[ntp:hackers] Using NMEA+PPS on multiple servers

David J Taylor david-taylor at blueyonder.co.uk
Mon Feb 23 10:29:20 UTC 2009


Terje Mathisen wrote:
[]
> It is indeed possible to run NMEA+PPS to multiple servers, by
>  connecting only the DCD and RX line to all the secondary servers,
> with the primary having a TX conection as well to be able to send the 
> initial
> setup command.
>
> This is because the driver does not _have_ to send anything to the
> GPS, the GPS will instead send the RMC (or one of the other strings
> that provide all the needed info, personally I prefer to use GGA
> which gives me a record of the number of sats, the current HDOP and
> the currently calculated position in the clockstats file:
>
> no115350bsd# tail -5 /var/log/ntp/clockstats ; ntpq -c rv -p
> 54885 33208.310 127.127.20.0
> $GPGGA,091328,5955.4865,N,01040.8319,E,1,05,3.0,6.9,M,39.7,M,,*42
[]
> Terje

Thanks, Terje, that's good to know.  I recall writing a small Windows 
program to set up my GPS18 LVC before connecting it to the FreeBSD box 
which runs ntp.  It makes it send just $GPRMC sentences, which was the 
"minimum recommended", but I can see the value in the satellite count as 
well.

If all goes well with Dave Hart's work well, I may be able to power-down 
the FreeBSD box for good, and just distribute my PPS signal as a DCD line. 
Pure serial on Windows was worse than syncing from the Internet!

Cheers,
David
-- 
SatSignal software - quality software written to your requirements
Web:  www.satsignal.eu
Email:  davidtaylor at writeme.com 




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