Re: [gpsd-users] Polling for GPS data using python3 API

[Gary E. Miller]

Yo pisymbol!

On Tue, 13 Aug 2019 15:19:01 -0400
"pisymbol ." <address@hidden> wrote:

> On Tue, Aug 13, 2019 at 3:09 PM Gary E. Miller <address@hidden> wrote:
> 
> > Yo pisymbol!
> >
> > On Tue, 13 Aug 2019 15:03:42 -0400
> > "pisymbol ." <address@hidden> wrote:
> >  
> > > > The samples are buffering because you are not reading them.  You
> > > > need to keep up with the incoming messages.
> > > >  
> > >
> > > Yes, I see that and now that is what I'm doing. I wrote a poller
> > > process that is just reading samples continuously (no sleep)
> > > and emits a sample into shared memory for other threads to pick
> > > up. The change is being tested as I write this to see if the
> > > "lag" issue disappears that I saw on 3.9.  
> >
> > You shoud neither sleep, nor poll continuously.  Use the gpsd API to
> > wait on data available.
> >  
> 
> And in Python this looks like?

Look at the samples, like xpgs, for how some people have done it.

> My reader just does this:

It would be nice if you could share the entire code so others
could test it.

> Is there other magic out there I'm not aware of I should be using?

Many ways to skin this cat.  Look at how others have made it work:
xgps, contrib/gpsData.py, and contrib/gpsData.py are examples.

> This seems to drain the Trimble sentences continuously. Right?

No, you want the JSON TPV.

> And
> this does follow the man page guidelines AFAICT.

Yes, one way to do it.

> > > Are you saying I have to enable more strings for gpsd to give me a
> > > fix?  
> >
> > No.  Your question was how to know you had an RTK fix.  But you
> > should want more.
> >  
> 
> If I had a nickel...

Well, more like $15.

> > That is remporting in the TPV JSON.  RTFM: "man gpsd_json".
> >
> >  
> Will do. Again, is there any doc that talks about the Python API and
> how to get access to the JSON directly?

Yes.  Lots of it.  Like "man gpsd_json", plus the examples clients.
Look around the tarball, lots and lots to read.

> > But GPGGA can only report up to 12 sats in use.  You don't want to
> > be using an old GNSS receiver that uses so few sats...
> >  
> 
> The RTK thing on Trimble is proprietary, i.e. if you have RTK fix (4)
> they tell me that's that?

Uh, no.  GPGGA is bog standard NMEA.  The answer is in "man gpsd_json".

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

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