[ntp:questions] Have Pi, have GPS = low powered NTP server?

bealevideo at gmail.com bealevideo at gmail.com
Mon Aug 6 22:35:38 UTC 2012


In case of interest, I got NTP with PPS from a GPS receiver running on the Raspberry Pi.  My peak error (looking at the kernel's PPS timestamps) went from about +/- 2 msec using remote NTP servers, to about 60 usec with PPS enabled (limited by variability in the R-Pi's interrupt latency.) Using "Raspbian" kernel compiled with PPS support. More info, and graphs at
http://www.raspberrypi.org/phpBB3/viewtopic.php?f=41&t=1970&start=25#p142606

pi at raspberrypi:~$ /usr/local/bin/ntpq -c peer -c as -c rl

     remote           refid      st t when poll reach   delay   offset  jitter
==============================================================================
*stratum-2-core- 129.7.1.66       2 u   53   64  377   63.748   -1.330   1.625
+four10.gac.edu  18.26.4.105      2 u   29   64  377   59.207    2.768   0.346
+sola-dal-09.ser 64.250.177.145   2 u   36   64  377   48.895    3.617   0.703
+tick.tadatv.com 10.0.22.51       2 u   55   64  377   10.340    2.228   0.148
oPPS(0)          .PPS.            0 l    2   16  377    0.000    0.009   0.012

ind assid status  conf reach auth condition  last_event cnt
===========================================================
  1 46881  963a   yes   yes  none  sys.peer    sys_peer  3
  2 46882  9424   yes   yes  none candidate   reachable  2
  3 46883  9424   yes   yes  none candidate   reachable  2
  4 46884  9424   yes   yes  none candidate   reachable  2
  5 46885  973a   yes   yes  none  pps.peer    sys_peer  3

associd=0 status=011d leap_none, sync_pps, 1 event, kern,
version="ntpd 4.2.6p3 at 1.2290 Mon Aug  6 02:06:19 UTC 2012 (1)",
processor="armv6l", system="Linux/3.1.9-pps+", leap=00, stratum=1,
precision=-19, rootdelay=0.000, rootdisp=0.288, refid=PPS,
reftime=d3ca91b1.315968df  Mon, Aug  6 2012 11:55:45.192,
clock=d3ca91b3.f1638fef  Mon, Aug  6 2012 11:55:47.942, peer=46885, tc=4,
mintc=3, offset=0.009, frequency=-37.252, sys_jitter=0.012,
clk_jitter=0.000, clk_wander=0.003



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