On 2011-01-14, David J Taylor <david-tay...@blueyonder.co.uk.invalid> wrote: > Folks, > > You may recall that I had a problem with a Garmin GPS18x LVC after > firmware upgrades, where the offset between the leading edge of the PPS > signal and the end of the NMEA serial data exceeded one second. With some > help from Hal Murray who knows more of NTP than I do, we have worked round > the problem as described here: > > http://www.satsignal.eu/ntp/FreeBSD-GPS-PPS.htm#gps-18x > > The basic steps were: > > - make the GPX18x LVC "noselect" so that NTP would not use it > > - enable the peerstats to measure where NTP thought the 18x end of message > occurred > > - analyse the peerstats file to determine the apparent offset (which > was -1.000 seconds, as it happened) > > - add that offset (as +1.000 seconds) to the fudge time2 value for the 18x > in the ntp.conf > > - restart NTP > > I hope that helps someone.
This is a problem in the coding of the program (gpsd?) that you are using to get the data. The computer clock is a good device for measuring the time between the PPS. The timestamp on the PPS and the timestamp on the beginning and end of the nmea transmission are more than sufficient infomation to link the nmea time to the PPS. While I agee that the GPS should not be taking more an a second to get the time to you, the program should also be robust enough to take that into account. > > Cheers, > David > _______________________________________________ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
