[ntp:questions] How to debug GPS PPS?
David Lord
snews at lordynet.org
Fri Feb 12 21:17:38 UTC 2010
xyz-2041 wrote:
> OK. Couldn't get the Oncore unit to work in any way
> shape or form. I bought a DB9 LED tester like this:
>
> <http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=260546635257>
>
> Had PPS going to pin 1, DATA OUT to pin 2, and DATA IN to pin 3.
> Still
> no good.
>
> Bought a Garmin GPS 25-LVC, put it in an enclosure, commented
> out the Oncore driver and added to ntp.conf:
>
> # Garmin / PPS driver:
> server 127.127.20.0 prefer
> fudge 127.127.20.0 refid GPS
>
> Restarted:
>
> /etc/rc.d/ntpd restart
>
> Checking the status:
>
> # ntpq -c pe
>
> remote refid st t when poll reach delay
> offset jitter
> ==========================================================
> xGPS_NMEA(0) .GPS. 0 l 15 64 377 0.000
> -716.52 105.934
>
>
> Looks like it is being read, but is off by quite a bit. Any ideas on
> how
> to get it to behave?
For my gps18x-LVC I have following config:
tos orphan 10
tos mindist 0.4 # I could reduce this now
server 127.127.20.0 mode 1 prefer
fudge 127.127.20.0 time1 0.651 refid GPSb
server 127.127.22.0 minpoll 4 maxpoll 6
fudge 127.127.22.0 refid PPSb flag3 1
server serv1
server serv2
server serv3
ntpq -p me6000
remote refid poll reach offset jitter
+GPS_NMEA(0) .GPSb. 64 377 -12.625 21.361
oPPS(0) .PPSb. 16 377 0.002 0.002
serv1 64 377 0.039 0.660
serv2 64 377 -0.532 0.513
serv3 64 377 -2.486 0.639
Note the GPS_NMEA is all over place. I only just changed to
above config (looks to be giving lower PPS offset/jitter) and
restarted ntpd but yesterday with almost same config
peer_summary has:
ident cnt mean rms max
127.127.22.0 5238 0.003 0.031 0.066
127.127.20.0 1339 8.017 21.307 92.970
David
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