feat: define APU registers

src/Bus.zig

@@ -6,6 +6,7 @@ const GamePak = @import("bus/GamePak.zig");
 const Io = @import("bus/io.zig").Io;
 const Iwram = @import("bus/Iwram.zig");
 const Ppu = @import("ppu.zig").Ppu;
+const Apu = @import("apu.zig").Apu;
 const Scheduler = @import("scheduler.zig").Scheduler;
 
 const io = @import("bus/io.zig");
@@ -18,6 +19,7 @@ const panic_on_und_bus: bool = false;
 pak: GamePak,
 bios: Bios,
 ppu: Ppu,
+apu: Apu,
 iwram: Iwram,
 ewram: Ewram,
 io: Io,
@@ -27,6 +29,7 @@ pub fn init(alloc: Allocator, sched: *Scheduler, rom_path: []const u8, maybe_bio
         .pak = try GamePak.init(alloc, rom_path),
         .bios = try Bios.init(alloc, maybe_bios),
         .ppu = try Ppu.init(alloc, sched),
+        .apu = Apu.init(),
         .iwram = try Iwram.init(alloc),
         .ewram = try Ewram.init(alloc),
         .io = Io.init(sched),

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(),
+        };
+    }
+};

src/bus/io.zig

@@ -150,7 +150,7 @@ pub fn read16(bus: *const Bus, addr: u32) u16 {
         0x0400_0006 => bus.ppu.vcount.raw,
 
         // Sound
-        0x0400_0088 => unimplementedRead("Read halfword from SOUNDBIAS", .{}),
+        0x0400_0088 => bus.apu.bias.raw,
 
         // Timers
         0x0400_0100 => bus.io.tim0.counter(),
@@ -210,10 +210,10 @@ pub fn write16(bus: *Bus, addr: u32, halfword: u16) void {
         0x0400_0054 => log.warn("Wrote 0x{X:0>4} to BLDY", .{halfword}),
 
         // Sound
-        0x0400_0080 => log.warn("Wrote 0x{X:0>4} to SOUNDCNT_L", .{halfword}),
+        0x0400_0080 => bus.apu.ch_vol_cnt.raw = halfword,
-        0x0400_0082 => log.warn("Wrote 0x{X:0>4} to SOUNDCNT_H", .{halfword}),
+        0x0400_0082 => bus.apu.dma_cnt.raw = halfword,
-        0x0400_0084 => log.warn("Wrote 0x{X:0>4} to SOUNDCNT_X", .{halfword}),
+        0x0400_0084 => bus.apu.setSoundCntX(halfword >> 7 & 1 == 1),
-        0x0400_0088 => log.warn("Wrote 0x{X:0>4} to SOUNDBIAS", .{halfword}),
+        0x0400_0088 => bus.apu.bias.raw = halfword,
 
         // Dma Transfers
         0x0400_00B8 => bus.io.dma0.writeWordCount(halfword),
@@ -267,7 +267,7 @@ pub fn read8(bus: *const Bus, addr: u32) u8 {
         0x0400_0006 => @truncate(u8, bus.ppu.vcount.raw),
 
         // Sound
-        0x0400_0089 => unimplementedRead("Read (high) byte from SOUNDBIAS", .{}),
+        0x0400_0089 => @truncate(u8, bus.apu.bias.raw >> 8),
 
         // Serial Communication 1
         0x0400_0128 => unimplementedRead("Read (low) byte from SIOCNT", .{}),
@@ -279,23 +279,23 @@ pub fn read8(bus: *const Bus, addr: u32) u8 {
     };
 }
 
-pub fn write8(self: *Bus, addr: u32, byte: u8) void {
+pub fn write8(bus: *Bus, addr: u32, byte: u8) void {
     switch (addr) {
         // Display
-        0x0400_0004 => self.ppu.dispstat.raw = (self.ppu.dispstat.raw & 0xFF00) | byte,
+        0x0400_0004 => bus.ppu.dispstat.raw = (bus.ppu.dispstat.raw & 0xFF00) | byte,
-        0x0400_0005 => self.ppu.dispstat.raw = (@as(u16, byte) << 8) | (self.ppu.dispstat.raw & 0xFF),
+        0x0400_0005 => bus.ppu.dispstat.raw = (@as(u16, byte) << 8) | (bus.ppu.dispstat.raw & 0xFF),
 
