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Re: Ubuntu 18.04.3 build from source testing

From: Gary E. Miller
Subject: Re: Ubuntu 18.04.3 build from source testing
Date: Mon, 16 Dec 2019 13:17:18 -0800

Yo Steve!

On Mon, 16 Dec 2019 14:49:52 -0600 (CST)
Steve Bourland <address@hidden> wrote:

> > How long did you wait?  
> I believe "long enough."  The board that interfaces between the
> Garmin and the serial port is blinking it's LED with the PPS, so that
> makes me think it believes it has a fix,

Most GNSS receivers blink PPS before they have a fix.  Most never stop
once they start.

> gpspipe -r indicates:
> $GPRMC,203224.00,A,2926.7278,N,09836.3788,W,0.0258,114.154,010500,4.1,E*70

That is a good PVT.

> My cell phone indicates I'm at latitute 29 degrees, 26 minutes N, 
> longitude 98 degrees, 36 minutes W, so I think that's a solid lock?

Many GPS continue to output a dead reckoning fix after lock loss.

In your case field 3, the "A", says good fix.

> The antenna is sitting on a window sill (inside) of a very large
> window.

I have a south faacing window for my Garmin 18 testing.  The fix comes
and goes.

> Historically, using the Ubuntu packages, xgps has shown a
> very, very long term 3-D fix (tens of thousands of seconds not
> uncommon, I usually try to leave xgps up).

That is good.

> > find /usr -xdev -name -exec ls -l {} \;  
> @wade:~\ % find /usr -xdev -name -exec ls -l {} \;
> -rw-rw-r-- 1 root staff 12456 Dec 11 22:25 
> /usr/local/lib/python2.7/dist-packages/gps/
> -rwxr-xr-x 1 root root 11826 Aug 29  2017 
> /usr/lib/python2.7/dist-packages/gps/

Not good.  You have two for python 2.7, and the old one from the
distro package is the one loaded.  That is your problem.

xgps should have reported the version mismatch.

> > It is very odd that your binary log does not have the Garmin
> > firmware version in it.  This, plus your inability to change
> > between modes, makes my think the data to the receiver is not
> > working.  Broken wire, wrong parity, wrong voltage, etc.  
> Sorry for my lack of experience, but would you expect one direction
> to "work well" (ie, gpspipe seems to be reading data well) while the
> other was messed up?

Yup.  Very common.  Linux does not check incoming parity, but some
GNSS receivers reject messages with bad parity.  Or the signal voltages
are not compatible.  Or the wire is just broken.

> Possible I have a cable issue with the TX wire
> going from the DB-9 to the Garmin I suppose.

Or parity mismatch, or voltage mismatch.

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

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