[ntp:questions] How to debug PPS?

Chaofu Chen chaofu.chen at yahoo.com
Fri Apr 23 15:37:23 UTC 2010


Problem solved. Seems because I neglect changing "ident" string in kernel config file, so PPS_SYNC option isn't enabled in effect. These are the steps I followed to recompile the kernel:
# cd /usr/src/sys/i386/conf
# cp GENERIC PPSGENERIC
# ee PPSGENERIC
... add options   PPS_SYNC ... [ the only modification ]
# cd /usr/src
# make buildkernel KERNCONF=PPSGENERIC
# make installkernel KERNCONF=PPSGENERIC
# shutdown -r now

This does not bring PPS_SYNC into effect, am I right?

At least, after I change the "ident GENERIC" to "ident PPSGENERIC" in PPSGENERIC file, ntptime returns pplsignal, pplfreq, and ppltime.

--- On Fri, 4/23/10, Chaofu Chen <chaofu.chen at yahoo.com> wrote:

> From: Chaofu Chen <chaofu.chen at yahoo.com>
> Subject: How to debug PPS?
> To: questions at lists.ntp.org
> Date: Friday, April 23, 2010, 12:22 AM
> 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.
> 
> 
> 
>       
> 


      



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