From 80d58ba497258d65622744003843bf8d6f952ad7 Mon Sep 17 00:00:00 2001
From: Alex Janka <alex@alexjanka.com>
Date: Tue, 28 Feb 2023 09:58:01 +1100
Subject: [PATCH] many apu improvements

---
 src/processor/memory/mmio/apu.rs          | 20 ++++++---
 src/processor/memory/mmio/apu/channels.rs | 54 +++++++++++++++++++----
 2 files changed, 60 insertions(+), 14 deletions(-)

diff --git a/src/processor/memory/mmio/apu.rs b/src/processor/memory/mmio/apu.rs
index 15bb435..0001038 100644
--- a/src/processor/memory/mmio/apu.rs
+++ b/src/processor/memory/mmio/apu.rs
@@ -251,10 +251,10 @@ impl Apu {
                 } else {
                     0b01111111
                 };
-                v = set_or_clear_bit(v, 0, self.channels.one.enabled);
-                v = set_or_clear_bit(v, 1, self.channels.two.enabled);
-                v = set_or_clear_bit(v, 2, self.channels.three.enabled);
-                v = set_or_clear_bit(v, 3, self.channels.four.enabled);
+                v = set_or_clear_bit(v, 0, self.channels.one.is_dac_enabled());
+                v = set_or_clear_bit(v, 1, self.channels.two.is_dac_enabled());
+                v = set_or_clear_bit(v, 2, self.channels.three.is_dac_enabled());
+                v = set_or_clear_bit(v, 3, self.channels.four.is_dac_enabled());
                 v
             }
             // write-only registers
@@ -303,7 +303,17 @@ impl Apu {
                 self.mixer.ch3.left = Volume::from_bool(get_bit(data, 6));
                 self.mixer.ch4.left = Volume::from_bool(get_bit(data, 7));
             }
-            0xFF26 => self.apu_enable = (1 << 7) == (data & 0b10000000),
+            0xFF26 => {
+                if !self.apu_enable {
+                    for i in 0xFF10..0xFF20 {
+                        self.mmio_write(i, 0x0);
+                    }
+                    for i in 0xFF21..0xFF25 {
+                        self.mmio_write(i, 0x0);
+                    }
+                }
+                self.apu_enable = (1 << 7) == (data & 0b10000000);
+            }
             0xFF30..0xFF40 => self.channels.three.update_wave_ram(addr, data),
             0xFF15 | 0xFF1F | 0xFF27..0xFF30 => {}
             0x0..0xFF10 | 0xFF40..=0xFFFF => panic!("non-apu addr in apu"),
diff --git a/src/processor/memory/mmio/apu/channels.rs b/src/processor/memory/mmio/apu/channels.rs
index 27c279c..301ce0d 100644
--- a/src/processor/memory/mmio/apu/channels.rs
+++ b/src/processor/memory/mmio/apu/channels.rs
@@ -146,8 +146,15 @@ impl PwmChannel {
     }
 
     fn trigger(&mut self) {
-        self.enabled = true;
+        if self.get_volume_and_envelope() & 0xF8 != 0 {
+            self.enabled = true;
+        }
         self.envelope = self.queued_envelope;
+        self.set_wave_timer();
+        self.wave_position = 0;
+        if self.length_timer >= 64 {
+            self.length_timer = 0;
+        }
     }
 
     pub fn tick(&mut self, steps: usize) -> Vec<f32> {
@@ -199,7 +206,7 @@ impl PwmChannel {
     }
 
     pub(super) fn length_tick(&mut self) {
-        if self.length_enable && self.enabled {
+        if self.length_enable {
             self.length_timer += 1;
             if self.length_timer >= 64 {
                 self.enabled = false;
@@ -244,6 +251,9 @@ impl PwmChannel {
             },
             data & 0b111,
         );
+        if data & 0b11111000 == 0 {
+            self.enabled = false;
+        }
     }
 
     pub(super) fn get_volume_and_envelope(&self) -> u8 {
@@ -276,6 +286,10 @@ impl PwmChannel {
     fn set_wave_timer(&mut self) {
         self.wave_timer = (2048 - self.wavelength) * 4;
     }
+
+    pub(super) fn is_dac_enabled(&self) -> bool {
+        self.enabled
+    }
 }
 
 #[derive(Debug, PartialEq)]
@@ -329,7 +343,7 @@ impl WaveChannel {
             enabled,
             dac_enabled: false,
             length_enable: false,
-            length_timer: 0xFF,
+            length_timer: 0,
             volume: ShiftVolumePercent::Zero,
             wavelength,
             wave_timer: (2048 - wavelength) * 2,
@@ -339,7 +353,14 @@ impl WaveChannel {
     }
 
     fn trigger(&mut self) {
-        self.enabled = true;
+        if self.dac_enabled {
+            self.enabled = true;
+        };
+        self.set_wave_timer();
+        self.wave_position = 0;
+        if self.length_timer == 0xFF {
+            self.length_timer = 0;
+        }
     }
 
     pub fn tick(&mut self, steps: usize) -> Vec<f32> {
@@ -369,9 +390,10 @@ impl WaveChannel {
     }
 
     pub(super) fn length_tick(&mut self) {
-        if self.length_enable && self.enabled {
-            self.length_timer = self.length_timer.saturating_add(1);
-            if self.length_timer == 0xFF {
+        if self.length_enable {
+            let (new, overflow) = self.length_timer.overflowing_add(1);
+            self.length_timer = new;
+            if overflow {
                 self.enabled = false;
             }
         }
@@ -437,6 +459,10 @@ impl WaveChannel {
     fn set_wave_timer(&mut self) {
         self.wave_timer = (2048 - self.wavelength) * 2;
     }
+
+    pub(super) fn is_dac_enabled(&self) -> bool {
+        self.dac_enabled && self.enabled
+    }
 }
 
 #[derive(PartialEq)]
@@ -524,9 +550,12 @@ impl NoiseChannel {
     }
 
     fn trigger(&mut self) {
-        self.enabled = true;
+        // self.enabled = true;
         self.envelope = self.queued_envelope;
         self.lfsr.register = 0;
+        if self.length_timer >= 64 {
+            self.length_timer = 0;
+        }
     }
 
     pub fn tick(&mut self, steps: usize) -> Vec<f32> {
@@ -553,7 +582,7 @@ impl NoiseChannel {
     }
 
     pub(super) fn length_tick(&mut self) {
-        if self.length_enable && self.enabled {
+        if self.length_enable {
             self.length_timer += 1;
             if self.length_timer >= 64 {
                 self.enabled = false;
@@ -575,6 +604,9 @@ impl NoiseChannel {
             },
             data & 0b111,
         );
+        if data & 0b11111000 == 0 {
+            self.enabled = false;
+        }
     }
 
     pub(super) fn get_volume_and_envelope(&self) -> u8 {
@@ -615,4 +647,8 @@ impl NoiseChannel {
     pub(super) fn get_control(&self) -> u8 {
         set_or_clear_bit(0xFF, 6, self.length_enable)
     }
+
+    pub(super) fn is_dac_enabled(&self) -> bool {
+        self.get_volume_and_envelope() & 0xF8 == 0 && self.enabled
+    }
 }