#

# GMSK modulation and demodulation.  

#

#

# Copyright 2005,2006,2007 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.

# 

# See gnuradio-examples/python/digital for examples

from gnuradio import gr

import digital_swig

import modulation_utils

from math import pi

import numpy

from pprint import pprint

import inspect

# default values (used in __init__ and add_options)

_def_samples_per_symbol = 2

_def_bt = 0.35

_def_verbose = False

_def_log = False

# Symbol timing recovery 

_def_timing_bw = 2*pi/100.0

_def_timing_max_dev = 1.5

# /////////////////////////////////////////////////////////////////////////////

#                              GMSK modulator

# /////////////////////////////////////////////////////////////////////////////

class gmsk_mod(gr.hier_block2):

    def __init__(self,

                 samples_per_symbol=_def_samples_per_symbol,

                 bt=_def_bt,

                 verbose=_def_verbose,

                 log=_def_log):

        """

        Hierarchical block for Gaussian Minimum Shift Key (GMSK)

        modulation.

        The input is a byte stream (unsigned char) and the

        output is the complex modulated signal at baseband.

        @param samples_per_symbol: samples per baud >= 2

        @type samples_per_symbol: integer

        @param bt: Gaussian filter bandwidth * symbol time

        @type bt: float

        @param verbose: Print information about modulator?

        @type verbose: bool

        @param debug: Print modualtion data to files?

        @type debug: bool       

        """

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

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

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

        self._samples_per_symbol = samples_per_symbol

        self._bt = bt

        self._differential = False # make consistant with other modulators

        if samples_per_symbol < 2:

            raise TypeError, ("samples_per_symbol must  >= 2, is %r" % \

                                  (samples_per_symbol,))

        ntaps = 4 * samples_per_symbol                        # up to 3 bits in filter at once

        sensitivity = (pi / 2) / samples_per_symbol        # phase change per bit = pi / 2

        # Turn it into NRZ data.

        self.nrz = gr.bytes_to_syms()

        # Form Gaussian filter

        # Generate Gaussian response (Needs to be convolved with window below).

        self.gaussian_taps = gr.firdes.gaussian(

                1,                       # gain

                samples_per_symbol,    # symbol_rate

                bt,                       # bandwidth * symbol time

                int(ntaps)             # number of taps

                )

        self.sqwave = (1,) * int(samples_per_symbol)       # rectangular window

        self.taps = numpy.convolve(numpy.array(self.gaussian_taps),numpy.array(self.sqwave))

        self.gaussian_filter = gr.pfb_arb_resampler_fff(samples_per_symbol, self.taps)

        # FM modulation

        self.fmmod = gr.frequency_modulator_fc(sensitivity)

        if verbose:

            self._print_verbage()

        if log:

            self._setup_logging()

        # Connect & Initialize base class

        self.connect(self, self.nrz, self.gaussian_filter, self.fmmod, self)

    def samples_per_symbol(self):

        return self._samples_per_symbol

    def bits_per_symbol(self=None):     # staticmethod that's also callable on an instance

        return 1

    bits_per_symbol = staticmethod(bits_per_symbol)      # make it a static method.

    def _print_verbage(self):

        print "bits per symbol = %d" % self.bits_per_symbol()

        print "Gaussian filter bt = %.2f" % self._bt

    def _setup_logging(self):

        print "Modulation logging turned on."

        self.connect(self.nrz,

                     gr.file_sink(gr.sizeof_float, "tx_gmsk_nrz.32f"))

        self.connect(self.gaussian_filter,

                     gr.file_sink(gr.sizeof_float, "tx_gmsk_gaussian_filter.32f"))

        self.connect(self.fmmod,

                     gr.file_sink(gr.sizeof_gr_complex, "tx_gmsk_fmmod.32fc"))

    def add_options(parser):

        """

        Adds GMSK modulation-specific options to the standard parser

        """

        parser.add_option("", "--bt", type="float", default=_def_bt,

                          help="set bandwidth-time product [default=%default] (GMSK)")

    add_options=staticmethod(add_options)

    def extract_kwargs_from_options(options):

        """

        Given command line options, create dictionary suitable for passing to __init__

        """

        return modulation_utils.extract_kwargs_from_options(gmsk_mod.__init__,

                                                            ('self',), options)

    extract_kwargs_from_options=staticmethod(extract_kwargs_from_options)

# /////////////////////////////////////////////////////////////////////////////

#                            GMSK demodulator

# /////////////////////////////////////////////////////////////////////////////

class gmsk_demod(gr.hier_block2):

    def __init__(self,

                 samples_per_symbol=_def_samples_per_symbol,

                 bt=_def_bt,

                 timing_bw=_def_timing_bw,

                 verbose=_def_verbose,

                 log=_def_log):

        """

        Hierarchical block for Gaussian Minimum Shift Key (GMSK)

        demodulation.

