Re: [Discuss-gnuradio] linking Gnuradio and Gpredict ?

[Darren Long]

Hi Mike

Alex (the gqrx and Gpredict author) suggested using pyephem to me once when I
asked about this.  I did have a little play with it, but haven't done anything
interesting or useful.

http://rhodesmill.org/pyephem/

Darren, G0HWW

On 24/11/14 10:15, Mike Willis wrote:
> I know this is going back a bit but I would like to do the same thing for my
> Gnuradio satellite ground station. I was actually tempted to compile satellite
> tracking into a Gnuradio block. One you could simply use in a flowchart 
> without
> any of the messing about with XMLRPC but like my new hexagonal wheel project,
> with active compensatory suspension, it might be better to use what’s already 
> there.
> 
>  
> 
> Did anyone do this? And, how difficult would it be in practice to develop a
> native block that either contains predict, or accesses it? Possibly not very
> difficult at all and maybe already done?
> 
>  
> 
> Mike
> 
>  
> 
>  
> 
> --------------------------------------------------------------------------------
> 
> On 22/07/13 12:31, M Dammer wrote:
> 
>  
> 
> Is it possible to link Gnuradio and Gpredict ? I want to use Gpredict as
> 
> tracker controlling the antenna position and to pass doppler corrected
> 
> frequency data to Gnuradio.
> 
>  
> 
> In a word, yes.
> 
>  
> 
> Can be very simple. I did it by using an XML Server in the flow graph,
> 
> and wrote a quick XML client (actually I "stole" most of it from an
> 
> example), and sent the doppler info from predict via a variable.
> 
>  
> 
> doppler info was received from predict using some code to query predict
> 
> using UDP. I think I just used nc to send the UDP query to predict,
> 
> recovered the shift from the reply, and sent it back to the XML Server
> 
> running within the flow graph.
> 
>  
> 
> Unfortunately I can't find my actual code right now, but I literally
> 
> copied an example, and added the UDP Predict clients bit. It went
> 
> something like this pseudo code (Yes, this is a mix of shell,and
> 
> python, and you need to re-write the getting doppler from predict yourself, 
> but
> you get the idea, and should give you enough)
> 
>  
> 
> import time
> 
> import sys
> 
> from socket import *
> 
> import xmlrpclib
> 
> import binascii
> 
>  
> 
> s = xmlrpclib.Server("http://192.168.39.74:8081"; 
> <http://192.168.39.74:8081%22>;)
> 
> infinite=1
> 
> while infinite == 1;
> 
>   # Grab predict doppler using UDP
> 
>   DOPPLER=`nc -u -s 2 $PREDICTHOST GET_DOPPLER $NORAD_NUMBER`
> 
>   s.set_doppler_shift($DOPPLER)
> 
>   time.sleep(1)
> 
>  
> 
> The variable (lets call it doppler_shift) exists in the flowgraph,
> 
> and was multiplied appropriately and applied to the centre frequency of
> 
> a FIR filter.
> 
>  
> 
> You can pretty much pass any information you want in and out of a flow
> 
> graph using a XML Server/Client pair. I've done TX/RX switching, and
> 
> am currently working on telemetry decoding/display
> 
>  
> 
>  
> 
> Iain
> 
>  
> 
>  
> 
>  
> 
>  
> 
>  
> 
> 
> 
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