Re: [gpsd-users] gpsd and chrony without 3D Fix

[Miroslav Lichvar]

On Fri, Dec 12, 2014 at 03:18:20PM -0500, Alex Olihovik wrote:
> Is gpsd doing something to tell chrony not to use the GPS or 1PPS data when
> a fix can't be achieved?

When the fix is lost, gpsd will stop sending new samples to
chronyd/ntpd and after few missed samples the source will be marked as
unreachable.

> Is there a way I can force this gpsd/chrony
> interface to work without a 3D fix? Is this a gpsd or chrony issue?

If chronyd is compiled with PPS support, you could configure it to use
the PPS device directly and use the message timing source (SHM 0) from
gpsd. This way, the SHM 0 source will be needed only for the initial
sync. The two sources are independent and PPS can work even when SHM 0
stops.

In chrony.conf that could be:

refclock SHM 0 offset 0.5 delay 0.2 refid NMEA
refclock PPS /dev/pps0

You may need to adjust the offset value for your GPS device so that
the two sources agree with each other and are not rejected as
falsetickers by chronyd. Also, if you don't use the ldattach program
or similar to create the PPS device, chronyd will need to be started
after gpsd.

-- 
Miroslav Lichvar