[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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