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João Magalhães authoredJoão Magalhães authored
apu.rs 26.61 KiB
use std::collections::VecDeque;
use crate::{gb::GameBoy, warnln};
const DUTY_TABLE: [[u8; 8]; 4] = [
[0, 0, 0, 0, 0, 0, 0, 1],
[1, 0, 0, 0, 0, 0, 0, 1],
[1, 0, 0, 0, 0, 1, 1, 1],
[0, 1, 1, 1, 1, 1, 1, 0],
];
const CH4_DIVISORS: [u8; 8] = [8, 16, 32, 48, 64, 80, 96, 112];
pub enum Channel {
Ch1,
Ch2,
Ch3,
Ch4,
}
pub struct Apu {
ch1_timer: i16,
ch1_sequence: u8,
ch1_envelope_sequence: u8,
ch1_envelope_enabled: bool,
ch1_sweep_sequence: u8,
ch1_output: u8,
ch1_sweep_slope: u8,
ch1_sweep_increase: bool,
ch1_sweep_pace: u8,
ch1_length_timer: u8,
ch1_wave_duty: u8,
ch1_pace: u8,
ch1_direction: u8,
ch1_volume: u8,
ch1_wave_length: u16,
ch1_length_stop: bool,
ch1_enabled: bool,
ch2_timer: i16,
ch2_sequence: u8,
ch2_envelope_sequence: u8,
ch2_envelope_enabled: bool,
ch2_output: u8,
ch2_length_timer: u8,
ch2_wave_duty: u8,
ch2_pace: u8,
ch2_direction: u8,
ch2_volume: u8,
ch2_wave_length: u16,
ch2_length_stop: bool,
ch2_enabled: bool,
ch3_timer: i16,
ch3_position: u8,
ch3_output: u8,
ch3_dac: bool,
ch3_length_timer: u8,
ch3_output_level: u8,
ch3_wave_length: u16,
ch3_length_stop: bool,
ch3_enabled: bool,
ch4_timer: i16,
ch4_envelope_sequence: u8,
ch4_envelope_enabled: bool,
ch4_output: u8,
ch4_length_timer: u8,
ch4_pace: u8,
ch4_direction: u8, ch4_volume: u8,
ch4_divisor: u8,
ch4_width_mode: bool,
ch4_clock_shift: u8,
ch4_lfsr: u16,
ch4_length_stop: bool,
ch4_enabled: bool,
glob_panning: u8,
right_enabled: bool,
left_enabled: bool,
ch1_out_enabled: bool,
ch2_out_enabled: bool,
ch3_out_enabled: bool,
ch4_out_enabled: bool,
wave_ram: [u8; 16],
sampling_rate: u16,
sequencer: u16,
sequencer_step: u8,
output_timer: i16,
audio_buffer: VecDeque<u8>,
audio_buffer_max: usize,
clock_freq: u32,
}
impl Apu {
pub fn new(sampling_rate: u16, buffer_size: f32, clock_freq: u32) -> Self {
Self {
ch1_timer: 0,
ch1_sequence: 0,
ch1_envelope_sequence: 0,
ch1_envelope_enabled: false,
ch1_sweep_sequence: 0,
ch1_output: 0,
ch1_sweep_slope: 0x0,
ch1_sweep_increase: false,
ch1_sweep_pace: 0x0,
ch1_length_timer: 0x0,
ch1_wave_duty: 0x0,
ch1_pace: 0x0,
ch1_direction: 0x0,
ch1_volume: 0x0,
ch1_wave_length: 0x0,
ch1_length_stop: false,
ch1_enabled: false,
ch2_timer: 0,
ch2_sequence: 0,
ch2_envelope_sequence: 0,
ch2_envelope_enabled: false,
ch2_output: 0,
ch2_length_timer: 0x0,
ch2_wave_duty: 0x0,
ch2_pace: 0x0,
ch2_direction: 0x0,
ch2_volume: 0x0,
ch2_wave_length: 0x0,
ch2_length_stop: false,
ch2_enabled: false,
ch3_timer: 0,
ch3_position: 0,
ch3_output: 0,
ch3_dac: false,
ch3_length_timer: 0x0,
ch3_output_level: 0x0, ch3_wave_length: 0x0,
ch3_length_stop: false,
ch3_enabled: false,
ch4_timer: 0,
ch4_envelope_sequence: 0,
ch4_envelope_enabled: false,
ch4_output: 0,
ch4_length_timer: 0x0,
ch4_pace: 0x0,
ch4_direction: 0x0,
ch4_volume: 0x0,
ch4_divisor: 0x0,
ch4_width_mode: false,
ch4_clock_shift: 0x0,
ch4_lfsr: 0x0,
ch4_length_stop: false,
ch4_enabled: false,
glob_panning: 0x0,
left_enabled: true,
right_enabled: true,
ch1_out_enabled: true,
ch2_out_enabled: true,
ch3_out_enabled: true,
ch4_out_enabled: true,
/// The RAM that is used to sore the wave information
/// to be used in channel 3 audio
wave_ram: [0u8; 16],
/// The rate at which audio samples are going to be
/// taken, ideally this value should be aligned with
/// the sampling rate of the output device. A typical
/// sampling rate would be of 44.1kHz.
