Syncing of RTC with NTP / Unix time

Projects Programming
1

I am developing an application to start a motor two times a day for filling pellets to my pellet bunker.
The internet is sometimes flaky and might be off for a few days.
Due to remote location there are regular power outings.

That is the reason that I have a Real Time Clock as central time keeper.

Hence the procedure is:

  • Obtain time from NTP server once in 24 hours.
  • Synchronize the RTC (DS3231) with NTP time when internet works.
  • Synchronize the ESP8266 with the RTC

I have no issues except one:
Despite scouring the internet for hours I have not found a way to update the RTC with Unix time.
I use RTClib.h and the obvious NTP code.
The NTP code gives me a time_t object as Unix time (starting seconds from 1970) say
time_t unixTime
One way seems to be to breakdown 'time_t unixTime' to year - month - etc and to synchronize the RTC with the following format asin RTClib:
rtc.adjust(DateTime(YYYY,mm,dd,hh,mm,ss)
However in the technical docs of RTClib (RTClib: DateTime Class Reference) there is a DateTime constructor:
DateTime::DateTime (uint32_t t = SECONDS_FROM_1970_TO_2000)
(btw the notation is above my level of knowledge)
Would this mean that I could use:
rtc.adjust(DateTime(unixTime))

In a test sketch it seems to work however I am not sure because of other use of EEPROM in the sketch.
I am not copying the complete code now it is quite long and mainly boilerplate hence not adding something to the question I think.

Hope someone can help me. Much appreciated.

2

I have an example for ESP8266 NTP and RTC, may be it is of any help:

NTP DST and a RTC for the ESP8266 (rothschopf.net)

3

@noiasca

rtc.adjust(DateTime(tm.tm_year + 1900, tm.tm_mon + 1, tm.tm_mday, tm.tm_hour, tm.tm_min, tm.tm_sec));

With the code you use a struct and update the RTC with yyyy,mm,dd etc
I am looking if the direct use of unix time with DateTime can be done and if it has strange consequences for storage of data in EEPROM or something similar.

4

so just do it,

time_t now; // this are the seconds since Epoch (1970) - seconds GMT
time(&now); // read the current time and store to now

... now is current time now. Use that to adjust your RTC.

5

I have done it now as follows:

time_t F_getNTP() { ...................... }
This function provides NTP time as Unix time (from 1970)

Update the RTC with:

rtc.update(DateTime(F_getNTP());

The RTC is updated correctly. Still don't know of by-effects on EEPROM or so.

Would there be any?

6

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