BEGIN RTC_Init 0 */
/* USER CODE END RTC_Init 0 */
#if TIME_DATE_SET_ON_BOOT == 1
RTC_TimeTypeDef sTime = {0};
RTC_DateTypeDef sDate = {0};
#endif
/* USER CODE BEGIN RTC_Init 1 */
/* USER CODE END RTC_Init 1 */
/** Initialize RTC Only
*/
hrtc.Instance = RTC;
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;
hrtc.Init.OutPutRemap = RTC_OUTPUT_REMAP_NONE;
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
*/
#if TIME_DATE_SET_ON_BOOT == 1
sTime.Hours = 0x0;
sTime.Minutes = 0x0;
sTime.Seconds = 0x0;
sTime.DayLightSaving = RTC_DAYLIGHTSAVING_NONE;
sTime.StoreOperation = RTC_STOREOPERATION_RESET;
if (HAL_RTC_SetTime(&hrtc, &sTime, RTC_FORMAT_BCD) != HAL_OK)
{
Error_Handler();
}
sDate.WeekDay = RTC_WEEKDAY_MONDAY;
sDate.Month = RTC_MONTH_JANUARY;
sDate.Date = 0x1;
sDate.Year = 0x0;
if (HAL_RTC_SetDate(&hrtc, &sDate, RTC_FORMAT_BCD) != HAL_OK)
{
Error_Handler();
}
#endif
/* USER CODE BEGIN RTC_Init 2 */
/* USER CODE END RTC_Init 2 */
}

