Re: Getting GPS data into stream

[Fabian Schwartau]

Doing it the way Marcus M. described wasn actually not that complicated 
as I expected. I have a small "Embedded Python Block" that does more or 
less what I need. The file is attached, if anyone else needs this :)
The error handling is a bit rough and there are probably many things to 
improve on, but its a starting point.

Am 07.05.23 um 13:09 schrieb Fabian Schwartau:
> Hi again,
> as I described earlier, I am now using a "Tags Strobe" block to 
> periodically tag the data with the current gps coordinates. Within the 
> "Tag Strobes" I use a function call to create the value:
> pmt.to_pmt(gps.get_current_gps_position())
> And this function is defined in a "Python Module" block.
> But it seems that the function is only called once at startup and then 
> never again. Which is quite useless in my case. Is that correct? Is 
> there any other easy way to get the gps data into a stream as tags 
> within GRC? I am not familiar with programming my own blocks and I don't 
> see myself capable of doing what Marcus M. suggested earier, without 
> spending a considerable amount of time.
>
> Best,
> Fabian
>
> Am 05.05.23 um 09:58 schrieb Marcus Müller:
> > Hi Fabian,
> > it's interleaved real, imag, real, imag. If you used 
> > dtype=np.complex64 instead of float32 (and then not double the count), 
> > you'd get it interpreted exactly that way :)
> >
> > Cheers,
> > Marcus
> >
> > On 04.05.23 19:38, Fabian Schwartau wrote:
> > > Sorry again, never mind... I found the problem.
> > > The source code for reading the data does not include the fact that I 
> > > am reading complex data and also three streams. Change the one line to:
> > > data=np.fromfile(file=fh, dtype=np.float32, 
> > > count=3*2*int(header_info['nitems']), sep='', offset=0)
> > > and everything seems to work as expected. Now I just have to figure 
> > > out how the data is ordered in that blob ;)
> > >
> > > Best,
> > > Fabian
> > >
> > > Am 04.05.23 um 19:19 schrieb Fabian Schwartau:
> > > > Hi everyone,
> > > >
> > > > I think I got hit by https://github.com/gnuradio/gnuradio/issues/5568.
> > > > Exactly the same error message. Is there any update on that issue or 
> > > > a workaround?
> > > > Attached are my files.
> > > >
> > > > Best,
> > > > Fabian
> > > >
> > > > Am 03.05.23 um 21:01 schrieb Marcus D. Leech:
> > > > > On 03/05/2023 14:59, Fabian Schwartau wrote:
> > > > > > Sorry, forget it. Wrong sink...
> > > > > You probably want:
> > > > >
> > > > > https://wiki.gnuradio.org/index.php/File_Meta_Sink
> > > > > > Am 03.05.23 um 20:52 schrieb Fabian Schwartau:
> > > > > > > OK, I think I found an easier way (at least for me), without 
> > > > > > > having to write my own module - never done that.
> > > > > > > I used the "Tags Strobe" block in combination with the "Python 
> > > > > > > Module" for my gps_get_position() function.
> > > > > > > Anyway, where can I find a definition of the format of the 
> > > > > > > "Tagged File Sink"? I need to read this with antoher program, 
> > > > > > > without gnuradio, but in python.
> > > > > > >
> > > > > > > Best,
> > > > > > > Fabian
> > > > > > >
> > > > > > > Am 03.05.23 um 20:04 schrieb Marcus Müller:
> > > > > > > > Hi Fabian,
> > > > > > > >
> > > > > > > > I'd write a block that copies a stream in- to output. It might 
> > > > > > > > query gpsd every time the work() function is called, or have a 
> > > > > > > > FIFO into which data from gspd is being pushed by a separate 
> > > > > > > > thread (or by reading from a socket or however gspd works, I 
> > > > > > > > must admit I'm not sure).
> > > > > > > >
> > > > > > > > You then take that info, and encode the long, lat, uncertainty 
> > > > > > > > as (double, double, double) PMT tuple. You then use add_item_tag 
> > > > > > > > to add that PMT to the first sample in your output buffer.
> > > > > > > >
> > > > > > > > You'd feed the result into a metadata file sink block: That 
> > > > > > > > saves things in a serialized format ready for retrieval.
> > > > > > > >
> > > > > > > > Best,
> > > > > > > > Marcus
> > > > > > > >
> > > > > > > > On 5/3/23 19:52, Fabian Schwartau wrote:
> > > > > > > > > Hi everyone,
> > > > > > > > >
> > > > > > > > > I am trying to record some data from an SDR and would like to 
> > > > > > > > > sync/tag the data with the current gps position from gpsd. I am 
> > > > > > > > > kind of stuck and don't know how a possible solution for that 
> > > > > > > > > might look like in grc.
> > > > > > > > > I have a python function that gets the current position as a 
> > > > > > > > > tuple, but how do I get this into my data stream, which I would 
> > > > > > > > > like to write to a CSV file or similar?
> > > > > > > > > I am not asking for a solution of my problem, just point me in 
> > > > > > > > > the right direction ;)
> > > > > > > > >
> > > > > > > > > Best,
> > > > > > > > > Fabian

gpstagger.py
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