Re: [gpsd-users] Enable PPS Echo

[Gary E. Miller]

Yo Reto!

On Tue, 5 Apr 2016 20:11:00 +0000
Reto Zbinden ST <address@hidden> wrote:

> Many thanks for your fast response. I've tried to catch a lot of
> samples and did some statistics to get a more usable result, but an
> internet source isn't really a good choice for such a comparison.
> That's why I'm looking for a way to do some more accurate
> measurements (using some commonly available tools).

If you find some, tell us, computers on a chip makes it hard to 
pin down latency issues.

> My feeling is, that the delay could be
> introduced by the PPS / interrupt processing on the ALIX board or the
> serial port itself.

Yup, and if you care, your are using KPPS, and not just PPS.

> I thought that the PPS echo function which
> generates an event on the RTS line could be handy to verify my theory.

It could, if your GPS supports it.  I have a pile of GPS and I don't think I
have any with that function.  Does yours?  If so, I'd like the model
number.

We'd need to create a tool to send the echo and measure the return, both
as PPS and as KPPS, but that would not be hard.

RGDS
GARY
---------------------------------------------------------------------------
Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703
        address@hidden  Tel:+1 541 382 8588

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