Re: [chrony-users] Setting up Chrony with PPS

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On 18/02/2016 22:48, Deven Hickingbotham wrote:

$cat /sys/class/pps/pps0/assert

Are you seeing those?

Yes, but just one timestamp per execution:

pi@gps ~ $ cat /sys/class/pps/pps0/assert
pi@gps ~ $ cat /sys/class/pps/pps0/assert
pi@gps ~ $ cat /sys/class/pps/pps0/assert
pi@gps ~ $ cat /sys/class/pps/pps0/assert

Okay so your PPS looks fine.

I think what's happening (and I'm half guessing but I did the following in the past to solve the same problem) is that you have two separate refclocks. One is your GPS NMEA (which is working), and the other is your PPS source ... which is only providing timing, not time.

I believe you need to make it so that the PPS refclock is treated as a sort of extension of the GPS refclock, then prevent the GPS refclock from being selected on its own:

refclock SHM 0 refid GPS precision 1e-1 offset 0.9999 delay 0.2 noselect
refclock SOCK /var/run/chrony.ttyAMA0.sock refid PPS lock GPS

I'm not sure why you see "PP" in the "chronyc sources" output - double-check your file on disk for dodgy line endings perhaps? Bit of a concern if the trailing "S" now gets truncated in my example above.

Anyway, give that a try.


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