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Re: Garmin GLO2 with GPSD

From: Gary E. Miller
Subject: Re: Garmin GLO2 with GPSD
Date: Fri, 1 Oct 2021 10:28:17 -0700

Yo Fred!

On Fri, 1 Oct 2021 12:23:59 -0400
"Fred Hillhouse" <> wrote:

> I copied the author of Direwolf.

Cool.  I look forward to helpig them.

> I apologize, I should have provided a better description of the
> receiver.

Given that Garmin does not bother to document it, you can be forgiven.

> The Garmin GLO 2 (and the 'Dual XGPS160') can provide data
> sentences to four Bluetooth users at the same time. I used the term
> 'channel' to describe the connection for a user. After thinking about
> this, 'port' might be a better term. On a Windows PC. Using PuTTY, I
> happen to see NMEA sentences. 

On the internet a "port" is a TCP or UDP port.  You are best to just say
"connection" or "BT connection".

> Trimmed content that is not really contributing.
> >> Direwolf acquires data from GPSD. It never sees a (constant) valid
> >>  
> position. My
> >> suspicion is that the connection between rfcomm and GPSD is not
> >> complete.  
> Added 'constant' above for clarity.
> Is it possible I need to pipe(?) the rfcomm output to TTY so the Baud
> possibly could be regulated?

As I said before, if you have lat/lon, then you have a good connections.
Stop worrying about what already works.

> At the RPi CLI: gpsd -V results in gpsd: 3.17 (revision 3.17)

Wow, that is 4 years old.  You need to update that.  3.23.1 is current.

> I assume that it the server.

No assumption needed.  That is the server.

> As far as the 'client' part, I don't
> know.

Same drill: cgps -V

> > >You said you never got status?  But there it is.  You have a 3D
> > >fix, and you just got it (not old).    
> Yes, according to cgps, I just got it, but, it has been there all day
> long. 

Even better, you had a fix for all day.  Why is that a problem?

> On a different device monitoring a serial port (Bluetooth to COMport),
> capturing sentences with PuTTY, connected to the same GPS, at the
> same time, there is never a loss of 3D status!

Good.  What's the problem?

> However, using cgps, it is in 2D, then 3D, then 2D, then 3D:

a) you are using a really old gpsd/cgps.
b) look closely at your NMEA, that is what you NMEA says.

> >So, again, what is the problem?  
> Direwolf writes text to the terminal window for every change in
> status. That in itself is not a problem, unless the status is
> constantly changing. So, I see an endless stream of:
> GPSD: Location Fix is now 2D
> GPSD: Location Fix is now 3D
> GPSD: Location Fix is now 2D
> GPSD: Location Fix is now 3D
> GPSD: Location Fix is now 2D
> GPSD: Location Fix is now 3D
> It never ends.

And that is correct, but naive.  Best to wait for the enitre epoch to arrive
before warningong about mode changes.

Data in NMEA come to gpsd in inconsistent dribs and drabs during the
fix epoch (usually on second).  So gpsd has little choice but
to similarly dribble it back out to the client.

> >Ah, that is a good thing.  Old fixes are not good, a fresh new fix
> >is good. If you want old fixes, turn off your GPS.  
> I understand but what happens when your GPS is connected and you use
> cgps to examine the "Status"? Does your "Status" increment as time
> passes?

Yes, becasue I do not use NMEA.

> As I understand it, it increases with time and drops back to
> 0 if the status is 2D. Of course my understanding can be flawed.

It drops back to zero on every change.  And yours changines at least
twice a seceond.  cgps is just reporting that.

> >If you are getting very fresh and current updates, that cannot
> >possibly be a connection issue.  
> A fresh update of 2D with the following of 3D, repeating non-stop,
> still doesn't seem right.

There is no "right" or "wrong".  There is just what your receiver
is telling gpsd (you).

> That is the symptom. I can't identify the
> problem. 

Yup, you can't id the problem because their is none.  Except your
old gpsd version.

Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703  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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