2 TVRx Boards on 1 USRP

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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