Class: SPCore::Oscillator

Inherits:
Object
  • Object
show all
Includes:
Hashmake::HashMakeable
Defined in:
lib/spcore/generation/oscillator.rb

Overview

Author:

  • James Tunnell

Constant Summary collapse

WAVE_SINE =

Defines a sine wave type.

:waveSine
WAVE_TRIANGLE =

Defines a triangle wave type.

:waveTriangle
WAVE_SAWTOOTH =

Defines a sawtooth wave type.

:waveSawtooth
WAVE_SQUARE =

Defines a square wave type.

:waveSquare
WAVES =

Defines a list of the valid wave types.

[WAVE_SINE, WAVE_TRIANGLE, WAVE_SAWTOOTH, WAVE_SQUARE]
ARG_SPECS =

Used to process hashed arguments in #initialize.

{
  :sample_rate => arg_spec(:reqd => true, :type => Fixnum, :validator => ->(a){ a > 0 } ),
  :wave_type => arg_spec(:reqd => false, :type => Symbol, :default => WAVE_SINE, :validator => ->(a){ WAVES.include? a } ),
  :frequency => arg_spec(:reqd => false, :type => Numeric, :default => 1.0, :validator => ->(a){ a > 0.0 } ),
  :amplitude => arg_spec(:reqd => false, :type => Numeric, :default => 1.0 ),
  :phase_offset => arg_spec(:reqd => false, :type => Numeric, :default => 0.0 ),
  :dc_offset => arg_spec(:reqd => false, :type => Numeric, :default => 0.0 ),
}
K_SINE_B =

constant used to calculate sine wave

4.0 / Math::PI
K_SINE_C =

constant used to calculate sine wave

-4.0 / (Math::PI * Math::PI)
K_SINE_P =

Q = 0.775 constant used to calculate sine wave

0.225
K_TRIANGLE_A =

constant used to calculate triangle wave

2.0 / Math::PI
K_SAWTOOTH_A =

constant used to calculate sawtooth wave

1.0 / Math::PI

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(args) ⇒ Oscillator

A new instance of Oscillator. The controllable wave parameters are frequency, amplitude, phase offset, and DC offset. The current phase angle is initialized to the given phase offset.

Parameters:

  • args (Hash) —

    Hashed arguments. Required key is :sample_rate. Optional keys are :wave_type, :frequency, :amplitude, :phase_offset, and :dc_offset. See ARG_SPECS for more details.



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# File 'lib/spcore/generation/oscillator.rb', line 40

def initialize args
  hash_make args, Oscillator::ARG_SPECS
  
  @phase_angle_incr = (@frequency * TWO_PI) / @sample_rate
  @current_phase_angle = @phase_offset
end

Instance Attribute Details

#amplitude ⇒ Object

Returns the value of attribute amplitude.



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# File 'lib/spcore/generation/oscillator.rb', line 8

def amplitude
  @amplitude
end

#dc_offset ⇒ Object

Returns the value of attribute dc_offset.



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# File 'lib/spcore/generation/oscillator.rb', line 8

def dc_offset
  @dc_offset
end

#frequency ⇒ Object

Returns the value of attribute frequency.



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# File 'lib/spcore/generation/oscillator.rb', line 9

def frequency
  @frequency
end

#phase_offset ⇒ Object

Returns the value of attribute phase_offset.



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# File 'lib/spcore/generation/oscillator.rb', line 9

def phase_offset
  @phase_offset
end

#sample_rate ⇒ Object

Returns the value of attribute sample_rate.



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# File 'lib/spcore/generation/oscillator.rb', line 9

def sample_rate
  @sample_rate
end

#wave_type ⇒ Object

Returns the value of attribute wave_type.



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# File 'lib/spcore/generation/oscillator.rb', line 8

def wave_type
  @wave_type
end

Instance Method Details

#sample ⇒ Object

Step forward one sampling period and sample the oscillator waveform.



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# File 'lib/spcore/generation/oscillator.rb', line 70

def sample
  output = 0.0

  while(@current_phase_angle < -Math::PI)
    @current_phase_angle += TWO_PI
  end

  while(@current_phase_angle > Math::PI)
    @current_phase_angle -= TWO_PI
  end

  case @wave_type
  when WAVE_SINE
    output = @amplitude * sine(@current_phase_angle) + @dc_offset
  when WAVE_TRIANGLE
    output = @amplitude * triangle(@current_phase_angle) + @dc_offset
  when WAVE_SQUARE
    output = @amplitude * square(@current_phase_angle) + @dc_offset
  when WAVE_SAWTOOTH
    output = @amplitude * sawtooth(@current_phase_angle) + @dc_offset
  else
    raise "Encountered unexpected wave type #{@wave_type}"
  end
  
  @current_phase_angle += @phase_angle_incr
  return output
end

#sawtooth(x) ⇒ Object

generate a sawtooth wave: input range: -PI to PI ouput range: -1 to 1



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# File 'lib/spcore/generation/oscillator.rb', line 142

def sawtooth x
  K_SAWTOOTH_A * x
end

#sine(x) ⇒ Object

generate a sine wave: input range: -PI to PI ouput range: -1 to 1



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# File 'lib/spcore/generation/oscillator.rb', line 109

def sine x
  y = K_SINE_B * x + K_SINE_C * x * x.abs
  # for extra precision
  y = K_SINE_P * (y * y.abs - y) + y   # Q * y + P * y * y.abs
  
  # sin normally output outputs -1 to 1, so to adjust
  # it to output 0 to 1, return (y*0.5)+0.5
  return y
end

#square(x) ⇒ Object

generate a square wave (50% duty cycle): input range: -PI to PI ouput range: 0 to 1



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# File 'lib/spcore/generation/oscillator.rb', line 132

def square x
  (x >= 0.0) ? 1.0 : -1.0
end

#triangle(x) ⇒ Object

generate a triangle wave: input range: -PI to PI ouput range: -1 to 1



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# File 'lib/spcore/generation/oscillator.rb', line 125

def triangle x
  (K_TRIANGLE_A * x).abs - 1.0
end