sampling_rate,
/// Internal sequencer counter that runs at 512Hz
/// used for the activation of the tick actions.
sequencer: 0,
sequencer_step: 0,
output_timer: 0,
audio_buffer: VecDeque::with_capacity(
(sampling_rate as f32 * buffer_size) as usize * 2,
),
audio_buffer_max: (sampling_rate as f32 * buffer_size) as usize * 2,
clock_freq,
}
}
pub fn reset(&mut self) {
self.ch1_timer = 0;
self.ch1_sequence = 0;
self.ch1_envelope_sequence = 0;
self.ch1_envelope_enabled = false;
self.ch1_sweep_sequence = 0;
self.ch1_output = 0;
self.ch1_sweep_slope = 0x0;
self.ch1_sweep_increase = false;
self.ch1_sweep_pace = 0x0;
self.ch1_length_timer = 0x0;
self.ch1_wave_duty = 0x0;
self.ch1_pace = 0x0;
self.ch1_direction = 0x0;
self.ch1_volume = 0x0;
self.ch1_wave_length = 0x0;
self.ch1_length_stop = false;
self.ch1_enabled = false;
self.ch2_timer = 0;
self.ch2_sequence = 0;
self.ch2_envelope_sequence = 0;
self.ch2_envelope_enabled = false;
self.ch2_output = 0;
self.ch2_length_timer = 0x0;
self.ch2_wave_duty = 0x0;
self.ch2_pace = 0x0;
self.ch2_direction = 0x0;
self.ch2_volume = 0x0;
self.ch2_wave_length = 0x0;
self.ch2_length_stop = false;
self.ch2_enabled = false;
self.ch3_timer = 0;
self.ch3_position = 0;
self.ch3_output = 0;
self.ch3_dac = false;
self.ch3_length_timer = 0x0;
self.ch3_output_level = 0x0;
self.ch3_wave_length = 0x0;
self.ch3_length_stop = false;
self.ch3_enabled = false;
self.ch4_timer = 0;
self.ch4_envelope_sequence = 0;
self.ch4_envelope_enabled = false;
self.ch4_output = 0;
self.ch4_length_timer = 0x0;
self.ch4_pace = 0x0;
self.ch4_direction = 0x0;
self.ch4_volume = 0x0;
self.ch4_divisor = 0x0;
self.ch4_width_mode = false;
self.ch4_clock_shift = 0x0;
self.ch4_lfsr = 0x0;
self.ch4_length_stop = false;
self.ch4_enabled = false;
self.glob_panning = 0x0;
self.left_enabled = true;
self.right_enabled = true;
self.sequencer = 0;
self.sequencer_step = 0;
self.output_timer = 0;
self.clear_audio_buffer()
}
pub fn clock(&mut self, cycles: u8) {
self.sequencer += cycles as u16;
if self.sequencer >= 8192 {
// each of these steps runs at 512/8 Hz = 64Hz,
// meaning a complete loop runs at 512 Hz
match self.sequencer_step {
0 => {
self.tick_length_all();
}
1 => (),
2 => {
self.tick_ch1_sweep();
self.tick_length_all();
}
3 => (),
4 => {
self.tick_length_all();
} 5 => (),
6 => {
self.tick_ch1_sweep();
self.tick_length_all();
}
7 => {
self.tick_envelope_all();
}
_ => (),
}
self.sequencer -= 8192;
self.sequencer_step = (self.sequencer_step + 1) & 7;
}
self.tick_ch_all(cycles);
self.output_timer = self.output_timer.saturating_sub(cycles as i16);
if self.output_timer <= 0 {
// verifies if we've reached the maximum allowed size for the
// audio buffer and if that's the case an item is removed from
// the buffer (avoiding overflow) and then then the new audio
// volume item is added to the queue
if self.audio_buffer.len() >= self.audio_buffer_max {
self.audio_buffer.pop_front();
self.audio_buffer.pop_front();
}
if self.left_enabled {
self.audio_buffer.push_back(self.output());
}
if self.right_enabled {
self.audio_buffer.push_back(self.output());
}
// calculates the rate at which a new audio sample should be
