[Thumbgps-devel] [gpsd-dev] PPS over USB

[Eric S. Raymond]

Ron Frazier (NTP) <timekeepingntplist at techstarship.com>:
> Just wondering.  On the USB + PPS + PL2303 concept, has the long
> term variation that has been observed in NMEA data in other similar
> units without PPS been accounted for?

No.  Hal Murray and I studied this extensively and were unable to
get a handle on the cause.

>                                      I have personally observed a
> variation in NMEA data on my Globalsat Sirf III USB device of up to
> +/- 70 ms over several days.  Will having the PPS coming though USB
> solve that problem?

Yes.  The measured jitter of 1PPS over PL2303 USB is 0.5 milliseconds.
-- 
		<a href="http://www.catb.org/~esr/">Eric S. Raymond</a>