#

# Copyright 2005,2007 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 3, 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.

# 

import math

from gnuradio import gr, optfir

class standard_squelch(gr.hier_block2):

    def __init__(self, audio_rate):

        gr.hier_block2.__init__(self, "standard_squelch",

                                gr.io_signature(1, 1, gr.sizeof_float), # Input signature

                                gr.io_signature(1, 1, gr.sizeof_float)) # Output signature

        self.input_node = gr.add_const_ff(0)          # FIXME kludge

        self.low_iir = gr.iir_filter_ffd((0.0193,0,-0.0193),(1,1.9524,-0.9615))

        self.low_square = gr.multiply_ff()

        self.low_smooth = gr.single_pole_iir_filter_ff(1/(0.01*audio_rate))   # 100ms time constant

        self.hi_iir = gr.iir_filter_ffd((0.0193,0,-0.0193),(1,1.3597,-0.9615))

        self.hi_square = gr.multiply_ff()

        self.hi_smooth = gr.single_pole_iir_filter_ff(1/(0.01*audio_rate))

        self.sub = gr.sub_ff();

        self.add = gr.add_ff();

        self.gate = gr.threshold_ff(0.3,0.43,0)

        self.squelch_lpf = gr.single_pole_iir_filter_ff(1/(0.01*audio_rate))

        self.div = gr.divide_ff()

        self.squelch_mult = gr.multiply_ff()

        self.connect (self, self.input_node)

        self.connect (self.input_node, (self.squelch_mult, 0))

        self.connect (self.input_node,self.low_iir)

        self.connect (self.low_iir,(self.low_square,0))

        self.connect (self.low_iir,(self.low_square,1))

        self.connect (self.low_square,self.low_smooth,(self.sub,0))

        self.connect (self.low_smooth, (self.add,0))

        self.connect (self.input_node,self.hi_iir)

        self.connect (self.hi_iir,(self.hi_square,0))

        self.connect (self.hi_iir,(self.hi_square,1))

        self.connect (self.hi_square,self.hi_smooth,(self.sub,1))

        self.connect (self.hi_smooth, (self.add,1))

        self.connect (self.sub, (self.div, 0))

        self.connect (self.add, (self.div, 1))

        self.connect (self.div, self.gate, self.squelch_lpf, (self.squelch_mult,1))

        self.connect (self.squelch_mult, self)

    def set_threshold(self, threshold):

        self.gate.set_hi(threshold)

    def threshold(self):

        return self.gate.hi()

    def squelch_range(self):

        return (0.0, 1.0, 1.0/100)