// created based on the (base/CPU) clock frequency and the
// sampling rate, this is basically the amount of APU clock
// calls that should be performed until an audio sample is created
self.output_timer += (self.clock_freq as f32 / self.sampling_rate as f32) as i16;
}
}
pub fn read(&mut self, addr: u16) -> u8 {
match addr {
// 0xFF25 — NR51: Sound panning
0xff25 => self.glob_panning,
_ => {
warnln!("Reading from unknown APU location 0x{:04x}", addr);
0xff
}
}
}
pub fn write(&mut self, addr: u16, value: u8) {
match addr {
// 0xFF10 — NR10: Channel 1 sweep
0xff10 => {
self.ch1_sweep_slope = value & 0x07;
self.ch1_sweep_increase = value & 0x08 == 0x00;
self.ch1_sweep_pace = (value & 0x70) >> 4;
self.ch1_sweep_sequence = 0;
}
// 0xFF11 — NR11: Channel 1 length timer & duty cycle
0xff11 => {
self.ch1_length_timer = value & 0x3f;
self.ch1_wave_duty = (value & 0xc0) >> 6;
}
// 0xFF12 — NR12: Channel 1 volume & envelope
0xff12 => {
self.ch1_pace = value & 0x07; self.ch1_direction = (value & 0x08) >> 3;
self.ch1_volume = (value & 0xf0) >> 4;
self.ch1_envelope_enabled = self.ch1_pace > 0;
self.ch1_envelope_sequence = 0;
}
// 0xFF13 — NR13: Channel 1 wavelength low
0xff13 => {
self.ch1_wave_length = (self.ch1_wave_length & 0xff00) | value as u16;
}
// 0xFF14 — NR14: Channel 1 wavelength high & control
0xff14 => {
let length_trigger = value & 0x40 == 0x40;
let trigger = value & 0x80 == 0x80;
self.ch1_wave_length =
(self.ch1_wave_length & 0x00ff) | (((value & 0x07) as u16) << 8);
self.ch1_length_stop = value & 0x40 == 0x40;
self.ch1_enabled |= value & 0x80 == 0x80;
if trigger {
self.trigger_ch1();
}
if (length_trigger || trigger) && self.ch1_length_timer == 0 {
self.ch1_length_timer = 0;
}
}
// 0xFF16 — NR21: Channel 2 length timer & duty cycle
0xff16 => {
self.ch2_length_timer = value & 0x3f;
self.ch2_wave_duty = (value & 0xc0) >> 6;
}
// 0xFF17 — NR22: Channel 2 volume & envelope
0xff17 => {
self.ch2_pace = value & 0x07;
self.ch2_direction = (value & 0x08) >> 3;
self.ch2_volume = (value & 0xf0) >> 4;
}
// 0xFF18 — NR23: Channel 2 wavelength low
0xff18 => {
self.ch2_wave_length = (self.ch2_wave_length & 0xff00) | value as u16;
}
// 0xFF19 — NR24: Channel 2 wavelength high & control
0xff19 => {
let length_trigger = value & 0x40 == 0x40;
let trigger = value & 0x80 == 0x80;
self.ch2_wave_length =
(self.ch2_wave_length & 0x00ff) | (((value & 0x07) as u16) << 8);
self.ch2_length_stop = length_trigger;
self.ch2_enabled |= trigger;
if trigger {
self.trigger_ch2();
}
if (length_trigger || trigger) && self.ch2_length_timer == 0 {
self.ch2_length_timer = 0;
}
}
// 0xFF1A — NR30: Channel 3 DAC enable
0xff1a => {
self.ch3_dac = value & 0x80 == 0x80;
}
// 0xFF1B — NR31: Channel 3 length timer
0xff1b => {
self.ch3_length_timer = value;
}
// 0xFF1C — NR32: Channel 3 output level
0xff1c => {
self.ch3_output_level = (value & 0x60) >> 5;
}
// 0xFF1D — NR33: Channel 3 wavelength low [write-only]
0xff1d => { self.ch3_wave_length = (self.ch3_wave_length & 0xff00) | value as u16;
}
// 0xFF1E — NR34: Channel 3 wavelength high & control
0xff1e => {
let length_trigger = value & 0x40 == 0x40;
