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Re: [RFC] get gpsd to work with gnss-share

From: Gary E. Miller
Subject: Re: [RFC] get gpsd to work with gnss-share
Date: Mon, 9 Jan 2023 13:13:24 -0800

Yo Pavel!

On Mon, 9 Jan 2023 22:02:52 +0100
Pavel Machek <> wrote:

> > > The real value in gnss-share is that it can
> > > perform any arbitrary setup for specific devices, or interrupt
> > > them to do things like load a-gps, etc. It also supports any
> > > number of clients connected to the socket at once all receiving
> > > the same unaltered data from the module.  
> > 
> > I find A-GPS near useless with the most modern devices.  Until
> > recently the vendors refused to even document the process.  
> It really depends on antena quality etc. PinePhone has very bad GPS
> reception, and Librem 5 is not too great either (there may be hardware
> improvements pending in that case). A-GPS should be useful there. On
> many phones GPS reception is not really useful without A-GPS, as noone
> tested that variant.

I can't speak to the PinePhone, but my tests have never shown an
advantage to A-GPS on a modern multi-constellation receiver.

If you feel otherwise, I'd love to see some A/B testing.

> > > > So you are not on Android?  I guess I am lost...    
> > > 
> > > No, this is postmarketOS, but there are other Linux distros (so
> > > far I know of PureOS too) that are not Android that also use
> > > gnss-share.  
> > 
> > Would have been helpful to have known that up front.  No context was
> > given in the original request.  
> Sorry about that.

Pretty much normal here.

> > Echoed char by char?  Sentence by sentence?  Buffered?

No answer?

> > > $PSTMCPU,60.50,-1,49*4C  
> > Proprietary sentence.  Got any doc on that?  ST Micro?  
> Actually yes, I can find docs on that; but this is not really
> gnss-share specific, but specific to the hardware it runs on.

Yup, and gpsd tries to run on (most) everything.

> This sentence is documented here:

Thanks!  I'll add that to my TODO list.

> ...but I'm not sure if this is exact module we have.

Which is why, as that doc tells you, your versions stuff is sent in
$PMSTVER messages.  So you already have that info.

> > > $GPGGA,xxxxxx,xxxx.xxxxx,N,xxxx.xxxxxx,W,0,00,99.0,025.15,M,0.0,M,,*7B
> > >  
> > 
> > I can't run tests on corrupted data like that.  
> Should I gather longer logs?

Not if they are corrupted like that.  Longer is not much better, varied
is much better.  Like startup -> signal lock -> signal loss -> signal lock.

> Anyway, gnss-share will provide whatever data kernel provides it, so
> logs will be valid for Librem 5, but gnss-share will likely be used on
> other hardware, too.

Welcome to gpsd, a big game of whack-a-mole.  The $PMSTVER would be nice
to have.

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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