[ntp:questions] YEA! My Sure Electronics GPS just arrived.
David J Taylor
david-taylor at blueyonder.co.uk.invalid
Sat Mar 24 11:05:13 UTC 2012
> I now have the PPS circuit working on the Sure board. I have not
> soldered it yet. I just taped a jumper wire between the PPS test point
> at the edge of the board and the DCD pin 1 on the RS-232 port. The
> serial data is coming in through the Trendnet TU-S9 serial - USB
> converter, which is passing DCD. I'm getting + .5 / - 1.5 ms offsets.
> The PPS is nowhere to be seen on the statistics screen, but it is
> obviously working. I don't know why it's not more centered around zero,
> and maybe that will change. However, my total peak to peak range of
> offset variance is 2 ms, and that's coming through USB. If I can
> maintain that level of accuracy, and it's consistent with UTC, then I'm
> very happy. That's plenty good for my purposes. I still may try to run
> it through a real serial port on another machine just for kicks.
Yes, those were the sorts of figures I was seeing.
The jitter I saw was about 45 microseconds for the USB/PPS against 2.3 - 3
microseconds for various serial-port/PPS. All figures from Windows XP.
If the graphs there are anything to go by it seems that the offset varied
between -0.15 to +0.3 milliseconds (very approximately).
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