Hi folks,
Is anyone happily running a stratum 1 NTP server with a GPS with a PPS
signal on NetBSD 6?
I've got a Garmin GPS18x on a Soekris net4801 where the GPS clock has
a funny offset. Here's the output from "ntpq -pn":
remote refid st t when poll reach delay offset jitter
==============================================================================
127.127.20.0 .PPS. 0 l 14 16 17 0.000 -658.75 6.388
192.168.0.1 27.50.90.253 3 u 11 64 3 0.348 -0.594 0.166
192.168.0.42 192.168.0.1 4 u 10 64 3 0.345 5.670 0.200
202.191.108.73 47.187.174.51 2 u 8 64 3 30.141 -2.695 0.401
59.167.170.228 203.35.83.242 2 u 11 64 3 55.362 -1.997 1.068
27.50.90.253 202.46.181.123 2 u 8 64 3 36.167 0.108 0.162
The GPS clock offset appears to be reasonably random (but seems to like
between -800 and -600 more often than not), but is then pretty much
constant for each ntpd invocation.
I've thrown some debugging in ntpd, and the offset is very suspiciously
close to the time the PPS info was read from the kernel (the "now") and
not the time of the PPS timestamp (the "assert ts"):
time_pps_fetch: now = 1374192482.658097 assert ts = 1374192480.999648384
time_pps_fetch: now = 1374192484.675356 assert ts = 1374192482.990470645
time_pps_fetch: now = 1374192486.656708 assert ts = 1374192484.990341144
time_pps_fetch: now = 1374192488.659388 assert ts = 1374192487.005927355
My ntp.conf has this:
server 127.127.20.0 mode 1 minpoll 4 maxpoll 4
fudge 127.127.20.0 flag1 1 flag3 1 refid PPS
I've tried various modes to select different NMEA sentences without any
effect, and having flag3 (use kernel pps) set to 0 also has no effect.
With a NetBSD 5 userland and kernel, all is much happier:
remote refid st t when poll reach delay offset jitter
==============================================================================
*127.127.20.0 .PPS. 0 l 13 16 377 0.000 0.002 0.004
-192.168.0.42 192.168.0.1 4 u 53 64 77 0.371 -7.618 0.924
-192.168.0.1 27.50.90.253 3 u 48 64 77 0.379 -6.047 1.768
-54.252.129.186 149.20.64.28 2 u 38 64 77 33.982 -9.149 1.730
+202.125.45.77 223.252.32.9 2 u 40 64 77 47.374 -2.040 1.800
-202.191.108.72 47.187.174.51 2 u 42 64 77 29.762 -8.068 1.379
I've also tried the netbsd-5 version of ntp on netbsd-6, and that has the
same offset problem as native ntpd.
The PPS bits of the com driver and inside sys/kern don't appear to be
different in any obvious way. I'm about to start looking at the 64-bit
time_t change.
Anyone have any ideas or suggestions?