Re: [gpsd-dev] [Thumbgps-devel] Progress on Plain Jane

[Gary E. Miller]

Yo Eric!

On Tue, 1 May 2012 19:09:17 -0400
"Eric S. Raymond" <address@hidden> wrote:

> Gary E. Miller <address@hidden>:
> > As you can see the NMEA/USB short term jitter is about 2 milliSec
> > and the PPS/USB time is about 0.5 milliSec jitter.  Long term
> > NMEA/USB drift is quite a bit larger, maybe 100 milliSec or more.
> > 
> > So the jitter of PPS over USB is about 50x worse than PPS over
> > GigE, but I think for the purposes at hand pretty good.  Of course
> > I expect the results to be worse when run on a single core router.
> 
> That's excellent news.  0.5msec jitter is as good as we could have
> expected and exactly what one would predict from a max error of 1msec
> due to polling interval. The long-term NMEA/USB drift is consistent
> with previous observations by Hal Murray and myself.

Nice when theory and practice agree.  I wonder if there is a USB 2.0
equivalent of the PL2303 which would give us a 125 microSec poll?

Might be worth asking navisys about that.

> Do you consider the GR-601 with this mod to be ready for production?
> Should we give Navisys the green light on GPSD compatibility?  I see
> no reason not to at this point, but you're doing the testing so you
> make the call.

So far so good.  I'd like to play with them a few days first.  Shoot
me your mailing list and I'll snail mail you one so you can see for
yourself.


BTW, when I email the list I am often rejected, so if you do not see
it from the thumbgps lkist shortly please forward a copy.

RGDS
GARY
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Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97701
        address@hidden  Tel:+1(541)382-8588

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