diff --git a/frontends/sdl/src/main.rs b/frontends/sdl/src/main.rs
index 66a89f1be880771b41fe6e4882d245a93699ec7e..8900eb0bd6355851581fd7a7459a286335e7d5d7 100644
--- a/frontends/sdl/src/main.rs
+++ b/frontends/sdl/src/main.rs
@@ -719,7 +719,7 @@ struct Args {
)]
cycles: u64,
- #[arg(short, long, default_value_t = String::from("C:/Users/joamag/Desktop/gb-test-roms/dmg_sound/rom_singles/02-len ctr.gb"), help = "Path to the ROM file to be loaded")]
+ #[arg(short, long, default_value_t = String::from("C:/Users/joamag/Desktop/gb-test-roms/dmg_sound/rom_singles/03-trigger.gb"), help = "Path to the ROM file to be loaded")]
rom_path: String,
}
diff --git a/src/apu.rs b/src/apu.rs
index efa48fcd4146da7d2c0c53fcd48347158f9707ac..cb8038c615f803cd9c5933dfff9bdad9eb8e7d51 100644
--- a/src/apu.rs
+++ b/src/apu.rs
@@ -468,7 +468,7 @@ impl Apu {
}
// 0xFF11 — NR11: Channel 1 length timer & duty cycle
0xff11 => {
- self.ch1_length_timer = value & 0x3f;
+ self.ch1_length_timer = 64 - (value & 0x3f);
self.ch1_wave_duty = (value & 0xc0) >> 6;
}
// 0xFF12 — NR12: Channel 1 volume & envelope
@@ -491,14 +491,18 @@ impl Apu {
0xff14 => {
let length_trigger = value & 0x40 == 0x40;
let trigger = value & 0x80 == 0x80;
+ let length_edge = length_trigger && !self.ch1_length_enabled;
self.ch1_wave_length =
(self.ch1_wave_length & 0x00ff) | (((value & 0x07) as u16) << 8);
self.ch1_length_enabled = value & 0x40 == 0x40;
self.ch1_enabled |= value & 0x80 == 0x80;
+ if length_edge && self.sequencer_step % 2 == 1 {
+ self.tick_length(Channel::Ch1);
+ }
if trigger {
self.trigger_ch1();
}
- if length_trigger && self.ch1_length_timer >= 64 {
+ if length_trigger && self.ch1_length_timer == 0 {
self.ch1_enabled = false;
}
}
@@ -507,7 +511,7 @@ impl Apu {
0xff15 => (),
// 0xFF16 — NR21: Channel 2 length timer & duty cycle
0xff16 => {
- self.ch2_length_timer = value & 0x3f;
+ self.ch2_length_timer = 64 - (value & 0x3f);
self.ch2_wave_duty = (value & 0xc0) >> 6;
}
// 0xFF17 — NR22: Channel 2 volume & envelope
@@ -530,14 +534,18 @@ impl Apu {
0xff19 => {
let length_trigger = value & 0x40 == 0x40;
let trigger = value & 0x80 == 0x80;
+ let length_edge = length_trigger && !self.ch2_length_enabled;
self.ch2_wave_length =
(self.ch2_wave_length & 0x00ff) | (((value & 0x07) as u16) << 8);
self.ch2_length_enabled = length_trigger;
self.ch2_enabled |= trigger;
+ if length_edge && self.sequencer_step % 2 == 1 {
+ self.tick_length(Channel::Ch2);
+ }
if trigger {
self.trigger_ch2();
}
- if length_trigger && self.ch2_length_timer >= 64 {
+ if length_trigger && self.ch2_length_timer == 0 {
self.ch2_enabled = false;
}
}
@@ -551,7 +559,7 @@ impl Apu {
}
// 0xFF1B — NR31: Channel 3 length timer
0xff1b => {
- self.ch3_length_timer = value as u16;
+ self.ch3_length_timer = 256 - (value as u16);
}
// 0xFF1C — NR32: Channel 3 output level
0xff1c => {
@@ -565,14 +573,18 @@ impl Apu {
0xff1e => {
let length_trigger = value & 0x40 == 0x40;
let trigger = value & 0x80 == 0x80;
+ let length_edge = length_trigger && !self.ch3_length_enabled;
self.ch3_wave_length =
(self.ch3_wave_length & 0x00ff) | (((value & 0x07) as u16) << 8);
self.ch3_length_enabled = length_trigger;
self.ch3_enabled |= trigger;
+ if length_edge && self.sequencer_step % 2 == 1 {
+ self.tick_length(Channel::Ch3);
+ }
if trigger {
self.trigger_ch3();
}
- if length_trigger && self.ch3_length_timer >= 256 {
+ if length_trigger && self.ch3_length_timer == 0 {
self.ch3_enabled = false;
}
}
@@ -581,7 +593,7 @@ impl Apu {
0xff1f => (),
// 0xFF20 — NR41: Channel 4 length timer
0xff20 => {
- self.ch4_length_timer = value & 0x3f;
+ self.ch4_length_timer = 64 - (value & 0x3f);
