Re: [Discuss-gnuradio] Continuos data transmission using messages ...

[Eric Blossom]

On Tue, Feb 26, 2008 at 12:02:31PM -0500, Kshitij Kumar Singh wrote:
> 
> 
> > I think you are misunderstanding how gr.message_sink works.  Since
> > it's possible to set the item size small (e.g., gr.sizeof_float), it
> > returns as many samples as it can in a message.  It does however
> > provide you information about what it did in the arg1 and arg2 field.
> > 
> >   // build a message to hold whatever we've got
> >   gr_message_sptr msg = gr_make_message(0,          // msg type
> >                                     d_itemsize,     // arg1 for other end
> >                                     noutput_items,  // arg2 for other end 
> > (redundant)
> >                                     noutput_items * d_itemsize);   // len 
> > of msg
> > 
> > Eric
> Eric, thanks for the reply and for clearing up the confusion. I now
> understand how this works. Sorry if I did not phrase my question
> correctly earlier: I want to transmit a file using packets repeatedly,
> i.e. the first packet transmits the entire contents of file(as a string,
> size <= 4096), the second packet again transmits the entire file and so
> on. I thought that the best place to start was tx_voice.py since all I
> needed to do was replace the audio_rx class with my own which got the
> data from a file. The program ran perfectly without glitches but after
> the sending the first packet, I was unable to loop around for a second
> time (Still can't figure it out). So I decided to start from scratch and
> got confused with the message stuff.
> 
> Thanks for your patience.
> 
> Regards,
> Kshitij

Take a look at the code in gnuradio-examples/python/digital.  See
especially benchmark_tx.py, benchmark_rx.py and tunnel.py

Eric