#!/usr/bin/env python
#
# Copyright 2006,2007,2011,2012 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 this program; if not, write to the Free Software Foundation, Inc.,
# 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
#
"""
Here is a bit of code that will receive SCA analog subcarriers of FM
Broadcast Stations using the USRP. It is a modified version of
usrp_wfm_rcv.py.
Common SCA frequencies are 67 kHz and 92 kHz. SCA is used for Reading
Services for the Blind, Background Music, Foreign Language Services, and
other services. Remember you may hear static when tuned to a FM station
because this code only outputs SCA audio.
The USRP gain is critical for good decoding. Adjust for minimum noise.
I use the Post FM Demod FFT to check for SCA subcarriers and to adjust
the USRP gain for the lowest noise floor. The stereo pilot at 19 KHz,
the stereo difference signal around 38 KHz, and RDS at 57 KHz are also
displayed on the Post FM Demod FFT if present.
The range below 67 kHz is used for SCA only when Stereo is not used.
The SCA recieve range is not as far as the main FM carrier receive range
so tune in strong local stations first.
I tried to comment the code with the various parameters. There seems to
be several choices for a couple of them. I coded the common ones I see
here.
In the local area there are a couple of stations using digital SCA.
These look similar to narrow DRM signals and I wonder if they are using
OFDM.
"""
from gnuradio import gr, audio, uhd
from gnuradio import blocks
from gnuradio import filter
from gnuradio import analog
from gnuradio.eng_option import eng_option
from gnuradio.wxgui import slider, powermate
from gnuradio.wxgui import stdgui2, fftsink2, form
from optparse import OptionParser
import sys
import math
import wx
class wfm_rx_sca_block (stdgui2.std_top_block):
def __init__(self,frame,panel,vbox,argv):
stdgui2.std_top_block.__init__ (self,frame,panel,vbox,argv)
parser=OptionParser(option_class=eng_option)
parser.add_option("-a", "--args", type="string", default="",
help="UHD device address args [default=%default]")
parser.add_option("", "--spec", type="string", default=None,
help="Subdevice of UHD device where appropriate")
parser.add_option("-A", "--antenna", type="string", default=None,
help="select Rx Antenna where appropriate")
parser.add_option("-f", "--freq", type="eng_float", 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("-V", "--volume", type="eng_float", default=None,
help="set volume (default is midpoint)")
parser.add_option("-O", "--audio-output", type="string", default="default",
help="pcm device name. E.g., hw:0,0 or surround51 or /dev/dsp")
parser.add_option("", "--freq-min", type="eng_float", default=87.9e6,
help="Set a minimum frequency [default=%default]")
parser.add_option("", "--freq-max", type="eng_float", default=108.1e6,
help="Set a maximum frequency [default=%default]")
(options, args) = parser.parse_args()
if len(args) != 0:
parser.print_help()
sys.exit(1)
self.frame = frame
self.panel = panel
self.vol = 0
self.state = "FREQ"
self.freq = 0
self.fm_freq_min = options.freq_min
self.fm_freq_max = options.freq_max
# build graph
self.u = uhd.usrp_source(device_addr=options.args, stream_args=uhd.stream_args('fc32'))
# Set the subdevice spec
if(options.spec):
self.u.set_subdev_spec(options.spec, 0)
# Set the antenna
if(options.antenna):
self.u.set_antenna(options.antenna, 0)
usrp_rate = 320e3
demod_rate = 320e3
audio_rate = 32e3
sca_demod_rate = 64e3
audio_decim = int(demod_rate / audio_rate)
sca_chanfilt_decim = int(demod_rate / sca_demod_rate)
self.u.set_samp_rate(usrp_rate)
dev_rate = self.u.get_samp_rate()
nfilts = 32
chan_coeffs = filter.optfir.low_pass(nfilts, # gain
nfilts*usrp_rate, # sampling rate
100e3, # passband cutoff
140e3, # stopband cutoff
0.1, # passband ripple
60) # stopband attenuation
rrate = usrp_rate / dev_rate
