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Re: [gpsd-users] Large ntp.conf time1 offset needed with GPSD shared mem

From: Gary E. Miller
Subject: Re: [gpsd-users] Large ntp.conf time1 offset needed with GPSD shared memory driver
Date: Wed, 10 Aug 2016 11:27:57 -0700

Yo Jon!

On Wed, 10 Aug 2016 02:11:26 -0500
"Jon Brase" <address@hidden> wrote:

> > Have you looked at the RasPi HOWTO?  
> Which RasPi HOWTO are you referring to.

Well, the one that gpsd and ntpsec have been working on:

Plus more info in the gpsd howtos in the tar ball:


> Different ones recommend different
> setups.

It is Unix, many way to skin the cat.

> Anything that recommended using 28.0 and 28.1 has come to
> grief trying to get GPSD to pick up PPS on the Pi

Well, that is just wrong.  Driver 28 is the best way.

> Using 28.0 and
> 22.0 seems to work best of everything I've tried

It has weird failure modes.  Get some day/week/month graphs and you'll see.

> > Which makes it real easy to get the PPS on the wrong second.  Or
> > worse, following PPS when the PPS is not valid.  
> But that's the point of the offset fudge on the coarse data, right?

Half way.  Driver 22 has no way of knowing when the PPS is invalid.  It
will follow a bad PPS into the weeds.

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

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