[ntp:questions] PPS signal from Garmin GPS 18x LVC

David Taylor david-taylor at blueyonder.co.uk.invalid
Sun Dec 29 05:59:45 UTC 2013


On 28/12/2013 20:40, Adrian P wrote:
> Hi,
>
> How do I know that my NTP server is actually using the PPS signal from
> my Garmin GPS 18x LVC?
>
> I have the following NMEA driver configured in /etc/ntp.conf:
>
> 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
>
> The below output shows me that NTP is using the NMEA GPS clock,
> however I cannot find anywhere a command that tells me that PPS signal
> is used as well...
>
> root at debian:~# ntpq -c clockvar
> associd=0 status=00f1 , 15 events, clk_no_reply,
> device="NMEA GPS Clock",
> timecode="$GPRMC,202549,A,xxxx.2257,N,xxxxx.2075,E,000.0,195.2,281213,004.8,E,A*1D",
> poll=13, noreply=36, badformat=0, baddata=0, fudgetime1=0.000, stratum=0,
> refid=PPS, flags=5
> root at debian:~#
>
> Many thanks,
> Adrian

Adrian,

My understanding is that a "o" as the tally code in the output from ntpq 
-pn indicates PPS sync.  On the two systems here fed from a GPS 18 LVC, 
with some line omitted:

FreeBSD PC Pixie:

server  127.127.20.1    mode 0  minpoll 4 maxpoll 4  prefer
fudge   127.127.20.1    flag1 1 flag3 1 refid PPS

C:\Users\David>ntpq -crv -pn pixie
associd=0 status=041f leap_none, sync_uhf_radio, 1 event, 
stale_leapsecond_values,
version="ntpd 4.2.7p406 at 1.2483 Sat Dec 28 16:28:47 UTC 2013 (1)",
processor="i386", system="FreeBSD/8.2-RELEASE-p6", leap=00, stratum=1,
precision=-19, rootdelay=0.000, rootdisp=1.000, refid=PPS,
reftime=d66a36ed.19d84794  Sun, Dec 29 2013  5:51:41.100,
clock=d66a36ed.b372d389  Sun, Dec 29 2013  5:51:41.700, peer=32026, tc=4,
mintc=3, offset=0.007628, frequency=28.823, sys_jitter=0.001907,
clk_jitter=0.003, clk_wander=0.007, tai=35, leapsec=201207010000,
expire=201312010000
      remote           refid      st t when poll reach   delay   offset 
  jitter
==============================================================================
o127.127.20.1    .PPS.            0 l    -   16  377    0.000    0.008 
  0.002
_____________________________________


Windows 2000 PC Bacchus:

server	127.127.22.1	minpoll 4		# atom PPS driver
server	127.127.20.1	minpoll 4	# NMEA serial Garmin GPS 18LVC
fudge	127.127.20.1	refid NMEA

C:\Users\David>ntpq -crv -pn bacchus
associd=0 status=01ff leap_none, sync_pps, 15 events, 
stale_leapsecond_values,
version="ntpd 4.2.7p348 at 1.2891-o Jan 18 13:50:53 (UTC+01:00) 2013  (5)",
processor="x86", system="Windows", leap=00, stratum=1, precision=-18,
rootdelay=0.000, rootdisp=1.030, refid=PPS,
reftime=d66a370c.88361a9d  Sun, Dec 29 2013  5:52:12.532,
clock=d66a370e.e893b45c  Sun, Dec 29 2013  5:52:14.908, peer=34194, tc=4,
mintc=3, offset=0.001361, frequency=-5.945, sys_jitter=0.047802,
clk_jitter=0.054, clk_wander=0.001, tai=35, leapsec=201207010000,
expire=201212280000, ctr_frequency=4.19
      remote           refid      st t when poll reach   delay   offset 
  jitter
==============================================================================
o127.127.22.1    .PPS.            0 l    3   16  377    0.000    0.001 
  0.048
+127.127.20.1    .NMEA.           0 l    1   16  377    0.000   -0.051 
  0.041
_____________________________________

and one fed from a GPS 18x LVC, Windows PC Stamsund:

server	127.127.22.1	minpoll 4	# PPS using serialpps.sys
fudge   127.127.22.1    refid PPS  flag3 1
server	127.127.20.1	minpoll 4  mode 33  # 19200bps, NMEA serial port
fudge	127.127.20.1	refid NMEA

C:\Users\David>ntpq -crv -pn stamsund
associd=0 status=011f leap_none, sync_pps, 1 event, stale_leapsecond_values,
version="ntpd 4.2.7p406 at 1.2483-o Dec 28 16:04:29.64 (UTC-00:00) 2013  (1)",
processor="x86", system="Windows", leap=00, stratum=1, precision=-22,
rootdelay=0.000, rootdisp=1.225, refid=PPS,
reftime=d66a375c.3e52fa96  Sun, Dec 29 2013  5:53:32.243,
clock=d66a376b.d26fb21b  Sun, Dec 29 2013  5:53:47.822, peer=46859, tc=4,
mintc=3, offset=0.088931, frequency=-6.839, sys_jitter=0.034536,
clk_jitter=0.026, clk_wander=0.001, tai=35, leapsec=201207010000,
expire=201312010000
      remote           refid      st t when poll reach   delay   offset 
  jitter
==============================================================================
o127.127.22.1    .PPS.            0 l   15   16  377    0.000    0.089 
  0.035
+127.127.20.1    .NMEA.           0 l   14   16  377    0.000    0.021 
  0.018
_____________________________________


I hope that helps!

-- 
Cheers,
David
Web: http://www.satsignal.eu



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