[ntp:questions] Re: Garmin gps18: The best DIY gps refclock?
jpp at cloudview.com
Mon Nov 28 17:58:57 UTC 2005
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Roman Mäder wrote:
> Eugen COCA wrote:
>>Any indication about connecting the PPS signal and setting up the ntpd
>>service to work with ?
>>Thank you !
>>P.S. I think the 1 us jitter is true only if using the PPS signal.
> I did configure the PPS device in addition to the NMEA refclock,
> but it does not give me any additional accuracy.
> this "ntpq -p" output is typical:
> remote refid st t when poll reach delay offset jitter
> +GPS_NMEA(0) .GPS. 0 l 25 64 377 0.000 -0.036 0.020
> oPPS(0) .PPS. 0 l 43 64 377 0.000 -0.046 0.030
> configured as:
> server 127.127.20.0 mode 2 prefer
> server 127.127.22.0
> fudge 127.127.22.1 flag3 1
The NMEA driver (20) has PPS code built in so you don't need the stand
alone PPS driver (22) - that's why you don't see any difference. If
you remove the link to pps0 from /dev and restart ntpd you'll see the
non PPS results (not even close to the PPS numbers).
John (also using a GPS18LVC)
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