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On Mon, 11 Sep 2017, Miroslav Lichvar wrote:

On Mon, Sep 11, 2017 at 03:01:13AM +0000, Simon Haines wrote:
The GPS is connected through gpsd using the SHM driver, and I've confirmed
it is working (refclock log is below). Here is my chrony.conf:
# cat /etc/chrony.conf
refclock PPS /dev/pps0 lock NMEA
refclock SHM 0 offset 0.5 delay 0.2 refid NMEA noselect

Try changing the offset to 0.1. From the log below it looks like the
offset between the two refclocks is too large and prevents their
locking.

shm 0 is noselect so it should not matter. Also PPS is the pluse which is the
clock's own time (in seconds) beeing fed back to it. (Ie, the nanoseconds are
correct UTC but the seconds are whatever the system clock says they are), so
it should not prevent a lock.



1970-01-01T01:03:34Z refclock.c:465:(RCL_AddPulse) refclock pulse ignored
offdiff=0.380447388 refdisp=0.000001260 disp=0.000000001
1970-01-01T01:03:34Z refclock.c:723:(filter_add_sample) filter sample 2
t=3814.536533857 offset=1505092242.963466167 dispersion=0.000001000
1970-01-01T01:03:35Z refclock.c:465:(RCL_AddPulse) refclock pulse ignored
offdiff=0.381711483 refdisp=0.000001260 disp=0.000000001

Further help with synchronising to the PPS would be appreciated, as would
any configuration advice for an isolated system with a large time delta at
boot (I am considering 'makestep 0.1 300' assuming 5 minutes for the GPS to

Please note that the second argument of makestep is number of updates
and not seconds.

--
Miroslav Lichvar

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