[ntp:questions] How to debug PPS?
David Lord
snews at lordynet.org
Thu Apr 22 21:27:37 UTC 2010
Chaofu Chen wrote:
> Hi all. I want to build a NTP server but PPS doen't work for the time being. Status bits from "ntptime" and "ntpdc -c kern" include PLL and NANO, sometimes PPSTIME and PPSFREQ, but PPSSIGNAL never appears.
>
> ------- system overview ---------------
> MotherBoard: Intel Atom N270 / Intel 945GSE+ICH7M
> OS: FreeBSD 7.2R, kernel recompiled with option PPS_SYNC
> NTP: v4.2.6p1
> PPS: -8.6v ~ +7.7v, 1Hz, pulse width 500ms
> Time source: GGA sentense from GPS module, 9600bps, through cuad0
> ------- ntp.conf -------------
> server 127.127.20.1 mode 18 prefer
> fudge 127.127.20.1 flag1 1 flag2 1 flag3 1
> ...
> -------- output of ntpq ----------------------
> ntpq>pe
> remote refid st t when poll reach delay offset jitter
> ==============================================================================
> *GPS_NMEA(1) .GPS. 0 l 53 64 377 0.000 -4.503 8.626
> ntpq>as
> ind assid status conf reach auth condition last_event cnt
> ===========================================================
> 1 18533 9644 yes yes none sys.peer reachable 4
> ntpq>rv
> associd=0 status=042d leap_none, sync_uhf_radio, 2 events, kern,
> version="ntpd 4.2.6p1 at 1.2158-o Thu Apr 22 13:28:36 UTC 2010 (1)",
> processor="i386", system="FreeBSD/7.2-RELEASE", leap=00, stratum=1,
> precision=-18, rootdelay=0.000, rootdisp=13.349, refid=GPS,
> reftime=cf7ad712.6e321a44 Thu, Apr 22 2010 22:09:22.430,
> clock=cf7ad712.7f655c3a Thu, Apr 22 2010 22:09:22.497, peer=18533, tc=6,
> mintc=3, offset=-4.111, frequency=-4.879, sys_jitter=7.301,
> clk_jitter=0.000, clk_wander=0.006
> ntpq>cv
> associd=0 status=0000 , no events, clk_unspec,
> device="NMEA GPS Clock",
> timecode="$GPGGA,140929,3130.8506,N,10444.6118,E,1,09,0.9,529.2,M,-32.4,M,,*60",
> poll=17, noreply=0, badformat=0, baddata=0, fudgetime1=0.000, stratum=0,
> refid=GPS, flags=5
> ---------- output of ntpdc -c kern -------
> pll offset: -0.00395776 s
> pll frequency: -4.879 ppm
> maximum error: 0.032849 s
> estimated error: 0.003847 s
> status: 2007 pll ppsfreq ppstime nano
> pll time constant: 6
> precision: 1e-09 s
> frequency tolerance: 496 ppm
> ---------- output of ntptime -----------
> ntp_gettime() returns code 5 (ERROR)
> time cf7ad741.5a770bb0 Thu, Apr 22 2010 22:10:09.353, (.353379029),
> maximum error 36849 us, estimated error 3847 us, TAI offset 0
> ntp_adjtime() returns code 5 (ERROR)
> modes 0x0 (),
> offset -3926.940 us, frequency -4.879 ppm, interval 1 s,
> maximum error 36849 us, estimated error 3847 us,
> status 0x2007 (PLL,PPSFREQ,PPSTIME,NANO),
> time constant 6, precision 0.001 us, tolerance 496 ppm,
> ---------------------------------------------------
>
> Any suggestions or help will be appreciated.
I don't see anywhere in above where your PPS is coming from.
It's unlikely it will be from any GPS sentence as these can
be anywhere within a second for the devices I have here.
If you have a PPS signal on serial DCD, I'd suggest adding
pps driver "server 127.127.22.(n)"
which requires /dev/pps(n)
Here on NetBSD I have /dev/pps2 -> /dev/tty00
I think the NMEA driver may pickup the PPS so long as /dev/pps(n)
is available.
remote refid st poll reach offset jitter
*GPS_NMEA(2) .GPSb. 0 64 377 0.001 0.004
oPPS(2) .PPSb. 0 16 377 -0.002 0.004
David
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