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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