}
// 0xFF21 — NR42: Channel 4 volume & envelope
0xff21 => {
@@ -605,12 +617,16 @@ impl Apu {
0xff23 => {
let length_trigger = value & 0x40 == 0x40;
let trigger = value & 0x80 == 0x80;
+ let length_edge = length_trigger && !self.ch4_length_enabled;
self.ch4_length_enabled = length_trigger;
self.ch4_enabled |= trigger;
+ if length_edge && self.sequencer_step % 2 == 1 {
+ self.tick_length(Channel::Ch4);
+ }
if trigger {
self.trigger_ch4();
}
- if length_trigger && self.ch4_length_timer >= 64 {
+ if length_trigger && self.ch4_length_timer == 0 {
self.ch4_enabled = false;
}
}
@@ -746,43 +762,39 @@ impl Apu {
fn tick_length(&mut self, channel: Channel) {
match channel {
Channel::Ch1 => {
- if !self.ch1_length_enabled {
+ if !self.ch1_length_enabled || self.ch1_length_timer == 0 {
return;
}
- self.ch1_length_timer = self.ch1_length_timer.saturating_add(1);
- if self.ch1_length_timer >= 64 {
+ self.ch1_length_timer = self.ch1_length_timer.saturating_sub(1);
+ if self.ch1_length_timer == 0 {
self.ch1_enabled = false;
- self.ch1_length_timer = 0;
}
}
Channel::Ch2 => {
- if !self.ch2_length_enabled {
+ if !self.ch2_length_enabled || self.ch2_length_timer == 0 {
return;
}
- self.ch2_length_timer = self.ch2_length_timer.saturating_add(1);
- if self.ch2_length_timer >= 64 {
+ self.ch2_length_timer = self.ch2_length_timer.saturating_sub(1);
+ if self.ch2_length_timer == 0 {
self.ch2_enabled = false;
- self.ch2_length_timer = 0;
}
}
Channel::Ch3 => {
- if !self.ch3_length_enabled {
+ if !self.ch3_length_enabled || self.ch3_length_timer == 0 {
return;
}
- self.ch3_length_timer = self.ch3_length_timer.saturating_add(1);
- if self.ch3_length_timer >= 256 {
+ self.ch3_length_timer = self.ch3_length_timer.saturating_sub(1);
+ if self.ch3_length_timer == 0 {
self.ch3_enabled = false;
- self.ch3_length_timer = 0;
}
}
Channel::Ch4 => {
- if !self.ch4_length_enabled {
+ if !self.ch4_length_enabled || self.ch4_length_timer == 0 {
return;
}
- self.ch4_length_timer = self.ch4_length_timer.saturating_add(1);
- if self.ch4_length_timer >= 64 {
+ self.ch4_length_timer = self.ch4_length_timer.saturating_sub(1);
+ if self.ch4_length_timer == 0 {
self.ch4_enabled = false;
- self.ch4_length_timer = 0;
}
}
}
@@ -994,18 +1006,42 @@ impl Apu {
self.ch1_timer = ((2048 - self.ch1_wave_length) << 2) as i16;
self.ch1_envelope_sequence = 0;
self.ch1_sweep_sequence = 0;
+
+ let unfreeze = self.ch1_length_timer == 0;
+ if unfreeze {
+ self.ch1_length_timer = 64;
+ if self.ch1_length_enabled && self.sequencer_step % 2 == 1 {
+ self.tick_length(Channel::Ch1);
+ }
+ }
}
#[inline(always)]
fn trigger_ch2(&mut self) {
self.ch2_timer = ((2048 - self.ch2_wave_length) << 2) as i16;
self.ch2_envelope_sequence = 0;
+
+ let unfreeze = self.ch2_length_timer == 0;
+ if unfreeze {
+ self.ch2_length_timer = 64;
+ if self.ch2_length_enabled && self.sequencer_step % 2 == 1 {
+ self.tick_length(Channel::Ch2);
+ }
+ }
}
#[inline(always)]
fn trigger_ch3(&mut self) {
self.ch3_timer = 3;
self.ch3_position = 0;
+
+ let unfreeze = self.ch3_length_timer == 0;
+ if unfreeze {
+ self.ch3_length_timer = 256;
+ if self.ch3_length_enabled && self.sequencer_step % 2 == 1 {
+ self.tick_length(Channel::Ch3);
+ }
+ }
}
#[inline(always)]
@@ -1014,6 +1050,14 @@ impl Apu {
((CH4_DIVISORS[self.ch4_divisor as usize] as u16) << self.ch4_clock_shift) as i32;
self.ch4_lfsr = 0x7ff1;
self.ch4_envelope_sequence = 0;
+
+ let unfreeze = self.ch4_length_timer == 0;
+ if unfreeze {
+ self.ch4_length_timer = 64;
+ if self.ch4_length_enabled && self.sequencer_step % 2 == 1 {
+ self.tick_length(Channel::Ch4);
+ }
+ }
}
}