feat: define APU registers

src/apu.zig

@@ -0,0 +1,144 @@
+const std = @import("std");
+
+const SoundFifo = std.fifo.LinearFifo(u8, .{ .Static = 0x20 });
+
+const io = @import("bus/io.zig");
+
+pub const Apu = struct {
+    const Self = @This();
+
+    ch1: ToneSweep,
+    ch2: Tone,
+    ch3: Wave,
+    ch4: Noise,
+    chA: DmaSound,
+    chB: DmaSound,
+
+    bias: io.SoundBias,
+    ch_vol_cnt: io.ChannelVolumeControl,
+    dma_cnt: io.DmaSoundControl,
+    cnt: io.SoundControl,
+
+    pub fn init() Self {
+        return .{
+            .ch1 = ToneSweep.init(),
+            .ch2 = Tone.init(),
+            .ch3 = Wave.init(),
+            .ch4 = Noise.init(),
+            .chA = DmaSound.init(),
+            .chB = DmaSound.init(),
+
+            .ch_vol_cnt = .{ .raw = 0 },
+            .dma_cnt = .{ .raw = 0 },
+            .cnt = .{ .raw = 0 },
+            .bias = .{ .raw = 0x0200 },
+        };
+    }
+
+    pub fn setSoundCntX(self: *Self, value: bool) void {
+        self.cnt.apu_enable.write(value);
+    }
+
+    pub fn setSoundCntLLow(self: *Self, byte: u8) void {
+        self.ch_vol_cnt.raw = (self.ch_vol_cnt.raw & 0xFF00) | byte;
+    }
+
+    pub fn setBiasHigh(self: *Self, byte: u8) void {
+        self.bias.raw = (@as(u16, byte) << 8) | (self.bias.raw & 0xFF);
+    }
+};
+
+const ToneSweep = struct {
+    const Self = @This();
+
+    sweep: io.Sweep,
+    duty: io.Duty,
+    envelope: io.Envelope,
+    freq: io.Frequency,
+
+    fn init() Self {
+        return .{
+            .sweep = .{ .raw = 0 },
+            .duty = .{ .raw = 0 },
+            .envelope = .{ .raw = 0 },
+            .freq = .{ .raw = 0 },
+        };
+    }
+
+    pub fn setFreqHigh(self: *Self, byte: u8) void {
+        self.freq.raw = (@as(u16, byte) << 8) | (self.freq.raw & 0xFF);
+    }
+};
+
+const Tone = struct {
+    const Self = @This();
+
+    duty: io.Duty,
+    envelope: io.Envelope,
+    freq: io.Frequency,
+
+    fn init() Self {
+        return .{
+            .duty = .{ .raw = 0 },
+            .envelope = .{ .raw = 0 },
+            .freq = .{ .raw = 0 },
+        };
+    }
+
+    pub fn setFreqHigh(self: *Self, byte: u8) void {
+        self.freq.raw = (self.freq.raw & 0x00FF) | (@as(u16, byte) << 8);
+    }
+};
+
+const Wave = struct {
+    const Self = @This();
+
+    /// Write-only
+    select: io.WaveSelect,
+    /// NR31    
+    length: u8,
+    vol: io.WaveVolume,
+    freq: io.Frequency,
+
+    fn init() Self {
+        return .{
+            .select = .{ .raw = 0 },
+            .vol = .{ .raw = 0 },
+            .freq = .{ .raw = 0 },
+            .length = 0,
+        };
+    }
+};
+
+const Noise = struct {
+    const Self = @This();
+
+    /// Write-only
+    /// NR41
+    len: u6,
+    envelope: io.Envelope,
+    poly: io.PolyCounter,
+    cnt: io.NoiseControl,
+
+    fn init() Self {
+        return .{
+            .len = 0,
+            .envelope = .{ .raw = 0 },
+            .poly = .{ .raw = 0 },
+            .cnt = .{ .raw = 0 },
+        };
+    }
+};
+const DmaSound = struct {
+    const Self = @This();
+
+    a: SoundFifo,
+    b: SoundFifo,
+
+    fn init() Self {
+        return .{
+            .a = SoundFifo.init(),
+            .b = SoundFifo.init(),
+        };
+    }
+};