Many ways to skin a cat! I use the RTC and it's 1Hz output for normal operation. And then at 3am I use a GPS (which actually is an ESP-01) to connect NTP and send a fake GPS message which then syncs the RTC.
The only niggle is DST on the RTC and the GPS sides... I operate with a DST rule and the RTC so the clock would continue to run correctly even if a zombie apocalypse took out the NTP infrastructure. (I actually have a RPi on my local network which amongst other things provides NTP to the local network) Regards G On Wed, 29 Sep 2021, 19:44 Paul Andrews, <p...@nixies.us> wrote: > I use NTP. I pull time from the RTC until I get a a sync from the internet > - then I switch to the internet and I update the RTC whenever I get an > update from the network. It all uses UTC, which is converted to local time > for display. > > On Wednesday, September 29, 2021 at 2:01:32 PM UTC-4 gregebert wrote: > >> I'm using network time that my Raspberry Pi re-acquires roughly every 20 >> minutes, with a DS3232 for backup when the internet is down. I need to >> tweak the software a bit more to automatically update the DS3232; right now >> I have to use my debug utility to manually update it. But this does allow >> me to see how much long-term drift there is. Here is an actual check from >> today: >> >> INIT: RTC module = 09/29/21 08:52:56 >> INFO: NTP sync acquired at 09/29/21 09:52:12 >> >> It's been about 6 months since I sync'd the time, and this particular >> DS3232 RTC has gained 44 seconds. That's about 3PPM, which is pretty close >> to the datasheet spec of 2PPM. I have not made any attempt to use the trim >> register yet, but now that I have this data I might give that a shot. >> >> >> >> >> On Wednesday, September 29, 2021 at 9:34:27 AM UTC-7 nixiebunny wrote: >> >>> My latest scope clock uses a DS3232 RTC chip for general timekeeping. >>> This chip only keeps time to the nearest second, as far as the >>> user-readable registers are concerned. >>> I also have a USB port that can read the time from a GlobalSat GPS puck. >>> This reports the time once a second through the Arduino TinyGPS library, >>> with the age of the time in milliseconds (typically 250). This should let >>> me compensate for the read delay by setting the tick (50/60Hz) counter in >>> my local time variables. >>> What do any of you time nuts do about displaying the time accurately, >>> and making the RTC be reasonably accurate compared to the GPS? >>> Do you discipline the RTC with GPS? Do you just ignore the RTC when GPS >>> is available? Set the RTC occasionally? >>> >>> -- > You received this message because you are subscribed to the Google Groups > "neonixie-l" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to neonixie-l+unsubscr...@googlegroups.com. > To view this discussion on the web, visit > https://groups.google.com/d/msgid/neonixie-l/75498a13-76c8-4c08-b7a6-c66e923443dan%40googlegroups.com > <https://groups.google.com/d/msgid/neonixie-l/75498a13-76c8-4c08-b7a6-c66e923443dan%40googlegroups.com?utm_medium=email&utm_source=footer> > . > -- You received this message because you are subscribed to the Google Groups "neonixie-l" group. To unsubscribe from this group and stop receiving emails from it, send an email to neonixie-l+unsubscr...@googlegroups.com. To view this discussion on the web, visit https://groups.google.com/d/msgid/neonixie-l/CAD-YxBXO3-ugOV0b5sBF9j7VjRxoAvxQNjFpBOtT2tydwhP%3DTA%40mail.gmail.com.
