[ntp:questions] How to debug GPS PPS?

Thomas Laus lausts at acm.org
Tue Feb 16 22:01:06 UTC 2010


On 2010-02-16, xyz-2041 <xyz2041 at gmail.com> wrote:
>
> Thanks, Tom and guys.  I really appreciate your help!
>
> Looks like something is going on with the Oncore:
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> # ntpq -c pe
>      remote           refid      st t when poll reach   delay
> offset  jitter
>==============================================================================
>  GPS_ONCORE(0)   .GPS.            0 l    -   16    0    0.000
> 0.000   0.000
> xPPS(0)          .PPS.            0 l   11   64  377    0.000
> -3.085   0.017
>  192.168.2.255   .BCST.          16 u    -   64    0    0.000
> 0.000   0.001
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> # ntpq -c rv
> assID=0 status=0615 leap_none, sync_ntp, 1 event, event_clock_reset,
> version="ntpd 4.2.7p19 at 1.2108-o Mon Feb 15 20:10:40 UTC 2010 (1)",
> processor="i386", system="FreeBSD/7.2-RELEASE", leap=00, stratum=2,
> precision=-20, rootdelay=44.827, rootdisp=44.339, refid=192.43.244.18,
> reftime=cf25709c.1130eea8  Tue, Feb 16 2010 13:29:32.067,
> clock=cf257657.3d54896e  Tue, Feb 16 2010 13:53:59.239, peer=54924,
> tc=10, mintc=3, offset=-4.877, frequency=-49.876, sys_jitter=1.658,
> clk_jitter=2.179, clk_wander=0.056
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>
>
> "precision=-20" how does one interpret this?
>
> Why wouldn't the PPS be taken as preferred?
>
> /var/log/ntp/clockstats:
> http://www.a7h.com/~stuph/var--log--ntp--clockstats-2010-Feb-16.txt
>
> Contained in /etc/ntp.conf:
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> # GPS Oncore driver
> # server 127.127.30.0  prefer
>

One note about your configuration, I don't think that you can
have two 'prefer' statements.  It was discussed recently in this
newsgroup and my memory of recent events is not as good as it used to
be.  Try restarting your Oncore without the pps driver.  Mine seems to
see the receiver pps without having that statement in my /etc/ntp.conf
file.  It still looks like your Oncore receiver is not seeing the data
being requested by the ntp refclock driver.  Can you post the Oncore
related lines of your syslog?  The driver does a lot of setup work after
a restart and the results are sent to the log.  It may provide some
insight into what is happening.  Your Oncore pps on the DCD pin is doing
something, but the rest of the data is still not getting seen by the
daemon. Precision of -20 is what I see on my setup. 

Tom


-- 
Public Keys:
PGP KeyID = 0x5F22FDC1
GnuPG KeyID = 0x620836CF




More information about the questions mailing list