I am using an STM32H743 user board with STMCubeIDE. I want to use the internal RTC calendar with the internal clock (LSI). Q: first power on clock start 17:20:00 then time is going. For example, when time is 17:20:50 suddenly I power off the

[Abdelmalek BELLOULA]

MX_RTC_Init();

if (HAL_RTCEx_BKUPRead(&hrtc, RTC_BKP_DRX) != 0X2233) {

printf(" Set Date and Time \r\n");

SetDateTime();

}

void SetDateTime(void) {

RTC_TimeTypeDef sTime = { 0 };

RTC_DateTypeDef sDate = { 0 };

/* USER CODE BEGIN Check_RTC_BKUP */

/* USER CODE END Check_RTC_BKUP */

/** Initialize RTC and set the Time and Date*/

sTime.Hours = 0x19;

sTime.Minutes = 0x45;

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();

}

sDate.WeekDay = RTC_WEEKDAY_FRIDAY;

sDate.Month = RTC_MONTH_MARCH;

sDate.Date = 0x25;

sDate.Year = 0x22;

if (HAL_RTC_SetDate(&hrtc, &sDate, RTC_FORMAT_BCD) != HAL_OK) {

Error_Handler();

}

HAL_RTCEx_BKUPWrite(&hrtc, RTC_BKP_DRX, RTC_BKP_DATA);

}

[waclawek.jan]

There is no question, but I'll try to guess: LSI is not in battery-backup domain, so it stops working when VDD is removed.

LSI is also very imprecise, see datasheet.

JW

[Abdelmalek BELLOULA]

Thank you for the answer indeed I have a problem with the time display, it freezes as soon as I remove the power supply.

I started to test with LSE I have the same problem and also the fact that the display of seconds is not very stable (periodic)

[waclawek.jan · Accepted solution]

Then your LSE oscillator is probably not stable.

Read AN2867. Try on a "known good" board like Nucleo or Disco. Experiment with LSE drive level.

JW

[Abdelmalek BELLOULA]

Thanks for your help

[Abdelmalek BELLOULA]

The problem is solved, it works very well, the problem comes from a fault in the oscillator at the level of the PC14-OSC32_IN and PC15-OSC32_OUT pins.

Thank you waclawek.jan for your orientation