let trigger = value & 0x80 == 0x80;
self.ch3_wave_length =
(self.ch3_wave_length & 0x00ff) | (((value & 0x07) as u16) << 8);
self.ch3_length_stop = length_trigger;
self.ch3_enabled |= trigger;
if trigger {
self.trigger_ch3();
}
if (length_trigger || trigger) && self.ch3_length_timer == 0 {
self.ch3_length_timer = 0;
}
}
// 0xFF20 — NR41: Channel 4 length timer
0xff20 => {
self.ch4_length_timer = value & 0x3f;
}
// 0xFF21 — NR42: Channel 4 volume & envelope
0xff21 => {
self.ch4_pace = value & 0x07;
self.ch4_direction = (value & 0x08) >> 3;
self.ch4_volume = (value & 0xf0) >> 4;
self.ch4_envelope_enabled = self.ch4_pace > 0;
self.ch4_envelope_sequence = 0;
}
// 0xFF22 — NR43: Channel 4 frequency & randomness
0xff22 => {
self.ch4_divisor = value & 0x07;
self.ch4_width_mode = value & 0x08 == 0x08;
self.ch4_clock_shift = (value & 0xf0) >> 4;
}
// 0xFF23 — NR44: Channel 4 control
0xff23 => {
let length_trigger = value & 0x40 == 0x40;
let trigger = value & 0x80 == 0x80;
self.ch4_length_stop = length_trigger;
self.ch4_enabled |= trigger;
if trigger {
self.trigger_ch4();
}
if (length_trigger || trigger) && self.ch4_length_timer == 0 {
self.ch4_length_timer = 0;
}
}
// 0xFF24 — NR50: Master volume & VIN panning
0xff24 => {
//@TODO: Implement master volume & VIN panning
}
// 0xFF25 — NR51: Sound panning
0xff25 => {
self.glob_panning = value;
}
// 0xFF26 — NR52: Sound on/off
0xff26 => {
//@TODO: Implement sound on/off
}
// 0xFF30-0xFF3F — Wave pattern RAM
0xff30..=0xff3f => {
self.wave_ram[addr as usize & 0x000f] = value;
}
_ => warnln!("Writing in unknown APU location 0x{:04x}", addr),
} }
#[inline(always)]
pub fn output(&self) -> u8 {
self.ch1_output() + self.ch2_output() + self.ch3_output() + self.ch4_output()
}
#[inline(always)]
pub fn ch1_output(&self) -> u8 {
if self.ch1_out_enabled {
self.ch1_output
} else {
0
}
}
#[inline(always)]
pub fn ch2_output(&self) -> u8 {
if self.ch2_out_enabled {
self.ch2_output
} else {
0
}
}
#[inline(always)]
pub fn ch3_output(&self) -> u8 {
if self.ch3_out_enabled {
self.ch3_output
} else {
0
}
}
#[inline(always)]
pub fn ch4_output(&self) -> u8 {
if self.ch4_out_enabled {
self.ch4_output
} else {
0
}
}
pub fn set_ch1_enabled(&mut self, enabled: bool) {
self.ch1_out_enabled = enabled;
}
pub fn set_ch2_enabled(&mut self, enabled: bool) {
self.ch2_out_enabled = enabled;
}
pub fn set_ch3_enabled(&mut self, enabled: bool) {
self.ch3_out_enabled = enabled;
}
pub fn set_ch4_enabled(&mut self, enabled: bool) {
self.ch4_out_enabled = enabled;
}
pub fn audio_buffer(&self) -> &VecDeque<u8> {
&self.audio_buffer
}
pub fn audio_buffer_mut(&mut self) -> &mut VecDeque<u8> {
&mut self.audio_buffer
}
pub fn clear_audio_buffer(&mut self) {
self.audio_buffer.clear();
}
pub fn clock_freq(&self) -> u32 {
self.clock_freq
}
pub fn set_clock_freq(&mut self, value: u32) {
self.clock_freq = value;
}
#[inline(always)]
fn tick_length_all(&mut self) {
self.tick_length(Channel::Ch1);
self.tick_length(Channel::Ch2);
self.tick_length(Channel::Ch3);
self.tick_length(Channel::Ch4);
}
#[inline(always)]
fn tick_length(&mut self, channel: Channel) {
match channel {
Channel::Ch1 => {
