1 files changed, 57 insertions, 0 deletions
diff --git a/gr-pager/src/flex_demod.py b/gr-pager/src/flex_demod.py
new file mode 100644
index 000000000..8326c9fa5
--- /dev/null
+++ b/gr-pager/src/flex_demod.py
@@ -0,0 +1,57 @@
+#
+# Copyright 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., 51 Franklin Street,
+# Boston, MA 02110-1301, USA.
+# 
+
+from gnuradio import gr, optfir
+from math import pi
+import pager_swig
+
+class flex_demod(gr.hier_block):
+    """
+    FLEX protocol demodulation block.
+
+    This block demodulates a band-limited, complex down-converted baseband 
+    channel into FLEX protocol frames.
+
+    Flow graph (so far):
+
+    QUAD     - Quadrature demodulator converts FSK to baseband amplitudes  
+    LPF      - Low pass filter to remove noise prior to slicer
+    SLICER   - Converts input to one of four symbols (0, 1, 2, 3)
+    DEFRAMER - Syncronizes symbol stream and outputs FLEX codewords
+    ---
+
+    @param fg: flowgraph
+    @param channel_rate:  incoming sample rate of the baseband channel
+    @type sample_rate: integer
+    """
+
+    def __init__(self, fg, channel_rate):
+        k = channel_rate/(2*pi*4800)        # 4800 Hz max deviation
+        QUAD = gr.quadrature_demod_cf(k)
+
+        taps = optfir.low_pass(1.0, channel_rate, 3200, 6400, 0.1, 60)
+        LPF = gr.fir_filter_fff(1, taps)
+        SLICER = pager_swig.slicer_fb(.001, .00001) # Attack, decay
+        DEFRAMER = pager_swig.flex_deframer(channel_rate)
+	
+        fg.connect(QUAD, LPF, SLICER, DEFRAMER)
+
+        gr.hier_block.__init__(self, fg, QUAD, DEFRAMER)