Hi All,
I've got a SiRF star 3 GPS with a PPS line which im trying to get
running on a machine with ubuntu 12.10 and a serial port using the DCD
line for pps signalling. Took quite a while as the ntpd that ships with
ubuntu 12.10 appears to be compiled without pps support (please correct
me if im wrong here - but no matter what I do, the shipped version never
tries to open /dev/pps0, gpspps0, etc etc and i've checked permissions
and apparmor) - also theres alot of contradictory info on the net about
how you get pps and gps operating this way (took some time to find that
i needed "flag1 1" in the gps settings - which alot of articles dont
mention).
But, once it was up and running it appeared to work very well, after a
few hours the jitter was down to below 0.01. Next I added in a few
external time sources, and i ended up with this:
remote refid st t when poll reach delay offset
jitter
==============================================================================
203.0.178.191 216.218.254.202 2 u 14 64 3 8.704 990.003
0.189 (my isp)
203.82.209.217 18.26.4.105 2 u 18 64 3 62.372 997.624
0.466 (pool server)
202.127.210.36 223.255.185.2 2 u 19 64 3 22.454 1067.75
1.747 (pool server)
130.102.2.123 130.102.132.164 2 u 17 64 3 22.947 1000.23
0.392 (pool server)
202.125.45.77 223.252.32.9 2 u 17 64 3 24.810 1001.95
0.849 (pool server)
*127.127.20.0 .GPS. 0 l 7 8 377 0.000 0.467
0.209 (GPS)
Everythings almost exactly 1 second out. Reading around about this, it
appears that this occurs cause theres possibly too many sentences coming
across the 4800 baud serial line, is that correct?
After adjusting "fudge time2", i ended up with with this:
remote refid st t when poll reach delay offset
jitter
==============================================================================
-203.0.178.191 216.218.254.202 2 u 51 64 377 9.070 -5.518 1.423
-202.127.210.36 223.255.185.2 2 u 53 64 377 21.729 74.408 4.701
*203.192.179.99 223.252.32.9 2 u 48 64 377 22.956 17.581 3.551
+119.148.67.183 203.12.160.2 3 u 51 64 377 21.200 4.094 1.439
+203.192.179.98 203.35.83.242 2 u 50 64 377 22.735 17.913 27.315
o127.127.20.0 .GPS. 0 l 3 8 377 0.000 5.080 0.193
and a few hours later:
remote refid st t when poll reach delay offset
jitter
==============================================================================
+203.0.178.191 216.218.254.202 2 u 44 64 377 9.041 -10.309
0.356
+202.127.210.36 223.255.185.2 2 u 50 64 377 21.547 64.812 6.039
+203.192.179.99 210.9.192.50 2 u 35 64 377 23.000 -0.256 2.525
-119.148.67.183 203.12.160.2 3 u 48 64 377 21.006 -15.580
4.364
-203.192.179.98 203.35.83.242 2 u 49 64 377 23.130 74.392 26.231
o127.127.20.0 .GPS. 0 l 4 8 377 0.000 -0.065 0.003
and the config i've ended up with is:
server 127.127.20.0 mode 1 minpoll 2 maxpoll 4 prefer
fudge 127.127.20.0 flag1 1 flag2 0 flag3 1 time2 1.0
Seems like a pretty decent little gps unit, assuming i've got it
functioning and configured correctly?
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