        The input is the complex modulated signal at baseband.

        The output is a stream of bits packed 1 bit per byte (the LSB)

        @param samples_per_symbol: samples per baud

        @type samples_per_symbol: integer

        @param timing_bw: timing recovery loop lock-in bandwidth

        @type timing_bw: float

        @param verbose: Print information about modulator?

        @type verbose: bool

        @param log: Print modualtion data to files?

        @type log: bool 

        """

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

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

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

        self._samples_per_symbol = samples_per_symbol

        self._bt = bt

        self._timing_bw = timing_bw

        self._timing_max_dev= _def_timing_max_dev

        self._differential = False # make consistant with other modulators

        if samples_per_symbol < 2:

            raise TypeError, "samples_per_symbol >= 2, is %f" % samples_per_symbol

        # Demodulate FM

        sensitivity = (pi / 2) / samples_per_symbol

        self.fmdemod = gr.quadrature_demod_cf(1.0 / sensitivity)

        # the clock recovery block tracks the symbol clock and resamples as needed.

        # the output of the block is a stream of soft symbols (float)

        nfilts = 32

        ntaps = 11 * int(self._samples_per_symbol*nfilts) 

        taps = gr.firdes.gaussian(nfilts,

                                  nfilts*self._samples_per_symbol,

                                  self._bt, ntaps)

        self.clock_recovery = \

            gr.pfb_clock_sync_fff(self._samples_per_symbol,

                                  self._timing_bw, taps,

                                  nfilts, nfilts//2, self._timing_max_dev)

        # slice the floats at 0, outputting 1 bit (the LSB of the output byte) per sample

        self.slicer = digital_swig.binary_slicer_fb()

        if verbose:

            self._print_verbage()

        if log:

            self._setup_logging()

        # Connect & Initialize base class

        self.connect(self, self.fmdemod, self.clock_recovery, self.slicer, self)

    def samples_per_symbol(self):

        return self._samples_per_symbol

    def bits_per_symbol(self=None):   # staticmethod that's also callable on an instance

        return 1

    bits_per_symbol = staticmethod(bits_per_symbol)      # make it a static method.

    def _print_verbage(self):

        print "bits per symbol:     %d" % self.bits_per_symbol()

        print "Bandwidth-Time Prod: %f" % self._bt

        print "Timing bandwidth:    %.2e" % self._timing_bw

    def _setup_logging(self):

        print "Demodulation logging turned on."

        self.connect(self.fmdemod,

                    gr.file_sink(gr.sizeof_float, "rx_gmsk_fmdemod.32f"))

        self.connect(self.clock_recovery,

                    gr.file_sink(gr.sizeof_float, "rx_gmsk_clock_recovery.32f"))

        self.connect(self.slicer,

                    gr.file_sink(gr.sizeof_char, "rx_gmsk_slicer.8b"))

    def add_options(parser):

        """

        Adds GMSK demodulation-specific options to the standard parser

        """

        parser.add_option("", "--timing-bw", type="float", default=_def_timing_bw,

                          help="set timing symbol sync loop gain lock-in bandwidth [default=%default]")

        parser.add_option("", "--bt", type="float", default=_def_bt,

                          help="set bandwidth-time product [default=%default] (GMSK)")

    add_options=staticmethod(add_options)

    def extract_kwargs_from_options(options):

        """

        Given command line options, create dictionary suitable for passing to __init__

        """

        return modulation_utils.extract_kwargs_from_options(gmsk_demod.__init__,

                                                             ('self',), options)

    extract_kwargs_from_options=staticmethod(extract_kwargs_from_options)

#

# Add these to the mod/demod registry

#

modulation_utils.add_type_1_mod('gmsk', gmsk_mod)

modulation_utils.add_type_1_demod('gmsk', gmsk_demod)