Re: [gpsd-users] Unexpected behavior

[Gary E. Miller]

Yo Nick!

On Thu, 28 Sep 2017 19:36:48 -0700
"Nick Burkitt" <address@hidden> wrote:

> When I have time to jump through the hoops. One could get the
> impression they don’t really want to hear about it.

Ping bzed on gpsd IRC.  He is the Ubuntu packager.

> I am unable to get a cross-compiled application to survive a call to
> gps_open(), whether directly, or via a gpsmm object.

Cross compile is WAY out of my skill set.   And also VERY tool chain
and target specific.  You'll need to post details and hope someone here
can help.

Anything smarter than an Arduino can compile these days.

> In the meantime, I'm concerned that ntpmon shows the jitter of the
> PPS ref clock in the tens to hundreds of microseconds, even after
> running continuously for 24 hours.

Well, that depends on your host, not gpsd.  Your CPU speed, CPU load,
RAM speed, Interrupt latency, KPPS, etc.

A RasPi 3 should be able to well under a micro second.  Limited by
kernel interrupt latency and kernel clock granularity.  As well as the
other stuff just mentioned.

> Is there more I need to do, or am I misreading things?

All depends on your host, host CPU, host load, host IS, kernel config, 
etc.

> Or did I
> misunderstand the accuracy claims?

Nope, any reasonable GPS PPS should be well under a micro second.

> Or is this why you suggested building KPPS into the kernel image,
> instead of making it a loadable module?

I doubt that matters.  Mostly easy of sysadmin to have it one
piece instead of two.

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

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

pgpGk3_lZvvYA.pgp
Description: OpenPGP digital signature