Answer 3

Here is my startup code for an STM32H7B3LIHxQ processor:
int main(void)
{
/* USER CODE BEGIN 1 */
/* USER CODE END 1 */
/* MPU Configuration--------------------------------------------------------*/
MPU_Config();
/* Enable I-Cache---------------------------------------------------------*/
SCB_EnableICache();
/* Enable D-Cache---------------------------------------------------------*/
SCB_EnableDCache();
/* MCU Configuration--------------------------------------------------------*/
/* Reset of all peripherals, Initializes the Flash interface and the Systick. */
HAL_Init();
/* Configure the system clock */
SystemClock_Config();
/* USER CODE BEGIN SysInit */
#if BACKEND_PERIPERHALS == 1
#if (TRAP_DIV_BY_ZERO_HARD_FAULT == 1 && DEBUG_NMI_FAULTS == 1)
SCB->CCR |= 0x10; // enable div-by-0 trap
#endif
/* Enable the Backup System and VBat parameters */
__HAL_RCC_BKPRAM_CLK_ENABLE();
HAL_PWREx_DisableBatteryCharging();
HAL_PWREx_EnableBkUpReg();
HAL_PWR_EnableBkUpAccess();
/* Enable Back up SRAM */
/* Enable write access to Backup domain */
PWR->CR1 |= PWR_CR1_DBP;
while((PWR->CR1 & PWR_CR1_DBP) == RESET)
{
}
#endif
/* USER CODE END SysInit */
/* Initialize all configured peripherals */
MX_CRC_Init();
MX_GPIO_Init();
MX_DMA2D_Init();
MX_LTDC_Init();
MX_I2C4_Init();
MX_OCTOSPI1_Init();
MX_TouchGFX_Init();
/* USER CODE BEGIN 2 */
#if BACKEND_PERIPERHALS == 1
MX_DMA_Init();
MX_TIM5_Init();
#if ADC2_ENABLED == 1
MX_ADC2_Init();
MX_TIM3_Init();
#endif
MX_CRC_Init();
MX_I2C1_Init();
#if OP_AMPS_ENABLED == 1
MX_OPAMP1_Init();
MX_OPAMP2_Init();
#endif
MX_RNG_Init();
MX_RTC_Init();
...
/**
* #brief System Clock Configuration
* #retval None
*/
void SystemClock_Config(void)
{
RCC_OscInitTypeDef RCC_OscInitStruct = {0};
RCC_ClkInitTypeDef RCC_ClkInitStruct = {0};
RCC_PeriphCLKInitTypeDef PeriphClkInitStruct = {0};
/** Supply configuration update enable
*/
HAL_PWREx_ConfigSupply(PWR_DIRECT_SMPS_SUPPLY);
/** Configure the main internal regulator output voltage
*/
__HAL_PWR_VOLTAGESCALING_CONFIG(PWR_REGULATOR_VOLTAGE_SCALE0);
while(!__HAL_PWR_GET_FLAG(PWR_FLAG_VOSRDY)) {}
/** Configure LSE Drive Capability
*/
// __HAL_RCC_BKPRAM_CLK_ENABLE();
//
// HAL_PWREx_DisableBatteryCharging();
// HAL_PWREx_EnableBkUpReg();
// HAL_PWR_EnableBkUpAccess();
//
// __HAL_RCC_LSEDRIVE_CONFIG(RCC_LSEDRIVE_LOW);
/** Macro to configure the PLL clock source
*/
__HAL_RCC_PLL_PLLSOURCE_CONFIG(RCC_PLLSOURCE_HSE);
/** Initializes the RCC Oscillators according to the specified parameters
* in the RCC_OscInitTypeDef structure.
*/
RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_HSI48|RCC_OSCILLATORTYPE_HSI
|RCC_OSCILLATORTYPE_LSI|RCC_OSCILLATORTYPE_HSE
|RCC_OSCILLATORTYPE_LSE;
RCC_OscInitStruct.HSEState = RCC_HSE_ON;
RCC_OscInitStruct.LSEState = RCC_LSE_ON;
RCC_OscInitStruct.HSIState = RCC_HSI_DIV2;
RCC_OscInitStruct.HSICalibrationValue = 0;
RCC_OscInitStruct.LSIState = RCC_LSI_ON;
RCC_OscInitStruct.HSI48State = RCC_HSI48_ON;
RCC_OscInitStruct.PLL.PLLState = RCC_PLL_ON;
RCC_OscInitStruct.PLL.PLLSource = RCC_PLLSOURCE_HSE;
RCC_OscInitStruct.PLL.PLLM = 12;
RCC_OscInitStruct.PLL.PLLN = 280;
RCC_OscInitStruct.PLL.PLLP = 2;
RCC_OscInitStruct.PLL.PLLQ = 2;
RCC_OscInitStruct.PLL.PLLR = 2;
RCC_OscInitStruct.PLL.PLLRGE = RCC_PLL1VCIRANGE_1;
RCC_OscInitStruct.PLL.PLLVCOSEL = RCC_PLL1VCOWIDE;
RCC_OscInitStruct.PLL.PLLFRACN = 0;
if (HAL_RCC_OscConfig(&RCC_OscInitStruct) != HAL_OK)
{
Error_Handler();
}
/** Initializes the CPU, AHB and APB buses clocks
*/
RCC_ClkInitStruct.ClockType = RCC_CLOCKTYPE_HCLK|RCC_CLOCKTYPE_SYSCLK
|RCC_CLOCKTYPE_PCLK1|RCC_CLOCKTYPE_PCLK2
|RCC_CLOCKTYPE_D3PCLK1|RCC_CLOCKTYPE_D1PCLK1;
RCC_ClkInitStruct.SYSCLKSource = RCC_SYSCLKSOURCE_PLLCLK;
RCC_ClkInitStruct.SYSCLKDivider = RCC_SYSCLK_DIV1;
RCC_ClkInitStruct.AHBCLKDivider = RCC_HCLK_DIV2;
RCC_ClkInitStruct.APB3CLKDivider = RCC_APB3_DIV1;
RCC_ClkInitStruct.APB1CLKDivider = RCC_APB1_DIV1;
RCC_ClkInitStruct.APB2CLKDivider = RCC_APB2_DIV1;
RCC_ClkInitStruct.APB4CLKDivider = RCC_APB4_DIV1;
if (HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_3) != HAL_OK)
{
Error_Handler();
}
PeriphClkInitStruct.PeriphClockSelection = RCC_PERIPHCLK_RTC|RCC_PERIPHCLK_LTDC
|RCC_PERIPHCLK_RNG|RCC_PERIPHCLK_ADC
|RCC_PERIPHCLK_I2C1|RCC_PERIPHCLK_I2C4
|RCC_PERIPHCLK_OSPI;
PeriphClkInitStruct.PLL2.PLL2M = 24;
PeriphClkInitStruct.PLL2.PLL2N = 266;
PeriphClkInitStruct.PLL2.PLL2P = 2;
PeriphClkInitStruct.PLL2.PLL2Q = 2;
PeriphClkInitStruct.PLL2.PLL2R = 2;
PeriphClkInitStruct.PLL2.PLL2RGE = RCC_PLL2VCIRANGE_0;
PeriphClkInitStruct.PLL2.PLL2VCOSEL = RCC_PLL2VCOMEDIUM;
PeriphClkInitStruct.PLL2.PLL2FRACN = 0;
PeriphClkInitStruct.PLL3.PLL3M = 24;
PeriphClkInitStruct.PLL3.PLL3N = 201;
PeriphClkInitStruct.PLL3.PLL3P = 2;
PeriphClkInitStruct.PLL3.PLL3Q = 2;
PeriphClkInitStruct.PLL3.PLL3R = 41;
PeriphClkInitStruct.PLL3.PLL3RGE = RCC_PLL3VCIRANGE_0;
PeriphClkInitStruct.PLL3.PLL3VCOSEL = RCC_PLL3VCOMEDIUM;
PeriphClkInitStruct.PLL3.PLL3FRACN = 5462;
PeriphClkInitStruct.OspiClockSelection = RCC_OSPICLKSOURCE_PLL2;
PeriphClkInitStruct.RngClockSelection = RCC_RNGCLKSOURCE_HSI48;
PeriphClkInitStruct.I2c123ClockSelection = RCC_I2C123CLKSOURCE_D2PCLK1;
PeriphClkInitStruct.I2c4ClockSelection = RCC_I2C4CLKSOURCE_D3PCLK1;
PeriphClkInitStruct.AdcClockSelection = RCC_ADCCLKSOURCE_PLL2;
PeriphClkInitStruct.RTCClockSelection = RCC_RTCCLKSOURCE_LSE;
if (HAL_RCCEx_PeriphCLKConfig(&PeriphClkInitStruct) != HAL_OK)
{
Error_Handler();
}
HAL_RCC_MCOConfig(RCC_MCO1, RCC_MCO1SOURCE_HSI, RCC_MCODIV_1);
}
This code works fine. Ican remove the main supply and the clock and backup ram keep ticking away.

Answer 4

Just gone through your code I was also having similar problem.
In your code here is the problem.
sAlarm.AlarmTime.StoreOperation = RTC_STOREOPERATION_RESET;
It should be following
sAlarm.AlarmTime.StoreOperation = RTC_STOREOPERATION_SET;
In Ioc file go in RTC and change store operation setting to set.
Then uncomment the MX_RTC_Init function.