self.chan_filt = filter.pfb.arb_resampler_ccf(rrate, chan_coeffs, nfilts)
#Create demodulator block for Main FM Channel
max_dev = 75e3
fm_demod_gain = demod_rate/(2*math.pi*max_dev)
self.fm_demod = analog.quadrature_demod_cf(fm_demod_gain)
# Note - deemphasis is not applied to the Main FM Channel as
# main audio is not decoded
# SCA Devation is 10% of carrier but some references say 20%
# if mono with one SCA (6 KHz seems typical)
max_sca_dev = 6e3
# Create filter to get SCA channel we want
sca_chan_coeffs = filter.firdes.low_pass(1.0, # gain
demod_rate, # sampling rate
max_sca_dev, # cutoff freq
max_sca_dev/3, # trans. band
filter.firdes.WIN_HANN) # filter type
self.ddc = filter.freq_xlating_fir_filter_fcf(sca_chanfilt_decim, # decim rate
sca_chan_coeffs, # taps
0, # freq translation amount (Gets set by the UI)
demod_rate) # input sample rate
#Create demodulator block for SCA Channel
sca_demod_gain = sca_demod_rate/(2*math.pi*max_sca_dev)
self.fm_demod_sca = analog.quadrature_demod_cf(sca_demod_gain)
# SCA analog audio is bandwidth limited to 5 KHz
max_sca_audio_freq = 5.0e3
# SCA analog deephasis is 150 uS (75 uS may be used)
sca_tau = 150e-6
# compute FIR filter taps for SCA audio filter
audio_coeffs = filter.firdes.low_pass(1.0, # gain
sca_demod_rate, # sampling rate
max_sca_audio_freq, # cutoff freq
max_sca_audio_freq/2.5, # trans. band
filter.firdes.WIN_HAMMING)
# input: float; output: float
self.audio_filter = filter.fir_filter_fff(audio_decim, audio_coeffs)
# Create deemphasis block that is applied after SCA demodulation
self.deemph = analog.fm_deemph(audio_rate, sca_tau)
self.volume_control = blocks.multiply_const_ff(self.vol)
# sound card as final sink
self.audio_sink = audio.sink(int (audio_rate),
options.audio_output,
False) # ok_to_block
# now wire it all together
self.connect(self.u, self.chan_filt, self.fm_demod,
self.ddc, self.fm_demod_sca)
self.connect(self.fm_demod_sca, self.audio_filter,
self.deemph, self.volume_control,
self.audio_sink)
self._build_gui(vbox, usrp_rate, demod_rate, sca_demod_rate, audio_rate)
if options.gain is None:
# if no gain was specified, use the mid-point in dB
g = self.u.get_gain_range()
options.gain = float(g.start()+g.stop())/2
if options.volume is None:
g = self.volume_range()
options.volume = float(g[0]+g[1])/2
frange = self.u.get_freq_range()
if(frange.start() > self.fm_freq_max or frange.stop() < self.fm_freq_min):
sys.stderr.write("Radio does not support required frequency range.\n")
sys.exit(1)
if(options.freq < self.fm_freq_min or options.freq > self.fm_freq_max):
sys.stderr.write("Requested frequency is outside of required frequency range.\n")
sys.exit(1)
# set initial values
self.set_gain(options.gain)
self.set_vol(options.volume)
if not(self.set_freq(options.freq)):
self._set_status_msg("Failed to set initial frequency")
self.set_sca_freq(67000) # A common SCA Frequency
def _set_status_msg(self, msg, which=0):
self.frame.GetStatusBar().SetStatusText(msg, which)
def _build_gui(self, vbox, usrp_rate, demod_rate, sca_demod_rate, audio_rate):
def _form_set_freq(kv):
return self.set_freq(kv['freq'])
def _form_set_sca_freq(kv):
return self.set_sca_freq(kv['sca_freq'])
if 1:
self.src_fft = fftsink2.fft_sink_c(self.panel, title="Data from USRP",
fft_size=512, sample_rate=usrp_rate,
ref_scale=32768.0, ref_level=0, y_divs=12)
self.connect (self.u, self.src_fft)
vbox.Add (self.src_fft.win, 4, wx.EXPAND)
if 1:
post_demod_fft = fftsink2.fft_sink_f(self.panel, title="Post FM Demod",
fft_size=2048, sample_rate=demod_rate,
y_per_div=10, ref_level=0)
self.connect (self.fm_demod, post_demod_fft)
vbox.Add (post_demod_fft.win, 4, wx.EXPAND)
if 0:
post_demod_sca_fft = fftsink2.fft_sink_f(self.panel, title="Post SCA Demod",
fft_size=1024, sample_rate=sca_demod_rate,
y_per_div=10, ref_level=0)
self.connect (self.fm_demod_sca, post_demod_sca_fft)
vbox.Add (post_demod_sca_fft.win, 4, wx.EXPAND)
