Some of the DS chips have a square wave input that can be fed from a GPS PPS and the RTC will discipline itself. It can also produce a PPS when the GPS stops.
The question is, is NTP's holdover on the system clock better than NTP disciplining the system clock with an RTC PPS. I'd guess not. Forget about accurate time from the RTC's registers. The slowness and variably in I2C is quite poor and most of them don't even have sub-second resolution when read or written. On Nov 1, 2017 4:22 PM, "MLewis" <mlewis...@rogers.com> wrote: Is this a workable or worthwhile strategy?: - RTC providing date & time to second to system on boot - RTC frequency output driving a counter/divider to produce PPS - GPS module providing UTC PPS - GPS module's secondary PPS disciplining the RTC-counter-divider PPS by resetting the RTC's counter/divider (I'm assuming there's one that will rest fast enough to sync; I've never looked into these...) If GPS PPS is lost, then the RTC counter/divider is producing a recently disciplined PPS. Valid or invalid? And the DS3231 has: - a 32K output, and - an Active-Low-Interrupt/SQW output that can be set to PPS. It's unclear to me how to sync the DS3231 PPS to the GPS PPS, or if that can be done. Thanks, Michael _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/m ailman/listinfo/time-nuts and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.