From 6a7ff662745dbf0d1991366ce2cfa9244cfc6343 Mon Sep 17 00:00:00 2001
From: Rekai Musuka <rekai@musuka.dev>
Date: Mon, 14 Jun 2021 23:37:30 -0500
Subject: [PATCH] chore(sound): implement channel 2 registers

---
 src/bus.rs   | 28 +++++++++++++++++-----------
 src/sound.rs | 28 ++++++++++++++++++++--------
 2 files changed, 37 insertions(+), 19 deletions(-)

diff --git a/src/bus.rs b/src/bus.rs
index ca1bcf4..19bee14 100644
--- a/src/bus.rs
+++ b/src/bus.rs
@@ -220,12 +220,15 @@ impl BusIo for Bus {
                     0x06 => self.timer.modulo,
                     0x07 => self.timer.ctrl.into(),
                     0x0F => self.interrupt_flag().into(),
-                    0x11 => self.sound.ch1.sound_duty.into(),
-                    0x12 => self.sound.ch1.vol_envelope.into(),
+                    0x11 => self.sound.ch1.duty.into(),
+                    0x12 => self.sound.ch1.envelope.into(),
                     0x14 => self.sound.ch1.freq_hi.into(),
-                    0x24 => self.sound.control.channel.into(),
-                    0x25 => self.sound.control.output.into(),
-                    0x26 => self.sound.control.status.into(),
+                    0x16 => self.sound.ch2.duty.into(),
+                    0x17 => self.sound.ch2.envelope.into(),
+                    0x19 => self.sound.ch2.freq_hi.into(),
+                    0x24 => self.sound.ctrl.channel.into(),
+                    0x25 => self.sound.ctrl.output.into(),
+                    0x26 => self.sound.ctrl.status.into(),
                     0x40 => self.ppu.ctrl.into(),
                     0x41 => self.ppu.stat.into(),
                     0x42 => self.ppu.pos.scroll_y,
@@ -238,7 +241,6 @@ impl BusIo for Bus {
                     0x49 => self.ppu.monochrome.obj_palette_1.into(),
                     0x4A => self.ppu.pos.window_y,
                     0x4B => self.ppu.pos.window_x,
-                    0x4D => 0x00, // Reading from this address is useful on the CGB only
                     _ => unimplemented!("Unable to read {:#06X} in I/O Registers", addr),
                 }
             }
@@ -322,13 +324,17 @@ impl BusIo for Bus {
                     0x06 => self.timer.modulo = byte,
                     0x07 => self.timer.ctrl = byte.into(),
                     0x0F => self.set_interrupt_flag(byte),
-                    0x11 => self.sound.ch1.sound_duty = byte.into(),
-                    0x12 => self.sound.ch1.vol_envelope = byte.into(),
+                    0x11 => self.sound.ch1.duty = byte.into(),
+                    0x12 => self.sound.ch1.envelope = byte.into(),
                     0x13 => self.sound.ch1.freq_lo = byte.into(),
                     0x14 => self.sound.ch1.freq_hi = byte.into(),
-                    0x24 => self.sound.control.channel = byte.into(),
-                    0x25 => self.sound.control.output = byte.into(),
-                    0x26 => self.sound.control.status = byte.into(), // FIXME: Should we control which bytes are written to here?
+                    0x16 => self.sound.ch2.duty = byte.into(),
+                    0x17 => self.sound.ch2.envelope = byte.into(),
+                    0x18 => self.sound.ch2.freq_lo = byte.into(),
+                    0x19 => self.sound.ch2.freq_hi = byte.into(),
+                    0x24 => self.sound.ctrl.channel = byte.into(),
+                    0x25 => self.sound.ctrl.output = byte.into(),
+                    0x26 => self.sound.ctrl.status = byte.into(), // FIXME: Should we control which bytes are written to here?
                     0x40 => self.ppu.ctrl = byte.into(),
                     0x41 => self.ppu.stat.update(byte),
                     0x42 => self.ppu.pos.scroll_y = byte,
diff --git a/src/sound.rs b/src/sound.rs
index 74771f0..95cea93 100644
--- a/src/sound.rs
+++ b/src/sound.rs
@@ -1,9 +1,9 @@
-use crate::instruction::Cycle;
 use bitfield::bitfield;
 #[derive(Debug, Clone, Copy, Default)]
 pub(crate) struct Sound {
-    pub(crate) control: SoundControl,
+    pub(crate) ctrl: SoundControl,
     pub(crate) ch1: Channel1,
+    pub(crate) ch2: Channel2,
 }
 
 impl Sound {
@@ -53,7 +53,7 @@ impl From<u8> for FrequencyHigh {
 
 impl From<FrequencyHigh> for u8 {
     fn from(freq: FrequencyHigh) -> Self {
-        freq.0
+        freq.0 & 0x40 // Only bit 6 can be read
     }
 }
 
@@ -142,12 +142,24 @@ impl From<SoundStatus> for u8 {
 #[derive(Debug, Clone, Copy, Default)]
 pub(crate) struct Channel1 {
     /// 0xFF11 | NR11 - Channel 1 Sound length / Wave pattern duty
-    pub(crate) sound_duty: SoundDuty,
+    pub(crate) duty: SoundDuty,
     /// 0xFF12 | NR12 - Channel 1 Volume Envelope
-    pub(crate) vol_envelope: VolumeEnvelope,
-    /// 0xFF13 | NR13 - Channel 1 Frequency Low (Lower 8 bits only)
+    pub(crate) envelope: VolumeEnvelope,
+    /// 0xFF13 | NR13 - Channel 1 Frequency low (lower 8 bits only)
     pub(crate) freq_lo: FrequencyLow,
-    /// 0xFF14 | NR14 - Channel 1 Frequency High
+    /// 0xFF14 | NR14 - Channel 1 Frequency high
+    pub(crate) freq_hi: FrequencyHigh,
+}
+
+#[derive(Debug, Clone, Copy, Default)]
+pub(crate) struct Channel2 {
+    /// 0xFF16 | NR21 - Channel 2 Sound length / Wave Pattern Duty
+    pub(crate) duty: SoundDuty,
+    /// 0xFF17 | NR22 - Channel 2 Volume ENvelope
+    pub(crate) envelope: VolumeEnvelope,
+    /// 0xFF18 | NR23 - Channel 2 Frequency low (lower 8 bits only)
+    pub(crate) freq_lo: FrequencyLow,
+    /// 0xFF19 | NR24 - Channel 2 Frequency high
     pub(crate) freq_hi: FrequencyHigh,
 }
 
@@ -234,7 +246,7 @@ impl From<u8> for SoundDuty {
 
 impl From<SoundDuty> for u8 {
     fn from(duty: SoundDuty) -> Self {
-        duty.0
+        duty.0 & 0xC0 // Only bits 7 and 6 can be read
     }
 }