if 0:
post_deemph_fft = fftsink2.fft_sink_f (self.panel, title="Post SCA Deemph",
fft_size=512, sample_rate=audio_rate,
y_per_div=10, ref_level=-20)
self.connect (self.deemph, post_deemph_fft)
vbox.Add (post_deemph_fft.win, 4, wx.EXPAND)
# control area form at bottom
self.myform = myform = form.form()
hbox = wx.BoxSizer(wx.HORIZONTAL)
hbox.Add((5,0), 0)
myform['freq'] = form.float_field(
parent=self.panel, sizer=hbox, label="Freq", weight=1,
callback=myform.check_input_and_call(_form_set_freq, self._set_status_msg))
hbox.Add((5,0), 0)
myform['freq_slider'] = \
form.quantized_slider_field(parent=self.panel, sizer=hbox, weight=3,
range=(self.fm_freq_min, self.fm_freq_max, 0.1e6),
callback=self.set_freq)
hbox.Add((5,0), 0)
vbox.Add(hbox, 0, wx.EXPAND)
hbox = wx.BoxSizer(wx.HORIZONTAL)
hbox.Add((5,0), 0)
myform['sca_freq'] = form.float_field(
parent=self.panel, sizer=hbox, label="SCA", weight=1,
callback=myform.check_input_and_call(_form_set_sca_freq, self._set_status_msg))
hbox.Add((5,0), 0)
myform['sca_freq_slider'] = \
form.quantized_slider_field(parent=self.panel, sizer=hbox, weight=3,
range=(38e3, 100e3, 1.0e3),
callback=self.set_sca_freq)
hbox.Add((5,0), 0)
vbox.Add(hbox, 0, wx.EXPAND)
hbox = wx.BoxSizer(wx.HORIZONTAL)
hbox.Add((5,0), 0)
myform['volume'] = \
form.quantized_slider_field(parent=self.panel, sizer=hbox, label="Volume",
weight=3, range=self.volume_range(),
callback=self.set_vol)
hbox.Add((5,0), 1)
g = self.u.get_gain_range()
myform['gain'] = \
form.quantized_slider_field(parent=self.panel, sizer=hbox, label="Gain",
weight=3, range=(g.start(), g.stop(), g.step()),
callback=self.set_gain)
hbox.Add((5,0), 0)
vbox.Add(hbox, 0, wx.EXPAND)
try:
self.knob = powermate.powermate(self.frame)
self.rot = 0
powermate.EVT_POWERMATE_ROTATE (self.frame, self.on_rotate)
powermate.EVT_POWERMATE_BUTTON (self.frame, self.on_button)
except:
print "FYI: No Powermate or Contour Knob found"
def on_rotate (self, event):
self.rot += event.delta
if (self.state == "FREQ"):
if self.rot >= 3:
self.set_freq(self.freq + .1e6)
self.rot -= 3
elif self.rot <=-3:
self.set_freq(self.freq - .1e6)
self.rot += 3
else:
step = self.volume_range()[2]
if self.rot >= 3:
self.set_vol(self.vol + step)
self.rot -= 3
elif self.rot <=-3:
self.set_vol(self.vol - step)
self.rot += 3
def on_button (self, event):
if event.value == 0: # button up
return
self.rot = 0
if self.state == "FREQ":
self.state = "VOL"
else:
self.state = "FREQ"
self.update_status_bar ()
def set_vol (self, vol):
g = self.volume_range()
self.vol = max(g[0], min(g[1], vol))
self.volume_control.set_k(10**(self.vol/10))
self.myform['volume'].set_value(self.vol)
self.update_status_bar ()
def set_freq(self, target_freq):
"""
Set the center frequency we're interested in.
Args:
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.set_center_freq(target_freq)
if r:
self.freq = target_freq
self.myform['freq'].set_value(target_freq) # update displayed value
self.myform['freq_slider'].set_value(target_freq) # update displayed value
self.update_status_bar()
self._set_status_msg("OK", 0)
return True
self._set_status_msg("Failed", 0)
return False
def set_sca_freq(self, target_sca_freq):
self.ddc.set_center_freq(-target_sca_freq)
self.myform['sca_freq'].set_value(target_sca_freq) # update displayed value
self.myform['sca_freq_slider'].set_value(target_sca_freq) # update displayed value
self.update_status_bar()
self._set_status_msg("OK", 0)
return True
def set_gain(self, gain):
self.myform['gain'].set_value(gain) # update displayed value
self.u.set_gain(gain)
def update_status_bar (self):
msg = "Volume:%r Setting:%s" % (self.vol, self.state)
self._set_status_msg(msg, 1)
self.src_fft.set_baseband_freq(self.freq)
def volume_range(self):
return (-20.0, 0.0, 0.5)
if __name__ == '__main__':
app = stdgui2.stdapp (wfm_rx_sca_block, "USRP WFM SCA RX")
app.MainLoop ()