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How to resolve the STM3F407VG RTC accuracy problems?
Do we able to calibrate the RTC for better accuracy?
Peter BENSCHBest answer
ST Technical Moderator
August 17, 2021
Calibration can be done by just a call to HAL_RTCEx_SetSmoothCalib, which is part of stm32f4xx_hal_rtc_ex.c or by setting the required parameter manually. You have certainly read the above-mentioned section 26.3.11 carefully so that you will immediately understand how the following, very simple function works, which incidentally is independent of the target and does not yet contain a check for the range of parameters. Simply call it anywhere in your user program to set the correction value to -511 ... +512 steps:
/**
* @brief Sets the new correction values for smooth calibration into RTC_CALR, fixed for calibration period of 32s
* @param calibration value -511...+512 for calculating CALP, CALM[8..0]
* @retval none
*/
void wr_LSEcalibration(int16_t LSEcalibrationvalue)
{
if (LSEcalibrationvalue > 0)
{
if (HAL_RTCEx_SetSmoothCalib(&hrtc, RTC_SMOOTHCALIB_PERIOD_32SEC, RTC_SMOOTHCALIB_PLUSPULSES_SET, (uint32_t)(512-LSEcalibrationvalue)) != HAL_OK)
{
Error_Handler();
}
}
else
{
if (HAL_RTCEx_SetSmoothCalib(&hrtc, RTC_SMOOTHCALIB_PERIOD_32SEC, RTC_SMOOTHCALIB_PLUSPULSES_RESET, (uint32_t)abs(LSEcalibrationvalue)) != HAL_OK)
{
Error_Handler();
}
}
}Regards
/Peter
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