#
# 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)