ppm_demod tidying

# the Free Software Foundation, Inc., 51 Franklin Street,

# Boston, MA 02110-1301, USA.

#

from gnuradio import gr, gru, air

from gnuradio import gr, gru, optfir, air

from math import pi

risetime_threshold_db = 48.0   # The minimum change for pulse leading edge in dB per bit time (Assume value for 8 MHz BW)

data_rate = 1000000.0        # Data rate in bits per second

chip_rate = data_rate*2.0     # Two chips to a bit so rate is double

class ppm_demod:

class ppm_demod(gr.hier_block2):

    """

    Mode S protocol demodulation block.

    BIT      - Decodes the Pulse Position Modulation (PPM) to Mode S Data Frames

    PARITY   - Parity Checking (CRC)

    EC       - Brute Force Error Correction

    ---

    @param fg: flowgraph

    @type fg: flow graph

    @param channel_rate:  incoming sample rate of the baseband channel

    @type channel_rate: integer

    @parm theshold: minumum level for a valid pulse

    @type theshold: integer

    """

from gnuradio import gr, gru

risetime_threshold_db = 48.0   # The minimum change for pulse leading edge in dB per bit time (Assume value for 8 MHz BW)

data_rate = 1000000.0        # Data rate in bits per second

chip_rate = data_rate*2.0     # Two chips to a bit so rate is double

class ppm_demod(gr.hier_block2):

    def __init__(self, channel_rate, threshold):

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

                              gr.io_signature(1, 1, gr.sizeof_gr_complex),

        # Calculate the leading edge threshold per sample time

        leading_edge = risetime_threshold_db/(chan_rate/data_rate)

        # Calculate the number of following samples above threshold needed to make a sample a valid pulse position

        valid_pulse_position = 2

        if chan_rate == 10000000:

            valid_pulse_position = 3

        # Demodule AM with classic sqrt (I*I + Q*Q)

        # Demodulate AM with classic sqrt (I*I + Q*Q)

        self.MAG = gr.complex_to_mag()

        self.DETECT = air.ms_pulse_detect(leading_edge, threshold, valid_pulse_position) # Attack, Threshold, Pulsewidth

        self.SYNC = air.ms_preamble(chan_rate)

            self.connect(self, self.RESAMP, self.MAG, self.DETECT)

        else: 

            self.connect(self, self.MAG, self.DETECT)

        self.connect((self.DETECT, 0), (self.SYNC, 0))

        self.connect((self.DETECT, 1), (self.SYNC, 1))

        self.connect((self.SYNC, 0), (self.FRAME, 0))