if !self.ch1_enabled {
return;
}
self.ch1_length_timer = self.ch1_length_timer.saturating_add(1);
if self.ch1_length_timer >= 64 {
self.ch1_enabled = !self.ch1_length_stop;
self.ch1_length_timer = 0;
}
}
Channel::Ch2 => {
self.ch2_length_timer = self.ch2_length_timer.saturating_add(1);
if self.ch2_length_timer >= 64 {
self.ch2_enabled = !self.ch2_length_stop;
self.ch2_length_timer = 0;
}
}
Channel::Ch3 => {
self.ch3_length_timer = self.ch3_length_timer.saturating_add(1);
if self.ch3_length_timer >= 64 {
self.ch3_enabled = !self.ch3_length_stop;
self.ch3_length_timer = 0;
}
}
Channel::Ch4 => {
self.ch4_length_timer = self.ch4_length_timer.saturating_add(1);
if self.ch4_length_timer >= 64 {
self.ch4_enabled = !self.ch4_length_stop;
self.ch4_length_timer = 0;
}
}
}
}
#[inline(always)]
fn tick_envelope_all(&mut self) {
self.tick_envelope(Channel::Ch1);
self.tick_envelope(Channel::Ch2);
self.tick_envelope(Channel::Ch4);
}
#[inline(always)]
fn tick_envelope(&mut self, channel: Channel) {
match channel {
Channel::Ch1 => {
if !self.ch1_enabled || !self.ch1_envelope_enabled {
return;
}
self.ch1_envelope_sequence += 1;
if self.ch1_envelope_sequence >= self.ch1_pace { if self.ch1_direction == 0x01 {
self.ch1_volume = self.ch1_volume.saturating_add(1);
} else {
self.ch1_volume = self.ch1_volume.saturating_sub(1);
}
if self.ch1_volume == 0 || self.ch1_volume == 15 {
self.ch1_envelope_enabled = false;
}
self.ch1_envelope_sequence = 0;
}
}
Channel::Ch2 => {
if !self.ch2_enabled || !self.ch2_envelope_enabled {
return;
}
self.ch2_envelope_sequence += 1;
if self.ch2_envelope_sequence >= self.ch2_pace {
if self.ch2_direction == 0x01 {
self.ch2_volume = self.ch2_volume.saturating_add(1);
} else {
self.ch2_volume = self.ch2_volume.saturating_sub(1);
}
if self.ch2_volume == 0 || self.ch2_volume == 15 {
self.ch2_envelope_enabled = false;
}
self.ch2_envelope_sequence = 0;
}
}
Channel::Ch3 => (),
Channel::Ch4 => {
if !self.ch4_enabled || !self.ch4_envelope_enabled {
return;
}
self.ch4_envelope_sequence += 1;
if self.ch4_envelope_sequence >= self.ch4_pace {
if self.ch4_direction == 0x01 {
self.ch4_volume = self.ch4_volume.saturating_add(1);
} else {
self.ch4_volume = self.ch4_volume.saturating_sub(1);
}
if self.ch4_volume == 0 || self.ch4_volume == 15 {
self.ch4_envelope_enabled = false;
}
self.ch4_envelope_sequence = 0;
}
}
}
}
#[inline(always)]
fn tick_ch1_sweep(&mut self) {
if self.ch1_sweep_pace == 0x0 {
return;
}
self.ch1_sweep_sequence += 1;
if self.ch1_sweep_sequence >= self.ch1_sweep_pace {
let divisor = 1u16 << self.ch1_sweep_slope as u16;
let delta = (self.ch1_wave_length as f32 / divisor as f32) as u16;
if self.ch1_sweep_increase {
self.ch1_wave_length = self.ch1_wave_length.saturating_add(delta);
} else {
self.ch1_wave_length = self.ch1_wave_length.saturating_sub(delta);
}
if self.ch1_wave_length > 0x07ff {
self.ch1_enabled = false;
self.ch1_wave_length = 0x07ff;
}
self.ch1_sweep_sequence = 0;
}
}
#[inline(always)]
fn tick_ch_all(&mut self, cycles: u8) {
self.tick_ch1(cycles);
self.tick_ch2(cycles);
self.tick_ch3(cycles);
self.tick_ch4(cycles);
}
#[inline(always)]
fn tick_ch1(&mut self, cycles: u8) {
