On 2013-08-28, David Taylor <david-tay...@blueyonder.co.uk.invalid> wrote: > On 28/08/2013 10:10, Rob wrote: >> detha <de...@foad.co.za> wrote: >>> I have a test setup with a RaspberryPi and a SiRF/gpsd module. All >>> working quite well, but one thing bugs me. Looking at the ntpq -p output >>> the serial port readings seem to drift away slowly but steadily from the >>> PPS, see <http://detha.co.za/ntp/ntpmon.20130828.jpg>. >> >> It is normal. The offset between serial data and PPS changes all the time. >> >> It is often a bit better when you put the GPS in binary mode instead >> of NMEA. > > Indeed, or use a very high baud rate for the NMEA. > > I would be more worried about the 11 ms step in the PPS at about -155 > hours....
If you look closely that is an 11ms step in the external stratum 1 servers, not in PPS. The lgiht blue line goes straight through at 0 at that time. (hard to see since the background is almost the same shade of grey) > > Nice graph, though.... _______________________________________________ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions