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chore(apu): improve accuracy of Channel 1

This commit is contained in:
Rekai Nyangadzayi Musuka 2021-10-30 21:53:08 +09:00
parent 32405c0734
commit 80a15039e0
2 changed files with 84 additions and 91 deletions
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123
src/apu.rs
View File

@ -7,7 +7,7 @@ use types::ch3::Volume as Ch3Volume;
use types::ch4::{CounterWidth, Frequency as Ch4Frequency, PolynomialCounter};
use types::common::{EnvelopeDirection, FrequencyHigh, SoundDuty, VolumeEnvelope};
use types::fs::{FrameSequencer, State as FSState};
use types::{ChannelControl, SoundOutput};
use types::{ChannelControl, NRx4, SoundOutput};
pub mod gen;
mod types;
@ -82,7 +82,7 @@ impl BusIo for Apu {
0x20 if self.ctrl.enabled => self.ch4.set_len(byte),
0x21 if self.ctrl.enabled => self.ch4.set_envelope(byte),
0x22 if self.ctrl.enabled => self.ch4.set_poly(byte),
0x23 if self.ctrl.enabled => self.ch4.set_frequency(byte),
0x23 if self.ctrl.enabled => self.ch4.set_frequency(&self.fs, byte),
0x24 if self.ctrl.enabled => self.ctrl.set_channel(byte),
0x25 if self.ctrl.enabled => self.ctrl.set_output(byte),
0x26 => self.set_status(byte),
@ -225,8 +225,8 @@ impl Apu {
self.ch4.enabled = Default::default();
}
fn process_length(freq_hi: &FrequencyHigh, counter: &mut u16, enabled: &mut bool) {
if freq_hi.length_enable() && *counter > 0 {
fn process_length(freq: &impl NRx4, counter: &mut u16, enabled: &mut bool) {
if freq.length_enable() && *counter > 0 {
*counter -= 1;
// Check in this scope ensures (only) the above subtraction
@ -237,18 +237,6 @@ impl Apu {
}
}
fn ch4_process_length(freq: &Ch4Frequency, length_timer: &mut u16, enabled: &mut bool) {
if freq.length_enable() && *length_timer > 0 {
*length_timer -= 1;
// Check in this scope ensures (only) the above subtraction
// made length_timer 0
if *length_timer == 0 {
*enabled = false;
}
}
}
fn clock_length(&mut self) {
Self::process_length(
&self.ch1.freq_hi,
@ -268,9 +256,9 @@ impl Apu {
&mut self.ch3.enabled,
);
Self::ch4_process_length(
Self::process_length(
&self.ch4.freq,
&mut self.ch4.length_timer,
&mut self.ch4.length_counter,
&mut self.ch4.enabled,
);
}
@ -287,7 +275,7 @@ impl Apu {
if self.ch1.sweep_enabled && period != 0 {
let new_freq = self.ch1.calc_sweep_freq();
if new_freq <= 2047 && self.ch1.sweep.shift_count() != 0 {
if new_freq <= 0x7FF && self.ch1.sweep.shift_count() != 0 {
self.ch1.set_frequency(new_freq);
self.ch1.shadow_freq = new_freq;
@ -485,24 +473,17 @@ impl Channel1 {
/// 0xFF14 | NR14 - Channel 1 Frequency high
pub(crate) fn set_freq_hi(&mut self, fs: &FrameSequencer, byte: u8) {
let prev_le = self.freq_hi.length_enable();
self.freq_hi = byte.into();
obscure::nrx4::length_update(
&mut self.freq_hi,
fs,
&mut self.length_counter,
&mut self.enabled,
prev_le,
);
let mut new_freq: FrequencyHigh = byte.into();
// If this bit is set, a trigger event occurs
if self.freq_hi.trigger() {
if new_freq.trigger() {
self.enabled = true;
// Length behaviour during trigger event
if self.length_counter == 0 {
self.length_counter = obscure::length_reload(&self.freq_hi, fs, 64);
self.length_counter = 64;
// length_counter was 0 so length evidently wasn't enabled
self.freq_hi.set_length_enable(false);
};
// reload freq_timer but last two bits are unmodified
@ -529,6 +510,16 @@ impl Channel1 {
self.enabled = self.is_dac_enabled();
}
obscure::nrx4::length_update(
&mut new_freq,
fs,
&mut self.length_counter,
&mut self.enabled,
self.freq_hi.length_enable(),
);
self.freq_hi = new_freq;
}
fn tick(&mut self) {
@ -664,7 +655,7 @@ impl Channel2 {
// Reload length counter if need be
if self.length_counter == 0 {
self.length_counter = obscure::length_reload(&self.freq_hi, fs, 64);
self.length_counter = 64;
}
// reload frequency timer
@ -822,7 +813,7 @@ impl Channel3 {
// Length behaviour during trigger event
if self.length_counter == 0 {
self.length_counter = obscure::length_reload(&self.freq_hi, fs, 256);
self.length_counter = 256;
}
self.freq_timer = (2048 - self.frequency()) * 2;
@ -889,7 +880,7 @@ pub(crate) struct Channel4 {
current_volume: u8,
// Length Functionality
length_timer: u16,
length_counter: u16,
/// Linear Feedback Shift Register (15-bit)
lf_shift: u16,
@ -903,7 +894,7 @@ impl Channel4 {
/// 0xFF20 | NR41 - Channel 4 Sound Length
pub(crate) fn set_len(&mut self, byte: u8) {
self.len = byte & 0x3F;
self.length_timer = 64 - self.len as u16;
self.length_counter = 64 - self.len as u16;
}
/// 0xFF21 | NR42 - Channel 4 Volume Envelope
@ -936,25 +927,37 @@ impl Channel4 {
}
/// 0xFF23 | NR44 - Channel 4 Counter / Consecutive Selector and Restart
pub(crate) fn set_frequency(&mut self, byte: u8) {
pub(crate) fn set_frequency(&mut self, fs: &FrameSequencer, byte: u8) {
let prev_le = self.freq.length_enable();
self.freq = byte.into();
if self.freq.initial() {
// Envelope behaviour during trigger event
obscure::nrx4::length_update(
&mut self.freq,
fs,
&mut self.length_counter,
&mut self.enabled,
prev_le,
);
if self.freq.trigger() {
self.enabled = true;
if self.length_counter == 0 {
self.length_counter = 64;
}
// FIXME: Frequency Timer reloaded?
// reload envelope
self.period_timer = self.envelope.period();
//reload volume
self.current_volume = self.envelope.init_vol();
// Length behaviour during trigger event
if self.length_timer == 0 {
self.length_timer = 64;
}
// LFSR behaviour during trigger event
// LFSR reset
self.lf_shift = 0x7FFF;
if self.is_dac_enabled() {
self.enabled = true;
}
self.enabled = self.is_dac_enabled();
}
}
@ -1001,8 +1004,6 @@ impl Channel4 {
}
mod obscure {
use super::{FrameSequencer, FrequencyHigh};
pub(super) mod square {
pub(crate) fn freq_timer_reload(freq_timer: u16, frequency: u16) -> u16 {
(freq_timer & 0x0003) | (((2048 - frequency) * 4) & 0xFFFC)
@ -1010,7 +1011,7 @@ mod obscure {
}
pub(super) mod nrx4 {
use super::super::{FrameSequencer, FrequencyHigh};
use super::super::{FrameSequencer, NRx4};
/// Implements the obscure behaviour when writing to NRX4 under certain
/// conditions
@ -1021,29 +1022,19 @@ mod obscure {
/// * `counter` - mutable reference to a channel's internal enabled flag
/// * `prev_le` - what length_enable was before NRx4 was written with a new value
pub(crate) fn length_update(
freq_hi: &mut FrequencyHigh,
freq: &mut impl NRx4,
fs: &FrameSequencer,
counter: &mut u16,
enabled: &mut bool,
prev_le: bool,
) {
if !fs.next_clocks_length() {
if !prev_le && freq_hi.length_enable() && *counter != 0 {
*counter -= 1;
if !fs.next_clocks_length() && !prev_le && freq.length_enable() && *counter != 0 {
*counter -= 1;
if *counter == 0 && !freq_hi.trigger() {
*enabled = false;
}
if *counter == 0 && !freq.trigger() {
*enabled = false;
}
}
}
}
pub(crate) fn length_reload(freq_hi: &FrequencyHigh, fs: &FrameSequencer, default: u16) -> u16 {
if !fs.next_clocks_length() && freq_hi.length_enable() {
default - 1
} else {
default
}
}
}

