[ntp:questions] PPS signal from Garmin GPS 18x LVC

David Lord snews at lordynet.org
Sun Dec 29 21:40:19 UTC 2013


Adrian P wrote:
> Thank you very much David!
> 
> So "o" means PPS is used... In my case, I only have "*" in front of
> the driver IP.... So I suppose NTP is not using the PPS signal... hmm,
> wondering why. This is my output:
> 
> server 127.127.20.0 mode 1 minpoll 4 maxpoll 4 prefer
> fudge 127.127.20.0 flag1 1 flag2 0 flag3 1 refid PPS
> 
> root at debian:~# ntpq -crv -pn
> associd=0 status=0415 leap_none, sync_uhf_radio, 1 event, clock_sync,
> version="ntpd 4.2.6p5 at 1.2349-o Sat May 12 09:07:18 UTC 2012 (1)",
> processor="i686", system="Linux/3.2.0-4-686-pae", leap=00, stratum=1,
> precision=-19, rootdelay=0.000, rootdisp=39.519, refid=PPS,
> reftime=d66ab9bb.59e07233  Sun, Dec 29 2013 17:09:47.351,
> clock=d66ab9ca.45e6469f  Sun, Dec 29 2013 17:10:02.273, peer=52263, tc=4,
> mintc=3, offset=14.437, frequency=50.557, sys_jitter=23.063,
> clk_jitter=19.669, clk_wander=5.553
>      remote           refid      st t when poll reach   delay   offset  jitter
> ==============================================================================
> *127.127.20.0    .PPS.            0 l   15   16  377    0.000   14.437  23.063
> root at debian:~#
> 
> This is a Debian linux that I am using right now , and ppswatch is
> telling me that PPS signal is present:

I'm using NetBSD with ntpd 4.2.7p401 and type 22 driver for
PPS but I found I needed

tos mindist 0.4

to ensure pps was picked up. I probably could get away with a
lower value but my Sure gps type 20 driver is showing offset
of about 20ms rms and 80 ms pk.

ntpq -crv gives sync_pps, refid=PPSb, offset=-0.001413.

When I tried with Ubuntu sometime during 2009 I had to install
the ppskit package but doubt that is needed now.

On my setup, if pps isn't picked up within some short period
it's likely not synced at all. I usually reboot which seems to
always lock to pps within a few minutes, rather than  try
restarting ntpd which sometimes never syncs to pps.


another David



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