[Discuss-gnuradio] fft_vcc & file_sink

[E. Ornelas]

Hello!

I'm new to GNU Radio and USRP.

I've done this simple code below.

class topBlock(gr.top_block):
        def __init__(self):
                gr.top_block.__init__(self)

                fftsize = 256
                udecim = 256

                mywin = window.blackmanharris(fftsize)
                fft = gr.fft_vcc(fftsize, True, mywin)

                signal = usrp.source_c(0,udecim)

                ss2v = gr.stream_to_vector(gr.sizeof_gr_complex, fftsize)
                v2ss = gr.vector_to_stream(gr.sizeof_gr_complex, fftsize)

                c2f = gr.complex_to_float(fftsize)

                v_sink = gr.vector_sink_c()
                f_sink = gr.file_sink(gr.sizeof_gr_complex, "fft.data")

                self.connect(signal, ss2v, fft, v2ss, f_sink)

def main():
        print "Initilizing.."
        tb = topBlock()
        print "Flowgraph start.."
        tb.run()
        print "Exiting.."

if __name__ == "__main__":
        main()


The thing is that I don't know what kind of values is the fft giving to the
f_sink,
because if a load them on octave using "y=read_complex_binary(...)", a run
plot(abs(y(1:256))
it does come close to what I saw using the GUI version.
Without looking at the scales there should be a spike in the middle of the
graph.

http://www.nabble.com/file/p22457062/scrsht.png 

Shouldn't the first 256 values be the first fft computed from the flowgraph?

Thank you in advance!

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