Hello All,
I am trying to receive only a small portion of different FM station
frequencies stored in a string. To do this I modified the
usrp_wfm_rcv_nogui.py. The way I am doing this is to feed the incoming
stream from usrp.source_c() to vector of a fixed length and then listen
to
that vector. My problem is when I try to sink the vector into the audio
sink
all I hear is noise. But when I use usrp.source_c() directly it plays
fine
but ofcourse I end up listening to a continuous transmission instead of
a
short segment. The following is the code (modified version of
usrp_wfm_rcv_nogui.py. I hope i made my issue clear enough. PLease ask
me if
you need any clarification. I really need help at this point. Thank you.
#!/usr/bin/env python
Copyright 2005,2006,2007 Free Software Foundation, Inc.
This file is part of GNU Radio
GNU Radio is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 3, or (at your option)
any later version.
GNU Radio is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with GNU Radio; see the file COPYING. If not, write to
the Free Software Foundation, Inc., 51 Franklin Street,
Boston, MA 02110-1301, USA.
from gnuradio import gr, gru, eng_notation, optfir
from gnuradio import audio
from gnuradio import usrp
from gnuradio import blks2
from gnuradio.eng_option import eng_option
from optparse import OptionParser
from usrpm import usrp_dbid
import sys
import math,time,re
def pick_subdevice(u):
“”"
The user didn’t specify a subdevice on the command line.
Try for one of these, in order: TV_RX, BASIC_RX, whatever is on side
A.
@return a subdev_spec
"""
return usrp.pick_subdev(u, (usrp_dbid.TV_RX,
usrp_dbid.TV_RX_REV_2,
usrp_dbid.TV_RX_REV_3,
usrp_dbid.BASIC_RX))
class wfm_rx_block (gr.top_block):
def __init__(self):
gr.top_block.__init__(self)
parser=OptionParser(option_class=eng_option)
parser.add_option("-R", "--rx-subdev-spec", type="subdev",
default=None,
help=“select USRP Rx side A or B (default=A)”)
parser.add_option(“-f”, “–freq”, type=“str”, default=100.1e6,
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(“-O”, “–audio-output”, type=“string”,
default=“”,
help=“pcm device name. E.g., hw:0,0 or
surround51
or /dev/dsp”)
(options, args) = parser.parse_args()
if len(args) != 0:
parser.print_help()
sys.exit(1)
self.vol = 3
self.state = "FREQ"
self.freq = 0
# build graph
self.u = usrp.source_c() # usrp is data
source
adc_rate = self.u.adc_rate() # 64 MS/s
usrp_decim = 200
self.u.set_decim_rate(usrp_decim)
usrp_rate = adc_rate / usrp_decim # 320 kS/s
chanfilt_decim = 1
demod_rate = usrp_rate / chanfilt_decim
audio_decimation = 10
audio_rate = demod_rate / audio_decimation # 32 kHz
if options.rx_subdev_spec is None:
options.rx_subdev_spec = pick_subdevice(self.u)
self.u.set_mux(usrp.determine_rx_mux_value(self.u,
options.rx_subdev_spec))
self.subdev = usrp.selected_subdev(self.u,
options.rx_subdev_spec)
print “Using RX d’board %s” % (self.subdev.side_and_name(),)
chan_filt_coeffs = optfir.low_pass (1, # gain
usrp_rate, # sampling rate
80e3, # passband
cutoff
115e3, # stopband
cutoff
0.1, # passband
ripple
60) # stopband
attenuation
#print len(chan_filt_coeffs)
chan_filt = gr.fir_filter_ccf (chanfilt_decim, chan_filt_coeffs)
self.guts = blks2.wfm_rcv (demod_rate, audio_decimation)
self.volume_control = gr.multiply_const_ff(self.vol)
# sound card as final sink
audio_sink = audio.sink(int(audio_rate),
options.audio_output,
False) # ok_to_block
# now wire it all together
src=self.u
c2f_vec = gr.stream_to_vector(gr.sizeof_gr_complex,1)
snk_vec = gr.vector_sink_c()
self.connect(src,snk_vec)
self.run()
vec_data = snk_vec.data()
self.disconnect_all()
if options.gain is None:
# if no gain was specified, use the mid-point in dB
g = self.subdev.gain_range()
options.gain = float(g[0]+g[1])/2
# set initial values
self.set_gain(options.gain)
Y=options.freq
c_freqs_temp=re.findall(r"(-\d+.\d+|\d+.\d+|\d+)",Y)
c_freqs=[]
for ndx0 in range(len(c_freqs_temp)):
c_freqs_temp_1=float(c_freqs_temp[ndx0])
c_freqs.append(c_freqs_temp_1)
print c_freqs,len(c_freqs)
for ndx1 in range(0,1):
self.set_freq(c_freqs[ndx1])
vec_src=gr.vector_source_c(vec_data,False)
self.connect (vec_src, self.guts, self.volume_control, audio_sink)
def set_vol (self, vol):
self.vol = vol
self.volume_control.set_k(self.vol)
self.update_status_bar ()
def set_freq(self, target_freq):
"""
Set the center frequency we're interested in.
@param target_freq: frequency in Hz
@rypte: bool
Tuning is a two step process. First we ask the front-end to
tune as close to the desired frequency as it can. Then we use
the result of that operation and our target_frequency to
determine the value for the digital down converter.
"""
r = self.u.tune(0, self.subdev, target_freq)
if r:
self.freq = target_freq
self.update_status_bar()
self._set_status_msg("OK", 0)
return True
self._set_status_msg("Failed", 0)
return False
def set_gain(self, gain):
self.subdev.set_gain(gain)
def update_status_bar (self):
msg = "Freq: %s Volume:%f Setting:%s" % (
eng_notation.num_to_str(self.freq), self.vol, self.state)
self._set_status_msg(msg, 1)
def _set_status_msg(self, msg, which=0):
print msg
if name == ‘main’:
tb = wfm_rx_block()
try:
tb.run()
except KeyboardInterrupt:
pass
–
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