For anyone with a similar predicament, the sillyness lies in tuning the
second tuner to the incorrect channel.
Fix this and you'll be on your way.
Aadil
>
>
> Hi,
>
> I am trying to use 1 USRP with two TVRx daughter boards to capture
> Separate
> FM signals and write them to file.
>
> I get a noisy signal. I hope someone can tell me what i've done wrong. I
> can't see the error.
>
> I have included the code that i'm using. it's built from the
> usrp_rx_cfile.py
>
> ---------------------------------------------------------------------------------------------------
>
> class my_graph(gr.flow_graph):
>
> def __init__(self):
> gr.flow_graph.__init__(self)
>
> usage="%prog: [options] output_filename0 output_filename1 "
> parser = OptionParser(option_class=eng_option, usage=usage)
> parser.add_option("-R", "--rx-subdev-spec0", type="subdev",
> default=None,
> help="first channel select USRP Rx side A or B
> (default=A)")
> parser.add_option("-r", "--rx-subdev-spec1", type="subdev",
> default=None,
> help="second channel select USRP Rx side A or B
> (default=A)")
> parser.add_option("-d", "--decim", type="int", default=128,
> help="set fgpa decimation rate to DECIM
> [default=%default]")
> parser.add_option("-f", "--freq", type="eng_float", default=89e6,
> help="set frequency to FREQ", metavar="FREQ")
> parser.add_option("-g", "--gain", type="eng_float", default=None,
> help="set gain in dB (default is midpoint)")
> parser.add_option("-N", "--nsamples", type="eng_float",
> default=9600000,
> help="number of samples to collect
> [default=9600000]")
> parser.add_option("-t", "--time", type="eng_float", default=0,
> help="length of recording in seconds [default=0]")
>
> (options, args) = parser.parse_args ()
> if len(args) != 2:
> parser.print_help()
> raise SystemExit, 1
>
> filename0 = args[0]
> filename1 = args[1]
>
> decim_rate = options.decim
>
> if options.time:
> options.nsamples = int(float(options.time) * 64e6 /
> float(decim_rate))
> else:
> options.time = float(options.nsamples / (64e6 /
> float(decim_rate)) )
>
> if options.freq is None:
> parser.print_help()
> sys.stderr.write('You must specify the frequency with -f
> FREQ\n');
> raise SystemExit, 1
>
> # build the graph
>
> self.u = usrp.source_c(decim_rate = options.decim, nchan = 2)
>
> self.head0 = gr.head(gr.sizeof_gr_complex, int(options.nsamples ))
> self.head1 = gr.head(gr.sizeof_gr_complex, int(options.nsamples ))
>
> # deinterleave two channels from FPGA
> self.di = gr.deinterleave(gr.sizeof_gr_complex)
>
> self.dst0 = gr.file_sink(gr.sizeof_gr_complex, filename0)
> self.dst1 = gr.file_sink(gr.sizeof_gr_complex, filename1)
>
> # wire up the head of the chain
> self.connect(self.u, self.di)
>
> self.connect((self.di,0), self.head0, self.dst0)
> self.connect((self.di,1), self.head1, self.dst1)
>
> if options.rx_subdev_spec0 is None:
> options.rx_subdev_spec0 = (0,0)
> if options.rx_subdev_spec1 is None:
> options.rx_subdev_spec1 = (1,0)
>
> mux_val0 = usrp.determine_rx_mux_value(self.u,
> options.rx_subdev_spec0)
> mux_val1 = usrp.determine_rx_mux_value(self.u,
> options.rx_subdev_spec1)
>
> mux_val0 |= (mux_val1 << 8) & 0xff00
>
> self.u.set_mux(mux_val0)
>
> # determine the daughterboard subdevice we're using
> self.subdev0 = usrp.selected_subdev(self.u,
> options.rx_subdev_spec0)
> print "Using RX d'board %s" % (self.subdev0.side_and_name(),)
> self.subdev1 = usrp.selected_subdev(self.u,
> options.rx_subdev_spec1)
> print "Using RX d'board %s" % (self.subdev1.side_and_name(),)
>
> input_rate = self.u.adc_freq() / self.u.decim_rate()
> print "USB sample rate: %s" %
> (eng_notation.num_to_str(input_rate))
>
> print "Freq is set to: %s" % (eng_notation.num_to_str(options.freq
> ))
>
> print "Recording time is: %ss" % (options.time)
>
> print "Mux value is: %x" % (mux_val0 & 65535)
>
> if options.gain is None:
> # if no gain was specified, use the mid-point in dB
> g0 = self.subdev0.gain_range()
> g1 = self.subdev1.gain_range()
> options.gain = float(g0[0]+g0[1])/2
>
>
> self.subdev0.set_gain(options.gain)
> self.subdev1.set_gain(options.gain)
>
> r0 = self.u.tune(0, self.subdev0, options.freq)
> r1 = self.u.tune(0, self.subdev1, options.freq)
>
> if not r0:
> sys.stderr.write('Failed to set frequency\n')
> raise SystemExit, 1
>
> if not r1:
> sys.stderr.write('Failed to set frequency\n')
> raise SystemExit, 1
>
>
> if __name__ == '__main__':
> try:
> my_graph().run()
> except KeyboardInterrupt:
> pass
>
> ------------------------------------------------------------------------------------------------------
>
>
> thanks,
>
> Aadil
>
>
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