1 files changed, 150 insertions, 0 deletions
diff --git a/gnuradio-examples/python/gmsk2/receive_path.py b/gnuradio-examples/python/gmsk2/receive_path.py
new file mode 100644
index 000000000..505ff7c4d
--- /dev/null
+++ b/gnuradio-examples/python/gmsk2/receive_path.py
@@ -0,0 +1,150 @@
+#!/usr/bin/env python
+#
+# Copyright 2005,2006 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 2, 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., 59 Temple Place - Suite 330,
+# Boston, MA 02111-1307, USA.
+# 
+
+from gnuradio import gr, gru, blks
+from gnuradio import usrp
+
+# from current dir
+from pick_bitrate import pick_rx_bitrate
+
+# /////////////////////////////////////////////////////////////////////////////
+#                              receive path
+# /////////////////////////////////////////////////////////////////////////////
+
+class receive_path(gr.hier_block):
+    def __init__(self, fg, demod_class, rx_subdev_spec,
+                 bitrate, decim, spb,
+                 rx_callback, options, demod_kwargs):
+
+        self.u = usrp.source_c (fusb_block_size=options.fusb_block_size,
+                                fusb_nblocks=options.fusb_nblocks)
+        adc_rate = self.u.adc_rate()
+
+        (self._bitrate, self._spb, self._decim) = \
+            pick_rx_bitrate(bitrate, demod_class.bits_per_baud(), spb, decim, adc_rate)
+
+        self.u.set_decim_rate(self._decim)
+        sw_decim = 1
+
+        if rx_subdev_spec is None:
+            rx_subdev_spec = usrp.pick_rx_subdevice(self.u)
+        self.subdev = usrp.selected_subdev(self.u, rx_subdev_spec)
+        print "Using RX d'board %s" % (self.subdev.side_and_name(),)
+
+        self.u.set_mux(usrp.determine_rx_mux_value(self.u, rx_subdev_spec))
+
+        # Create filter to get actual channel we want
+        chan_coeffs = gr.firdes.low_pass (1.0,                  # gain
+                                          sw_decim * self._spb, # sampling rate
+                                          1.0,                  # midpoint of trans. band
+                                          0.1,                  # width of trans. band
+                                          gr.firdes.WIN_HANN)   # filter type 
+
+        print "len(rx_chan_coeffs) =", len(chan_coeffs)
+
+        # Decimating Channel filter
+        # complex in and out, float taps
+        self.chan_filt = gr.fft_filter_ccc(sw_decim, chan_coeffs)
+        #self.chan_filt = gr.fir_filter_ccf(sw_decim, chan_coeffs)
+
+        # receiver
+        self.packet_receiver = \
+            blks.demod_pkts(fg,
+                            demod_class(fg, spb=self._spb, **demod_kwargs),
+                            access_code=None,
+                            callback=rx_callback,
+                            threshold=-1)
+
+        fg.connect(self.u, self.chan_filt, self.packet_receiver)
+        gr.hier_block.__init__(self, fg, None, None)
+
+        g = self.subdev.gain_range()
+        #self.set_gain((g[0] + g[1])/2)        # set gain to midpoint
+        self.set_gain(g[1])                    # set gain to max
+        self.set_auto_tr(True)                 # enable Auto Transmit/Receive switching
+
+        # Carrier Sensing Blocks
+        alpha = 0.001
+        thresh = 30   # in dB, will have to adjust
+        self.probe = gr.probe_avg_mag_sqrd_c(thresh,alpha)
+        fg.connect(self.chan_filt, self.probe)
+
+    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 up converter.
+        """
+        r = self.u.tune(0, self.subdev, target_freq)
+        if r:
+            return True
+
+        return False
+
+    def set_gain(self, gain):
+        if gain is None:
+            r = self.subdev.gain_range()
+            gain = (r[0] + r[1])/2               # set gain to midpoint
+        self.gain = gain
+        return self.subdev.set_gain(gain)
+
+    def set_auto_tr(self, enable):
+        return self.subdev.set_auto_tr(enable)
+        
+    def bitrate(self):
+        return self._bitrate
+
+    def spb(self):
+        return self._spb
+
+    def decim(self):
+        return self._decim
+
+
+    def carrier_sensed(self):
+        """
+        Return True if we think carrier is present.
+        """
+        #return self.probe.level() > X
+        return self.probe.unmuted()
+
+    def carrier_threshold(self):
+        """
+        Return current setting in dB.
+        """
+        return self.probe.threshold()
+
+    def set_carrier_threshold(self, threshold_in_db):
+        """
+        Set carrier threshold.
+
+        @param threshold_in_db: set detection threshold
+        @type threshold_in_db:  float (dB)
+        """
+        self.probe.set_threshold(threshold_in_db)
+