add rtlsdr based receiver with click & tune functionality

Call it with

 src$ ./demod/python/rtlsdr-tetra_demod_fft.py -s 1.8e6 -f 394.6e6 -g -1 -o /dev/stdout | ./float_to_bits /dev/stdin /dev/stdout | ./tetra-rx /dev/stdin

- Adjust the center frequency (-f) and gain (-g) according to your needs.
- Use left click in Full Spectrum window to roughly select a TETRA carrier.
- Use left click to fine tune the carrier by clicking on the left or right side of the spectrum.

src/demod/python/rtlsdr-tetra_demod_fft.py

@@ -0,0 +1,151 @@
+#!/usr/bin/env python
+
+# Copyright 2012 Dimitri Stolnikov <horiz0n@gmx.net>
+
+# Call it with
+# src$ ./demod/python/rtlsdr-tetra_demod_fft.py -s 1.8e6 -f 394.6e6 -g -1 -o /dev/stdout | ./float_to_bits /dev/stdin /dev/stdout | ./tetra-rx /dev/stdin
+#
+# Adjust the center frequency (-f) and gain (-g) according to your needs.
+# Use left click in Full Spectrum window to roughly select a TETRA carrier.
+# Use left click to fine tune the carrier by clicking on the left or right side of the spectrum.
+
+import sys
+import math
+from gnuradio import gr, gru, audio, eng_notation, blks2, optfir
+from gnuradio import audio
+from gnuradio.eng_option import eng_option
+from gnuradio.wxgui import fftsink2
+from grc_gnuradio import wxgui as grc_wxgui
+from optparse import OptionParser
+import osmosdr
+import wx
+
+try:
+    import cqpsk
+except:
+    from tetra_demod import cqpsk
+
+# applies frequency translation, resampling and demodulation
+
+class top_block(grc_wxgui.top_block_gui):
+  def __init__(self):
+    grc_wxgui.top_block_gui.__init__(self, title="Top Block")
+
+    options = get_options()
+
+    self.src = osmosdr.source_c()
+    self.src.set_center_freq(options.frequency)
+    self.src.set_sample_rate(int(options.sample_rate))
+
+    if options.gain is None:
+        self.src.set_gain_mode(1)
+    else:
+        self.src.set_gain_mode(0)
+        self.src.set_gain(options.gain)
+
+    # may differ from the requested rate
+    sample_rate = self.src.get_sample_rate()
+
+    symbol_rate = 18000
+    sps = 2 # output rate will be 36,000
+    new_sample_rate = symbol_rate * sps
+
+    options.low_pass = options.low_pass / 2.0
+
+    taps = gr.firdes.low_pass(1.0, sample_rate, options.low_pass, options.low_pass * 0.2, gr.firdes.WIN_HANN)
+
+    first_decim = 10
+
+    self.offset = 0
+
+    self.tuner = gr.freq_xlating_fir_filter_ccf(first_decim, taps, self.offset, sample_rate)
+
+    sys.stderr.write("sample rate: %d\n" % (sample_rate))
+
+    self.demod = cqpsk.cqpsk_demod(
+	samples_per_symbol = sps,
+        excess_bw=0.35,
+        costas_alpha=0.03,
+        gain_mu=0.05,
+        mu=0.05,
+        omega_relative_limit=0.05,
+        log=options.log,
+        verbose=options.verbose)
+
+    self.output = gr.file_sink(gr.sizeof_float, options.output_file)
+
+    rerate = float(sample_rate / float(first_decim)) / float(new_sample_rate)
+    sys.stderr.write("resampling factor: %f\n" % rerate)
+
+    #self.resamp = gr.fractional_interpolator_cc(0, rerate)
+    self.resamp = blks2.pfb_arb_resampler_ccf(1 / rerate)
+
+    self.connect(self.src, self.tuner, self.resamp, self.demod, self.output)
+
+    def fftsink2_callback(x, y):
+        sys.stderr.write("selected channel at offset: %d Hz\n" % x)
+	self.offset = -x
+        self.tuner.set_center_freq(self.offset)
+
+    self.scope = fftsink2.fft_sink_c(self.GetWin(),
+             title="Full Spectrum (click to coarse tune)",
+             fft_size=1024,
+             sample_rate=sample_rate,
+             ref_scale=2.0,
+             ref_level=-30,
+             y_divs=10,
+             fft_rate=10,
+             average=False,
+             avg_alpha=0.6)
+
+    self.Add(self.scope.win)
+    self.scope.set_callback(fftsink2_callback)
+
+    self.connect(self.src, self.scope)
+
+    def fftsink2_callback2(x, y):
+        sys.stderr.write("fine tuning channel: %d Hz\n" % x)
+	self.offset = self.offset - (x / 10)
+        self.tuner.set_center_freq(self.offset)
+
+    self.scope2 = fftsink2.fft_sink_c(self.GetWin(),
+             title="Narrow Spectrum (click to fine tune)",
+             fft_size=1024,
+             sample_rate=new_sample_rate, #sample_rate / first_decim,
+             ref_scale=2.0,
+             ref_level=-30,
+             y_divs=10,
+             fft_rate=10,
+             average=False,
+             avg_alpha=0.6)
+
+    self.Add(self.scope2.win)
+    self.scope2.set_callback(fftsink2_callback2)
+
+    self.connect(self.resamp, self.scope2)
+
+def get_options():
+    parser = OptionParser(option_class=eng_option)
+
+    parser.add_option("-s", "--sample-rate", type="eng_float", default=1800000,
+        help="set receiver sample rate (default 1800000)")
+    parser.add_option("-f", "--frequency", type="eng_float", default=394.6e9,
+        help="set receiver center frequency")
+    parser.add_option("-g", "--gain", type="eng_float", default=None,
+        help="set receiver gain")
+
+    # demodulator related settings
+    parser.add_option("-l", "--log", action="store_true", default=False, help="dump debug .dat files")
+    parser.add_option("-L", "--low-pass", type="eng_float", default=25e3, help="low pass cut-off", metavar="Hz")
+    parser.add_option("-o", "--output-file", type="string", default="out.float", help="specify the bit output file")
+    parser.add_option("-v", "--verbose", action="store_true", default=False, help="dump demodulation data")
+    (options, args) = parser.parse_args()
+    if len(args) != 0:
+        parser.print_help()
+        raise SystemExit, 1
+
+    return (options)
+
+if __name__ == '__main__':
+        tb = top_block()
+        tb.Run(True)