Hello Dan, On 4/1/25 19:38, Dan Drown wrote: > On 4/1/2025 8:08 AM, Ahmad Fatoum wrote: > : >> We have measured the accuracy we get out of our RTC as mentioned before >> and it's sufficient for our use case. Epson sells this RTC as "High- >> Stability", >> so I do not refuse the claim that cheaper RTCs can be much worse. > : >> This is a wrong summary of my proposal. The RTC is only used as reference >> clock while the system has no network connectivity. Once online, >> system time >> is synchronized against NTP and the RTC is reset to UTC to be better >> equipped >> for the next offline period. > : > > Does your RTC output a PPS and is that PPS connected to a CPU GPIO? If > so, you can use the "local" option to the PPS refclock: > https://chrony-project.org/doc/4.6.1/chrony.conf.html#refclock
Yes, the RTC interrupt is connected to a CPU GPIO. > Chrony can use that to correct the system's frequency and improve the > timekeeping while offline. I have some more details on: https:// > blog.dan.drown.org/strat-2-tcxo/ Thank you. This was insightful. I prefer not to go the PPS route though, but use local as you do for the RTC reference clock instead. That way the kernel driver can be used as-is to set up the periodic interrupt. Thanks, Ahmad -- Pengutronix e.K. | | Steuerwalder Str. 21 | http://www.pengutronix.de/ | 31137 Hildesheim, Germany | Phone: +49-5121-206917-0 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 | -- To unsubscribe email chrony-dev-requ...@chrony.tuxfamily.org with "unsubscribe" in the subject. For help email chrony-dev-requ...@chrony.tuxfamily.org with "help" in the subject. Trouble? Email listmas...@chrony.tuxfamily.org.
