Class: Radio::PSK31::Decoder

Inherits:
Object
  • Object
show all
Defined in:
lib/radio/psk31/decoder.rb

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize ⇒ Decoder

Returns a new instance of Decoder.



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# File 'lib/radio/psk31/decoder.rb', line 23

def initialize
  @mode = :bpsk 
  reset
end

Instance Attribute Details

#mode ⇒ Object

:bpsk or :qpsk or :qpsklsb



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# File 'lib/radio/psk31/decoder.rb', line 21

def mode
  @mode
end

Instance Method Details

#call(iq) ⇒ Object 



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# File 'lib/radio/psk31/decoder.rb', line 37

def call iq
  @prev_i = @this_i
  @prev_q = @this_q
  @this_i = iq.real
  @this_q = iq.imag
  vect_y = @prev_i*@this_i + @prev_q*@this_q
  if @mode == :bpsk
    bit = vect_y >= 0.0 ? 1 : 0
  else
    vect_x = @prev_i*@this_q - @this_i*@prev_q
    if vect_y == 0.0 # atan2 errors on (0,0)
      angle = PI
    elsif @mode == :qpsklsb
      angle = PI + Math.atan2(vect_y, -vect_x)
    else # :qpsk or :bpsk
      angle = PI + Math.atan2(vect_y, vect_x)
    end
    bit = viterbi angle
  end
  if bit==0 and @prev_bit==0
    if @code != 0
      @code >>= 2
      @code &= 0x07FF
      ch = VARICODE_DECODE_TABLE[@code]
      yield ch if ch
      @code = 0
    end
  else
    @code <<= 1
    @code |= bit
    @prev_bit = bit
  end
end

#reset ⇒ Object 



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# File 'lib/radio/psk31/decoder.rb', line 28

def reset
  @prev_i = 0.0
  @prev_q = 0.0
  @this_i = 0.0
  @this_q = 0.0
  @code = 0
  @prev_bit = false
end