self.ch1_timer = self.ch1_timer.saturating_sub(cycles as i16);
if self.ch1_timer > 0 {
return;
}
if self.ch1_enabled {
self.ch1_output =
if DUTY_TABLE[self.ch1_wave_duty as usize][self.ch1_sequence as usize] == 1 {
self.ch1_volume
} else {
0
};
} else {
self.ch1_output = 0;
}
self.ch1_timer += ((2048 - self.ch1_wave_length) << 2) as i16;
self.ch1_sequence = (self.ch1_sequence + 1) & 7;
}
#[inline(always)]
fn tick_ch2(&mut self, cycles: u8) {
self.ch2_timer = self.ch2_timer.saturating_sub(cycles as i16);
if self.ch2_timer > 0 {
return;
}
if self.ch2_enabled {
self.ch2_output =
if DUTY_TABLE[self.ch2_wave_duty as usize][self.ch2_sequence as usize] == 1 {
self.ch2_volume
} else {
0
};
} else {
self.ch2_output = 0;
}
self.ch2_timer += ((2048 - self.ch2_wave_length) << 2) as i16;
self.ch2_sequence = (self.ch2_sequence + 1) & 7;
}
#[inline(always)]
fn tick_ch3(&mut self, cycles: u8) {
self.ch3_timer = self.ch3_timer.saturating_sub(cycles as i16);
if self.ch3_timer > 0 {
return;
}
if self.ch3_enabled && self.ch3_dac {
let wave_index = self.ch3_position >> 1;
let mut output = self.wave_ram[wave_index as usize];
output = if (self.ch3_position & 0x01) == 0x01 {
output & 0x0f
} else {
(output & 0xf0) >> 4
};
if self.ch3_output_level > 0 {
output >>= self.ch3_output_level - 1; } else {
output = 0;
}
self.ch3_output = output;
} else {
self.ch3_output = 0;
}
self.ch3_timer += ((2048 - self.ch3_wave_length) << 1) as i16;
self.ch3_position = (self.ch3_position + 1) & 31;
}
#[inline(always)]
fn tick_ch4(&mut self, cycles: u8) {
self.ch4_timer = self.ch4_timer.saturating_sub(cycles as i16);
if self.ch4_timer > 0 {
return;
}
if self.ch4_enabled {
// obtains the current value of the LFSR based as
// the XOR of the 1st and 2nd bit of the LFSR
let result = ((self.ch4_lfsr & 0x0001) ^ ((self.ch4_lfsr >> 1) & 0x0001)) == 0x0001;
// shifts the LFSR to the right and in case the
// value is positive sets the 15th bit to 1
self.ch4_lfsr >>= 1;
self.ch4_lfsr |= if result { 0x0001 << 14 } else { 0x0 };
// in case the short width mode (7 bits) is set then
// the 6th bit will be set to value of the 15th bit
if self.ch4_width_mode {
self.ch4_lfsr &= 0xbf;
self.ch4_lfsr |= if result { 0x40 } else { 0x00 };
}
self.ch4_output = if result { self.ch4_volume } else { 0 };
} else {
self.ch4_output = 0;
}
self.ch4_timer +=
((CH4_DIVISORS[self.ch4_divisor as usize] as u16) << self.ch4_clock_shift) as i16;
}
#[inline(always)]
fn trigger_ch1(&mut self) {
self.ch1_timer = ((2048 - self.ch1_wave_length) << 2) as i16;
self.ch1_envelope_sequence = 0;
self.ch1_sweep_sequence = 0;
}
#[inline(always)]
fn trigger_ch2(&mut self) {
self.ch2_timer = ((2048 - self.ch2_wave_length) << 2) as i16;
self.ch2_envelope_sequence = 0;
}
#[inline(always)]
fn trigger_ch3(&mut self) {
self.ch3_timer = 3;
self.ch3_position = 0;
}
#[inline(always)]
fn trigger_ch4(&mut self) {
self.ch4_timer =
((CH4_DIVISORS[self.ch4_divisor as usize] as u16) << self.ch4_clock_shift) as i16;
self.ch4_lfsr = 0x7ff1;
self.ch4_envelope_sequence = 0; }
}
impl Default for Apu {
fn default() -> Self {
Self::new(44100, 1.0, GameBoy::CPU_FREQ)
}
}