[time-nuts] gpsd and ntp

Tim Cwik timenuts at stnhbr.com
Mon Oct 26 20:29:26 UTC 2009


Cross posted, hopefully not inappropriately.

I am using gpsd with a Trimble Thunderbolt to supply time and PPS to 
ntpd for a time server.
The Tbolt shows serial output, PPS signal looks ok, and is detected by gpsd.

ntpq -p shows:

# ntpq -p
      remote           refid      st t when poll reach   delay   offset  
jitter
==============================================================================
+nonce.prolixium 209.51.161.238   2 u   24   64  377   46.131   26.478  
59.117
  u15161952.onlin 209.51.161.238   2 u  12h 1024    0  218.935  
-38.878   0.000
  skywiley.com    131.107.13.100   2 u  33d 1024    0   88.930    
2.426   0.000
+redline.mednor. 209.81.9.7       2 u    7   64  377   92.425   21.976  
64.496
  octopus.stnhbr. .STEP.          16 u    - 1024    0    0.000    
0.000   0.000
  SHM(0)          .GPS.            0 l   5h   16    0    0.000  
-641.16   0.001
*SHM(1)          .GPS1.           0 l    4   16  377    0.000    0.024   
0.060
  LOCAL(0)        .LOCL.          10 l    2   64  377    0.000    
0.000   0.001

I never see ntpd use the SHM(0) output from gpsd. The shared memory is 
ok, I think, because it does see the PPS time in SHM(1).

My ntp.conf includes:

server 127.127.28.0 minpoll 4 maxpoll 4
fudge 127.127.28.0 refid GPS

server 127.127.28.1 minpoll 4 maxpoll 4 prefer
fudge 127.127.28.1 refid GPS1

I assume I want to be using the GPS time from the serial port through 
SHM(0) and that this should be one of the peers and would make my 
solution more independent of external time servers should my network 
connection fail.

Thanks for any advice.

Tim
N2LTQ



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