Additional pps-gpio

[Achim Gratz]

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 plan to pull out the PPS from the puck some time
now that I can use a second PPS.

The NavSpark Freebie had ±10ms on my PC, but I don't really know how
well the PL2303 driver it was using works (for starters, I don't think
anything changed with setting the low_latency option on the interface).
I might test the interface from the Freebie again on a rasPi later on,
but I don't think it'll come out any better.

With PPS over virtual serial I get around ±40µs in total, although
there's a noticeable double distribution.  I don't have enough data yet
to see what's really going on, but it looks like the larger cluster
shows around 10µs width over the last hour.

> 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.  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.


Regards,
Achim.
-- 
+<[Q+ Matrix-12 WAVE#46+305 Neuron microQkb Andromeda XTk Blofeld]>+

SD adaptation for Waldorf rackAttack V1.04R1:
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