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[Discuss-gnuradio] Question on output of FFT block
From: |
Brook Lin |
Subject: |
[Discuss-gnuradio] Question on output of FFT block |
Date: |
Mon, 10 Mar 2008 11:07:48 -0700 (PDT) |
Hi All,
I am not familiar with Python. I got confused on the output of FFT block. I
can record the raw data coming to the USRP. However, I also need the data
coming outof FFT block. For example, when usrp_fft.py is running, it calls
fftsink2.py and give the spectrum plot. I found that in class fft_window in
fftsink2.py file, def set_data() gives the data after FFT block, which is
points[:,1]. Am I right? How can I show the maximum value of points[:,1] in
status bar of FFT_GUI window?
If I change the def set_data() which I attached below, I can print that max
value in the terminal, but I can not update the frequency from GUI window.
Can I do both things, updating freq and updating the max(points[:,1]) value
in GUI status bar not the terminal?
I also tried adding a vector sink in class fft_sink_c,
self.connect(self, self.s2p, self.one_in_n, self.fft, self.c2mag, self.avg,
self.log, self.sink)
self.win = fft_window(self, parent, size=size)
self.set_average(self.average)
self.dst2 = gr.vector_sink_f ()
self.connect(self.log, self.dst2)
However, it doesn't work.
I was stcuk here for a long time. If anyone can help me with this question,
I really appreciate!
Brook
##############
def set_data (self, evt):
dB = evt.data
L = len (dB)
if self.peak_hold:
if self.peak_vals is None:
self.peak_vals = dB
else:
self.peak_vals = numpy.maximum(dB, self.peak_vals)
dB = self.peak_vals
x = max(abs(self.fftsink.sample_rate),
abs(self.fftsink.baseband_freq))
#if x >= 1e9:
# sf = 1e-9
# units = "GHz"
if x >= 1e6: #elif
sf = 1e-6
units = "MHz"
else:
sf = 1e-3
units = "kHz"
if self.fftsink.input_is_real: # only plot 1/2 the points
x_vals = ((numpy.arange (L/2)
* (self.fftsink.sample_rate * sf / L))
+ self.fftsink.baseband_freq * sf)
points = numpy.zeros((len(x_vals), 2), numpy.float64)
points[:,0] = x_vals
points[:,1] = dB[0:L/2]
else:
# the "negative freqs" are in the second half of the array
x_vals = ((numpy.arange (-L/2, L/2)
* (self.fftsink.sample_rate * sf / L))
+ self.fftsink.baseband_freq * sf)
points = numpy.zeros((len(x_vals), 2), numpy.float64)
points[:,0] = x_vals
points[:,1] = numpy.concatenate ((dB[L/2:], dB[0:L/2]))
lines = plot.PolyLine (points, colour='BLUE')
graphics = plot.PlotGraphics ([lines],
title=self.fftsink.title,
xLabel = units, yLabel = "dB")
self.Draw (graphics, xAxis=None, yAxis=self.y_range)
self.update_y_range ()
allpoints=[]
allpoints=points[:,1]
#print 'x_vals',x_vals, len(x_vals)
print 'points',allpoints, len(allpoints)
print 'max_point',max(allpoints)
mag_max=0
for idx in range(len(allpoints)):
if allpoints[idx]>mag_max:
mag_max = allpoints[idx]
idx_mag_max = idx
print 'mag_max is ', mag_max
print 'ndx_mag_max is ', idx_mag_max
deltafreq = (2e6)*(256*(512**(-1)))
if mag_max>10:
print 'There is a signal @ delta',deltafreq/1e6, 'MHz'
###########################
--
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