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

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On Thu, 18 Feb 2016, Deven Hickingbotham wrote:

First off, thanks for all of the responses! I'm testing your suggestions as fast as I can and if I apologize if I don't directly reply to a suggestion.

Does /var/run/chrony.ttyAMA0.sock exist? If not, then it is hard to read
it. Your gpsd does not seem to be writing to SHM0

Yes, it does exist:

pi@gps /var/run $ ls -l *.sock
srwxr-xr-x 1 root root 0 Feb 18 16:23 chrony.ttyAMA0.sock
srw-rw---- 1 root root 0 Feb 18 15:43 dhcpcd.sock
srw-rw-rw- 1 root root 0 Feb 18 15:43 dhcpcd.unpriv.sock
srwxr-xr-x 1 root root 0 Feb 18 16:23 gpsd.sock

OK, not sure what it does

But I don't think it existed before I configured chrony.

I suspect it is a socket that chrony listens to, but there needs to be
something that actually writes to that socket as well. But I have never used sockets on chrony so have no idea.

I am also concerned that your outside clocks are way off ( hundreds of ms )
and have HUGE variances -- the network, unless you are using smoke
signals for
your network, should not be out by a hundred ms. Mind you telling your
that  your SHM0  is out by 135ms is probably all wrong, and is part of the

So, I would first suggest that you get rid of the nmea, and just use the
external clocks as your reference. and get PPS working. Then  you can
try to
get nmea working.  One thing at a time.

After removing the refclock references from chrony.conf I get:

pi@gps ~/SystemFiles $ chronyc sources
210 Number of sources = 4
MS Name/IP address     Stratum Poll LastRx Last sample
^+     3    7     43    +16ms[  +14ms] +/-   89ms
^? mirror                  3    7     41    +17ms[  +17ms] +/-  134ms
^~   16    6     59    +71ms[  +55ms] +/-   55ms
^*          1    6     59    +15ms[ -696us] +/-  122ms

Is this more in line with what you expected?

Nope. Those are huge uncertainties for network timing. 134ms uncertainty
corresponds to light travel time around the earth uncertainty. I would expect
more like +- 100 microseconds, not milliseconds.

What is your network link?

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