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