[ntp:questions] How to debug GPS PPS?
David J Taylor
david-taylor at blueyonder.delete-this-bit.and-this-part.co.uk.invalid
Fri Feb 12 20:14:10 UTC 2010
"xyz-2041" <xyz2041 at gmail.com> wrote in message
news:1ae0f584-2dd7-4244-8a58-0c31df8067ec at r33g2000yqb.googlegroups.com...
> OK. Couldn't get the Oncore unit to work in any way
> shape or form. I bought a DB9 LED tester like this:
> Had PPS going to pin 1, DATA OUT to pin 2, and DATA IN to pin 3.
> 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
> /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
> to get it to behave?
with an offset of -716ms, NTP is unlikely to sync to it. Any chance that
you are syncing to the wrong edge of the PPS signal, and that you need to
use one of the fudge settings to invert the polarity?
"flag2 0 | 1
If PPS signal processing is enabled, capture the pulse on the rising
edge if 0 (default); capture on the falling edge if 1. "
Just a suggestion.
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