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#
# 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, gru, optfir, blks
from math import pi
import pager_swig
chan_rate = 16000
class flex_demod:
"""
FLEX pager protocol demodulation block.
This block demodulates a band-limited, complex down-converted baseband
channel into FLEX protocol frames.
Flow graph (so far):
RSAMP - Resample incoming stream to 16000 sps
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)
SYNC - Converts symbol stream to four phases of FLEX blocks
DEINTx - Deinterleaves FLEX blocks into datawords
PARSEx - Parse a single FLEX phase worth of data words into pages
---
@param fg: flowgraph
@param channel_rate: incoming sample rate of the baseband channel
@type sample_rate: integer
"""
def __init__(self, fg, channel_rate, queue):
k = chan_rate/(2*pi*4800) # 4800 Hz max deviation
QUAD = gr.quadrature_demod_cf(k)
self.INPUT = QUAD
if channel_rate != chan_rate:
interp = gru.lcm(channel_rate, chan_rate)/channel_rate
decim = gru.lcm(channel_rate, chan_rate)/chan_rate
RESAMP = blks.rational_resampler_ccf(fg, interp, decim)
self.INPUT = RESAMP
taps = optfir.low_pass(1.0, chan_rate, 3200, 6400, 0.1, 60)
LPF = gr.fir_filter_fff(1, taps)
SLICER = pager_swig.slicer_fb(.001, .00001) # Attack, decay
SYNC = pager_swig.flex_sync(chan_rate)
if channel_rate != chan_rate:
fg.connect(RESAMP, QUAD, LPF, SLICER, SYNC)
else:
fg.connect(QUAD, LPF, SLICER, SYNC)
DEINTA = pager_swig.flex_deinterleave()
PARSEA = pager_swig.flex_parse(queue)
DEINTB = pager_swig.flex_deinterleave()
PARSEB = pager_swig.flex_parse(queue)
DEINTC = pager_swig.flex_deinterleave()
PARSEC = pager_swig.flex_parse(queue)
DEINTD = pager_swig.flex_deinterleave()
PARSED = pager_swig.flex_parse(queue)
fg.connect((SYNC, 0), DEINTA, PARSEA)
fg.connect((SYNC, 1), DEINTB, PARSEB)
fg.connect((SYNC, 2), DEINTC, PARSEC)
fg.connect((SYNC, 3), DEINTD, PARSED)
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