On 28 December 2013 22:40, Adrian P <mailing-li...@pascalau.ro> wrote:
> How do I know that my NTP server is actually using the PPS signal from
> my Garmin GPS 18x LVC?
Thanks for all the answers.
After some more reading, I found out that I could use the following
commands to see if PPS signal is used by NTP or not:
[root@freebsd ~]# ntptime
ntp_gettime() returns code 0 (OK)
time d67129d6.25c8a798 Fri, Jan 3 2014 14:21:42.147, (.147593763),
maximum error 5735 us, estimated error 2 us, TAI offset 0
ntp_adjtime() returns code 0 (OK)
modes 0x0 (),
offset 1.879 us, frequency 53.124 ppm, interval 32 s,
maximum error 5735 us, estimated error 2 us,
status 0x2107 (PLL,PPSFREQ,PPSTIME,PPSSIGNAL,NANO),
time constant 4, precision 0.001 us, tolerance 496 ppm,
pps frequency 53.124 ppm, stability 0.242 ppm, jitter 2.613 us,
intervals 17, jitter exceeded 5, stability exceeded 0, errors 3.
[root@freebsd ~]#
[root@freebsd ~]# ntpdc -c kerninfo
pll offset: 3.51e-06 s
pll frequency: 53.124 ppm
maximum error: 0.000241 s
estimated error: 4e-06 s
status: 2107 pll ppsfreq ppstime ppssignal nano
pll time constant: 4
precision: 1e-09 s
frequency tolerance: 496 ppm
pps frequency: 53.124 ppm
pps stability: 0.242 ppm
pps jitter: 1.507e-06 s
calibration interval: 32 s
calibration cycles: 17
jitter exceeded: 5
stability exceeded: 0
calibration errors: 3
[root@freebsd ~]#
Basically both ntptime and ntpdc -c kerninfo commands have a status
line that tells if PPS signal was detected or not. If for some reason
there is a problem with the PPS signal, the output of the above
commands would look something like below, and as you could see there
is no PPSSIGNAL mentioned in the status line.
[root@freebsd ~]# ntptime
ntp_gettime() returns code 0 (OK)
time d67128f0.525d28b4 Fri, Jan 3 2014 14:17:52.321, (.321734654),
maximum error 107516 us, estimated error 16 us, TAI offset 0
ntp_adjtime() returns code 0 (OK)
modes 0x0 (),
offset 0.000 us, frequency 34.328 ppm, interval 4 s,
maximum error 107516 us, estimated error 16 us,
status 0x2001 (PLL,NANO),
time constant 3, precision 0.001 us, tolerance 496 ppm,
pps frequency 34.328 ppm, stability 0.000 ppm, jitter 0.000 us,
intervals 0, jitter exceeded 0, stability exceeded 0, errors 0.
[root@freebsd ~]#
[root@freebsd ~]# ntpdc -c kerninfo
pll offset: 0 s
pll frequency: 34.328 ppm
maximum error: 0.110016 s
estimated error: 1.6e-05 s
status: 2001 pll nano
pll time constant: 3
precision: 1e-09 s
frequency tolerance: 496 ppm
pps frequency: 34.328 ppm
pps stability: 0.000 ppm
pps jitter: 0 s
calibration interval: 4 s
calibration cycles: 0
jitter exceeded: 0
stability exceeded: 0
calibration errors: 0
[root@freebsd ~]#
Furthermore, now I also got the "o" tally code in the output of ntpq
-p command, but I had to go back on using FreeBSD (version 9.2) and
only the NMEA GPS receiver driver 127.127.20.x without the ATOM driver
127.127.22.x.
server 127.127.20.0 mode 1 minpoll 4 maxpoll 4 prefer
fudge 127.127.20.0 flag1 1 flag2 0 flag3 1 refid PPS
[root@freebsd ~]# ntpq -p -c rv
assID=0 status=0415 leap_none, sync_uhf_clock, 1 event, event_clock_reset,
version="ntpd 4.2.6p5@1.2349-o Thu Dec 12 07:01:03 UTC 2013 (1)",
processor="i386", system="FreeBSD/9.2-RELEASE-p2", leap=00, stratum=1,
precision=-19, rootdelay=0.000, rootdisp=0.427, refid=PPS,
reftime=d6712d5b.9ddd9581 Fri, Jan 3 2014 14:36:43.616,
clock=d6712d68.0ce8c920 Fri, Jan 3 2014 14:36:56.050, peer=55434,
tc=4, mintc=3, offset=-0.012, frequency=53.137, sys_jitter=0.002,
clk_jitter=0.001, clk_wander=0.087
remote refid st t when poll reach delay offset jitter
==============================================================================
oGPS_NMEA(0) .PPS. 0 l 13 16 377 0.000 -0.012 0.002
[root@freebsd ~]#
For some reason on latest Debian Linux I was not able to get this working...
Best regards,
Adrian
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