[Discuss-gnuradio] Questions on toy problems

[Achilleas Anastasopoulos]

Hi everybody,

I finally got my gnuradio software working (with a Fedore 2 core)
and now I have started playing with some simple examples.
I do not have a real card yet, so I mostly desgin signal processing
blocks and connect them together to experiment with the software
and do some audio stuff...

Below are a couple of questions that I have not been able to resolve.

Thanks
Achilleas

1) What is the difference between building a graph containing, say,
a transmitter and a receiver block (connected together) and then
running the whole graph,
versus
writting two separate programs, one for Tx and one for Rx and
connecting them through a unix pipe, eg, tx | rx.
I thought I saw somewhere in the documentation that this is doable too.

Is there an advantage of one versus the other method?


2) How can I ensure that a signal generator does not run forever, but 
only for a specified time and/or number of samples?

And finally,
3) I am trying to build a toy application where I open 2
fft windows to watch tow differnt signals in the same graph.
I tried 2 versions and neither works as expected. Any
suggestions? (I am a really newby to python...)

Version A
=====================================
#!/usr/bin/env python

from gnuradio import gr
from gnuradio.wxgui import stdgui
from gnuradio.wxgui import fftsink
import wx

class test_app_flow_graph (stdgui.gui_flow_graph):
    def __init__(self, frame, panel, vbox, argv):
        stdgui.gui_flow_graph.__init__ (self, frame, panel, vbox, argv)

        input_rate = 8.00e3
        f1 = 1.00e3
        f2 = 1.00e3
        src1 = gr.sig_source_c (input_rate, gr.GR_SIN_WAVE, f1, 10e3)
        src2 = gr.sig_source_c (input_rate, gr.GR_SIN_WAVE, f2, 10e3)
        block1, fft_win1 = fftsink.make_fft_sink_c (self, panel, 
"FFT1", 128,
input_rate)
        block2, fft_win2 = fftsink.make_fft_sink_c (self, panel, 
"FFT2", 128,
input_rate)
        self.connect (src1, block1)
        self.connect (src2, block2)
        vbox.Add (fft_win1, 1, wx.EXPAND)
        vbox.Add (fft_win2, 1, wx.EXPAND)

def main ():
    app = stdgui.stdapp (test_app_flow_graph, "FFT Sink Test App")
    app.MainLoop ()

if __name__ == '__main__':
    main ()
========================================


Version B
=====================================
#!/usr/bin/env python

from gnuradio import gr
from gnuradio.wxgui import stdgui
from gnuradio.wxgui import fftsink
import wx

class test_app_flow_graph (stdgui.gui_flow_graph):
    def __init__(self, frame, panel, vbox, argv):
        stdgui.gui_flow_graph.__init__ (self, frame, panel, vbox, argv)

        input_rate = 8.00e3
        f = 1.00e3

        src = gr.sig_source_c (input_rate, gr.GR_SIN_WAVE, f, 10e3)
        block, fft_win = fftsink.make_fft_sink_c (self, panel, "FFT1", 128,
input_rate)
        self.connect (src, block)
        vbox.Add (fft_win, 1, wx.EXPAND)

def main ():
    app1 = stdgui.stdapp (test_app_flow_graph, "FFT1 Sink Test App")
    app2 = stdgui.stdapp (test_app_flow_graph, "FFT2 Sink Test App")
    app1.MainLoop ()
    app2.MainLoop ()

if __name__ == '__main__':
    main ()