"Harlan Stenn" <[EMAIL PROTECTED]> wrote in message news:[EMAIL PROTECTED] > The time reported by your NMEA clock is far enough away from your other 2 > sources that ntpd is not believing your NMEA clock. > > H
Hi, it's supposed to be working with PPS; that is the absolute time reference. I'm using a Garmin GPS25 as per the example in the NMEA Refclock documentation. It has only the $GPRMC output string turned on, at once per second. Others are using successfully using exactly the same hardware - e.g. from Dave Morgan in reply to my previous topic: "I am running a gps25hlv direct with no extra conversion for the PPS but with a 2.4.29-NANO kernel on a Debian/Woody system." The NMEA data is only 4800 Baud, sent after the PPS edge that it relates to - by the time the NMEA string has been received and validated, it's got to be waaay behind the 'real time' reference pulse edge. In practice, looking at the serial lines with my vintage 'Interfaker' RS232 monitor box, the GPS does not send the serial data until visibly well after the END of the 200mS PPS pulse. This is the basis of any serial + PPS GPS, so presumably this is what the refclock driver expects. The real problem seems to be that the PPS signal is not being seen somewhere along the way, or is somehow too unstable (in terms of kernel timing) to be processed.. Robert Jenkins. _______________________________________________ questions mailing list [email protected] https://lists.ntp.isc.org/mailman/listinfo/questions
