[time] GPS sensor for time synchronization

George Ross gdmr
Thu Jun 1 09:29:03 UTC 2006


> One of the GPS manufacturers has a backwards PPS type signaling.  You flap a 
> signal and it tells you when it saw the transition.  You could use that by 
> flapping a printer port bit.  That might let you get the serial connection 
> over a serial to USB adapter.  Unfortunately, I don't remember who does that. 
>  You can probably find it with a linear search of documentation for the 
> drivers in the NTP package.

Trimble's Acutime (using the palisade driver).  Normally it toggles one of
the modem lines (DCD?).  You want a recent ntpd, as there was a bug
introduced in the 4.1-4.2 transition and later fixed -- here's what's
reported for our one with ntp-4.2.0.b.20051205 on a Dell PE750 with FC3:

     remote           refid      st t when poll reach   delay   offset  jitter
==============================================================================
*GPS_PALISADE(0) .GPS.            0 l   17   16  377    0.000   -0.017   0.005

(We have another S1 with an MSF clock which prefers to synchronise to this 
machine rather than its own local hardware!)
-- 
Dr George D M Ross, School of Informatics, University of Edinburgh
    Kings Buildings, Mayfield Road, Edinburgh, Scotland, EH9 3JZ
Mail: gdmr at inf.ed.ac.uk   Voice: +44 131 650 5147   Fax: +44 131 667 7209
 PGP: 1024D/AD758CC5  B91E D430 1E0D 5883 EF6A  426C B676 5C2B AD75 8CC5


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