[ntp:questions] help with setting up NTP on windows with a USB GPS

jack j.jack.wang at gmail.com
Fri Nov 27 18:35:42 UTC 2009


Just to let everyone know that the u-blox GPS works well now. The
offset is 0.02ms with jitter at 0.002ms. My other GPS with only USB
out has an offset of 5ms and jitter of 2.5ms.

Jack

On Nov 27, 11:17 am, David Lord <sn... at lordynet.org> wrote:
> jack wrote:
>
> > You assumed right. I did start with a USB emulated port. The GPS I
> > bought is from U-Blox and it has both USB and serial output. The
> > serial output has the 1PPS signal (with an LED indicator). I thought I
> > would start with the USB output since it's rather hard to find a
> > computer with a serial port. Also I would like to see the accuracy by
> > using the USB port only. I later switched to a machine with a serial
> > port and started using the serial output of the U-Blox GPS device and
> > 1PPS. My objective is to use two of these devices to sync two separate
> > computers to within ms so they can share time-sensitive data (time
> > stamped).
>
> > I left the device running overnight and I noticed it computed an
> > offset at one time. It's currently not updating (everything is zero
> > now). I will read carefully what Dave Hart said and follow his advice.
>
> > Thanks to everyone for your help.
>
> Mostly here with convenient location for the gps, with Garmin
> gps18x-lvc I had a few failed updates where reach dropped from
> 377 (avg offset about 2us), whilst with GS-BR-304 there isn't
> anywhere near as good reception and there were many periods
> where reach was back to 0 (avg offset about 10ms).
>
> Have you connected with hyperterm or similar to check the serial
> gps output?
>
> Possibly you aren't picking up enough sats to get a fix. In that
> case you need to site the gps in a better location for reception,
> and/or give the gps your exact geographic coordinates.
>
> David




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