[ntp:questions] why does ntp refuse my pps source

folkert folkert at vanheusden.com
Sun Jul 14 18:40:25 UTC 2013


Hi,

I have a raspberry pi with a adafruit gps module.
This RPI runs linux with a kernel adapted for PPS.

This is time4:
     remote           refid      st t when poll reach   delay   offset  jitter
==============================================================================
*time1.intranet. .PPS.            1 u  475 1024  377    0.539    0.336   0.282
+time3.intranet. .PPS.            1 u 1014 1024  377    0.961    0.198   0.195
+time2.intranet. 192.168.64.2     2 u  452 1024  377    1.726    0.037   0.198
-auth1.xs4all.nl 134.221.205.12   2 u  779 1024  377   18.207   -2.128   0.191
xSHM(0)          .NMEA.           0 l    9   16  377    0.000  -348.89  12.214
xPPS(0)          .PPS.            0 l   10   16  377    0.000    0.354   0.002

ind assid status  conf reach auth condition  last_event cnt
===========================================================
  1 29160  961a   yes   yes  none  sys.peer    sys_peer  1
  2 29161  941a   yes   yes  none candidate    sys_peer  1
  3 29162  9414   yes   yes  none candidate   reachable  1
  4 29163  9314   yes   yes  none   outlyer   reachable  1
  5 29164  911a   yes   yes  none falsetick    sys_peer  1
  6 29165  9114   yes   yes  none falsetick   reachable  1

associd=29165 status=9114 conf, reach, sel_falsetick, 1 event, reachable,
srcadr=PPS(0), srcport=123, dstadr=127.0.0.1, dstport=123, leap=00,
stratum=0, precision=-20, rootdelay=0.000, rootdisp=0.000, refid=PPS,
reftime=d58d6c66.ffe7320f  Sun, Jul 14 2013 20:28:54.999,
rec=d58d6c67.8bdeabe2  Sun, Jul 14 2013 20:28:55.546, reach=377,
unreach=0, hmode=3, pmode=4, hpoll=4, ppoll=4, headway=0, flash=00 ok,
keyid=0, offset=0.378, delay=0.000, dispersion=0.233, jitter=0.010,
filtdelay=     0.00    0.00    0.00    0.00    0.00    0.00    0.00    0.00,
filtoffset=    0.38    0.38    0.38    0.37    0.37    0.36    0.36    0.36,
filtdisp=      0.00    0.24    0.48    0.72    0.96    1.20    1.44    1.68

I find this rather strange.

Time1 is a regular pc with a garmin 18x lvc, time3 is an rpi with pps.
Time2 is also an rpi with a adafruit gps with pps but using a userspace
pps implementation instead (which might explain why it chooses a remote
time source over its local pps).

Any ideas?


Folkert van Heusden

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