52
src/apu/types.rs
View File

@ -1,5 +1,11 @@
use bitfield::bitfield;
pub(crate) trait NRx4 {
fn trigger(&self) -> bool;
fn length_enable(&self) -> bool;
fn set_length_enable(&mut self, value: bool);
}
pub(crate) mod ch1 {
use super::bitfield;
@ -103,7 +109,7 @@ pub(super) mod ch3 {
}
pub(super) mod ch4 {
use super::bitfield;
use super::{bitfield, NRx4};
bitfield! {
pub struct PolynomialCounter(u8);
@ -177,17 +183,21 @@ pub(super) mod ch4 {
bitfield! {
pub struct Frequency(u8);
impl Debug;
_initial, _: 7;
_length_enable, _: 6;
_trigger, _: 7;
_length_enable, _set_length_enable: 6;
}
impl Frequency {
pub(crate) fn length_enable(&self) -> bool {
impl NRx4 for Frequency {
fn trigger(&self) -> bool {
self._trigger()
}
fn length_enable(&self) -> bool {
self._length_enable()
}
pub(crate) fn initial(&self) -> bool {
self._initial()
fn set_length_enable(&mut self, value: bool) {
self._set_length_enable(value);
}
}
@ -218,24 +228,28 @@ pub(super) mod ch4 {
}
pub(super) mod common {
use super::bitfield;
use super::{bitfield, NRx4};
bitfield! {
pub struct FrequencyHigh(u8);
impl Debug;
_trigger, _: 7;
_length_enable, _: 6;
_length_enable, _set_length_enable: 6;
pub freq_bits, set_freq_bits: 2, 0;
}
impl FrequencyHigh {
pub(crate) fn trigger(&self) -> bool {
impl NRx4 for FrequencyHigh {
fn trigger(&self) -> bool {
self._trigger()
}
pub(crate) fn length_enable(&self) -> bool {
fn length_enable(&self) -> bool {
self._length_enable()
}
fn set_length_enable(&mut self, value: bool) {
self._set_length_enable(value);
}
}
impl Copy for FrequencyHigh {}
@ -557,22 +571,10 @@ pub(super) mod fs {
};
}
fn peek(&self) -> State {
use State::*;
match (self.step + 1) % 8 {
1 | 3 | 5 => Nothing,
0 | 4 => Length,
2 | 6 => LengthAndSweep,
7 => Envelope,
num => unreachable!("Step {} is invalid for the Frame Sequencer", num),
}
}
pub(crate) fn next_clocks_length(&self) -> bool {
use State::*;
match self.peek() {
match self.state {
Length | LengthAndSweep => true,
Nothing | Envelope => false,
}