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

David Lord snews at lordynet.org
Fri Nov 27 16:17:06 UTC 2009


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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