| Re: [chrony-dev] [RFC] Transparent fallback from NTP reference clock to RTC |
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- To: chrony-dev@xxxxxxxxxxxxxxxxxxxx
- Subject: Re: [chrony-dev] [RFC] Transparent fallback from NTP reference clock to RTC
- From: Dan Drown <dan-ntp@xxxxxxxxx>
- Date: Tue, 1 Apr 2025 12:38:02 -0500
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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
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/
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