Hello ST community!
We're using STM32F401RDT6.
We use the RTC to maintain scheduled events that occur in the time we set, but not with the RTC's Alarm mechanism, rather our custom-made mechanism based on the current epoch time which is being updated every ~4 seconds.
Between each epoch sampling, the MCU goes to sleep.
Here is the rtcEpochGet function we have made:
uint32_t rtcEpochGet()
{
struct tm time_tm;
time_t t_of_day;
uint32_t tmp;
RTC_TimeTypeDef MyTimeStruct;
RTC_DateTypeDef MyDateStruct;
HAL_RTC_GetTime(&hrtc, &MyTimeStruct, RTC_FORMAT_BIN);
HAL_RTC_GetDate(&hrtc, &MyDateStruct, RTC_FORMAT_BIN);
// Read the last epoch time stored in RTC back-up register
tmp = HAL_RTCEx_BKUPRead(&hrtc, RTC_BKP_DR19);
// Check if the last epoch match to 12:59:56 PM (or later)
// If yes - next hour should be 13, not 1 (14 not 2, etc)
// if (tmp % 86400 >= 46796 && hrtc.Init.HourFormat == RTC_HOURFORMAT_24 && MyTimeStruct.Hours <= 12)
// MyTimeStruct.Hours += 12;
// Source: https://www.epochconverter.com/programming/c
time_tm.tm_year = MyDateStruct.Year+2000-1900; // Year-1900
time_tm.tm_mon = MyDateStruct.Month-1; // Month, where 0 = jan
time_tm.tm_mday = MyDateStruct.Date; // Day of the month
time_tm.tm_hour = MyTimeStruct.Hours;
time_tm.tm_min = MyTimeStruct.Minutes;
time_tm.tm_sec = MyTimeStruct.Seconds;
time_tm.tm_isdst = -1; // Is DST on? 1 = yes, 0 = no, -1 = unknown
t_of_day = mktime(&time_tm);
HAL_RTCEx_BKUPWrite(&hrtc, RTC_BKP_DR19, t_of_day);
return t_of_day;
}
In a background-running task we follow the time by using: rtcEpochGet()%(24*3600) which return the current time, in seconds, since midnight.
The issue is that when we are passing 12:59:59 (AM) to 13:00:00 (PM), the HAL function HAL_RTC_GetTime returns 1 instead of 13 to MyTimeStruct.Hours.
As you can see, we are working around this issue by checking if the last epoch time was 12:59:56 or later, and if so, we are adding 12 to the "hours" member. But this is only dealing with the symptom, instead of solving the problem.
RTC driver is set to 24_HOURS_FORMAT, calendar has activated no alarms.
I hope someone here could help us solve this issue.
Thanks,
Raz.
