Class: Rubyboy::Apu

Inherits:
Object
  • Object
show all
Defined in:
lib/rubyboy/apu.rb

Instance Method Summary collapse

Constructor Details

#initialize ⇒ Apu

Returns a new instance of Apu.



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# File 'lib/rubyboy/apu.rb', line 11

def initialize
  @audio = Audio.new
  @nr50 = 0
  @nr51 = 0
  @cycles = 0
  @sampling_cycles = 0
  @fs = 0
  @samples = Array.new(1024, 0.0)
  @sample_idx = 0
  @channel1 = ApuChannels::Channel1.new
  @channel2 = ApuChannels::Channel2.new
  @channel3 = ApuChannels::Channel3.new
  @channel4 = ApuChannels::Channel4.new
end

Instance Method Details

#read_byte(addr) ⇒ Object 



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# File 'lib/rubyboy/apu.rb', line 76

def read_byte(addr)
  case addr
  when 0xff10..0xff14 then @channel1.read_nr1x(addr - 0xff10)
  when 0xff15..0xff19 then @channel2.read_nr2x(addr - 0xff15)
  when 0xff1a..0xff1e then @channel3.read_nr3x(addr - 0xff1a)
  when 0xff1f..0xff23 then @channel4.read_nr4x(addr - 0xff1f)
  when 0xff24 then @nr50
  when 0xff25 then @nr51
  when 0xff26 then (@channel1.enabled ? 0x01 : 0x00) | (@channel2.enabled ? 0x02 : 0x00) | (@channel3.enabled ? 0x04 : 0x00) | (@channel4.enabled ? 0x08 : 0x00) | 0x70 | (@enabled ? 0x80 : 0x00)
  when 0xff30..0xff3f then @channel3.wave_ram[(addr - 0xff30)]
  else raise "Invalid APU read at #{addr.to_s(16)}"
  end
end

#step(cycles) ⇒ Object 



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# File 'lib/rubyboy/apu.rb', line 26

def step(cycles)
  @cycles += cycles
  @sampling_cycles += cycles

  @channel1.step(cycles)
  @channel2.step(cycles)
  @channel3.step(cycles)
  @channel4.step(cycles)

  if @cycles >= 0x2000
    @cycles -= 0x2000

    @channel1.step_fs(@fs)
    @channel2.step_fs(@fs)
    @channel3.step_fs(@fs)
    @channel4.step_fs(@fs)

    @fs = (@fs + 1) % 8
  end

  if @sampling_cycles >= 87
    @sampling_cycles -= 87

    left_sample = (
      @nr51[7] * @channel4.dac_output +
      @nr51[6] * @channel3.dac_output +
      @nr51[5] * @channel2.dac_output +
      @nr51[4] * @channel1.dac_output
    ) / 4.0

    right_sample = (
      @nr51[3] * @channel4.dac_output +
      @nr51[2] * @channel3.dac_output +
      @nr51[1] * @channel2.dac_output +
      @nr51[0] * @channel1.dac_output
    ) / 4.0

    raise "#{@nr51} #{@channel4.dac_output}, #{@channel3.dac_output}, #{@channel2.dac_output},#{@channel1.dac_output}" if left_sample.abs > 1.0 || right_sample.abs > 1.0

    @samples[@sample_idx * 2] = (@nr50[4..6] / 7.0) * left_sample / 8.0
    @samples[@sample_idx * 2 + 1] = (@nr50[0..2] / 7.0) * right_sample / 8.0
    @sample_idx += 1
  end

  return if @sample_idx < 512

  @sample_idx = 0
  @audio.queue(@samples)
end

#write_byte(addr, val) ⇒ Object 



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# File 'lib/rubyboy/apu.rb', line 90

def write_byte(addr, val)
  return if !@enabled && ![0xff11, 0xff16, 0xff1b, 0xff20, 0xff26].include?(addr) && !(0xff30..0xff3f).include?(addr)

  val &= 0x3f if !@enabled && [0xff11, 0xff16, 0xff1b, 0xff20].include?(addr)

  case addr
  when 0xff10..0xff14 then @channel1.write_nr1x(addr - 0xff10, val)
  when 0xff15..0xff19 then @channel2.write_nr2x(addr - 0xff15, val)
  when 0xff1a..0xff1e then @channel3.write_nr3x(addr - 0xff1a, val)
  when 0xff1f..0xff23 then @channel4.write_nr4x(addr - 0xff1f, val)
  when 0xff24 then @nr50 = val
  when 0xff25 then @nr51 = val
  when 0xff26
    flg = val & 0x80 > 0
    if !flg && @enabled
      (0xff10..0xff25).each { |a| write_byte(a, 0) }
    elsif flg && !@enabled
      @fs = 0
      @channel1.wave_duty_position = 0
      @channel2.wave_duty_position = 0
      @channel3.wave_duty_position = 0
    end
    @enabled = flg
  when 0xff30..0xff3f then @channel3.wave_ram[(addr - 0xff30)] = val
  else raise "Invalid APU write at #{addr.to_s(16)}"
  end
end