Additional pps-gpio

Gary E. Miller gem at
Tue Jan 30 22:12:47 UTC 2018

Yo Achim!

On Tue, 30 Jan 2018 22:45:39 +0100
Achim Gratz via devel <devel at> wrote:

> Gary E. Miller via devel writes:
> > I have some u-blox 6 that are USB mice.  I get under 2 uS jitter on
> > a RasPi, but I have not compared them directly to a GPIO PPS.  I
> > should add that to my long list.  It takes a few days for the
> > clocks to settle in.  
> Both my NaviSys stick (uBlox6) and puck (uBlox8) show ±1ms jitter over
> USB on the raspi. 

> > I just powered up a SkyTrax NS-HP, Venus based.  Took almost 48
> > hours before it reached best accuracy.  
> Huh?  the HP is an RTK receiver so you'd need a reference station to
> make use of that feature set.

Yes, I have two.  But for this test I'm not using that feature set,
just basic PVT.  BTW, that RTK is superb, I can resolve 1 cm changes
when I move the rover!  But not how it is configured right now.

> The timing receiver is the NS-T and
> yes, if it cold starts and needs to pull the Almanach and do a
> auto-survey it'll be busy for a while.

Cold start was a few minutes, had been off for over 5 years, but
48 hours for things to really settle down.  Maybe a factor of 3 better
after the 2 day wait.

I just added a u-blox 6 GPS mouse, and split the SkyTraq PPS to go into
GPIO 4 and GPIO 18.  So three PPS on one RasPi.  I'll post results later
today, first I finish to compiling the new kernel with the new multiple
PPS patch.

Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703
	gem at  Tel:+1 541 382 8588

	    Veritas liberabit vos. -- Quid est veritas?
    "If you can’t measure it, you can’t improve it." - Lord Kelvin
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