| Re: [chrony-users] PPS Synchronization Verification |
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On Mon, 2 Nov 2020, Miroslav Lichvar wrote:
On Mon, Nov 02, 2020 at 12:24:32PM +0000, Chang, Benjamin wrote:
The PPS signal is coming from the NTP server (it's a syncserver S650) and is connected via a 232 line. I essentially did this https://www.crc.id.au/2016/09/24/adding-a-pps-source-to-ntpd/ but switched the ntpd kernel with the chrony kernel. Should I set an offset of .00002 for the PPS?
20 microseconds for an interrupt? That seems pretty high. One tests I ran
about 10 years ago, (sending a timed signal over on the parallel port lines to
the serial port interrupt line) the latency was closer to or less than 1 microsecond.
Yes, that should make two sources agree with each other. Or, you can
add the opposite correction to the NTP source. Without a trusted time
source it's difficult to tell which one is more accurate. If you
enabled hardware timestamping, I'd probably trust more the NTP source.
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Miroslav Lichvar
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