         // Sound
-        0x0400_0063 => log.warn("Wrote 0x{X:0>2} to SOUND1CNT_H (high)", .{byte}),
+        0x0400_0063 => bus.apu.ch1.envelope.raw = byte,
-        0x0400_0065 => log.warn("Wrote 0x{X:0>2} to SOUND1CNT_X (high)", .{byte}),
+        0x0400_0065 => bus.apu.ch1.setFreqHigh(byte),
-        0x0400_0069 => log.warn("Wrote 0x{X:0>2} to SOUND2CNT_L (high)", .{byte}),
+        0x0400_0069 => bus.apu.ch2.envelope.raw = byte,
-        0x0400_006D => log.warn("Wrote 0x{X:0>2} to SOUND2CNT_H (high)", .{byte}),
+        0x0400_006D => bus.apu.ch2.setFreqHigh(byte),
-        0x0400_0070 => log.warn("Wrote 0x{X:0>2} to SOUND3CNT_L (low)", .{byte}),
+        0x0400_0070 => bus.apu.ch3.select.raw = byte,
-        0x0400_0079 => log.warn("Wrote 0x{X:0>2} to SOUND4CNT_L (high)", .{byte}),
+        0x0400_0079 => bus.apu.ch4.envelope.raw = byte,
-        0x0400_007D => log.warn("Wrote 0x{X:0>2} to SOUND4CNT_H (high)", .{byte}),
+        0x0400_007D => bus.apu.ch4.cnt.raw = byte,
-        0x0400_0080 => log.warn("Wrote 0x{X:0>2} to SOUNDCNT_L (low)", .{byte}),
+        0x0400_0080 => bus.apu.setSoundCntLLow(byte),
-        0x0400_0084 => log.warn("Wrote 0x{X:0>2} to SOUNDCNT_X (low)", .{byte}),
+        0x0400_0084 => bus.apu.setSoundCntX(byte >> 7 & 1 == 1),
-        0x0400_0089 => log.warn("Wrote 0x{X:0>2} to SOUNDBIAS (high)", .{byte}),
+        0x0400_0089 => bus.apu.setBiasHigh(byte),
 
         // Serial Communication 1
         0x0400_0128 => log.warn("Wrote 0x{X:0>2} to SIOCNT (low)", .{byte}),
@@ -304,8 +304,8 @@ pub fn write8(self: *Bus, addr: u32, byte: u8) void {
         0x0400_0140 => log.warn("Wrote 0x{X:0>2} to JOYCNT (low)", .{byte}),
 
         // Interrupts
-        0x0400_0208 => self.io.ime = byte & 1 == 1,
+        0x0400_0208 => bus.io.ime = byte & 1 == 1,
-        0x0400_0301 => self.io.haltcnt = if (byte >> 7 & 1 == 0) .Halt else std.debug.panic("TODO: Implement STOP", .{}),
+        0x0400_0301 => bus.io.haltcnt = if (byte >> 7 & 1 == 0) .Halt else std.debug.panic("TODO: Implement STOP", .{}),
         else => undWrite("Tried to write 0x{X:0>2} to 0x{X:0>8}", .{ byte, addr }),
     }
 }
@@ -462,3 +462,135 @@ pub const TimerControl = extern union {
     enabled: Bit(u16, 7),
     raw: u16,
 };
+
+/// Read / Write
+/// NR10
+pub const Sweep = extern union {
+    shift: Bitfield(u8, 0, 3),
+    direction: Bit(u8, 3),
+    period: Bitfield(u8, 4, 3),
+    raw: u8,
+};
+
+/// Read / Write
+/// This represents the Duty / Len
+/// NRx1
+pub const Duty = extern union {
+    /// Write-only
+    /// Only used when bit 6 is set
+    length: Bitfield(u16, 0, 6),
+    pattern: Bitfield(u16, 6, 2),
+    raw: u8,
+};
+
+/// Read / Write 
+/// NRx2
+pub const Envelope = extern union {
+    period: Bitfield(u8, 0, 3),
+    direction: Bit(u8, 3),
+    init_vol: Bitfield(u8, 4, 4),
+    raw: u8,
+};
+
+/// Read / Write
+/// NRx3, NRx4
+pub const Frequency = extern union {
+    /// Write-only
+    frequency: Bitfield(u16, 0, 11),
+    length_enable: Bit(u16, 14),
+    /// Write-only
+    trigger: Bit(u16, 15),
+
+    raw: u16,
+};
+
+/// Read / Write
+/// NR30
+pub const WaveSelect = extern union {
+    dimension: Bit(u8, 5),
+    bank: Bit(u8, 6),
+    enabled: Bit(u8, 7),
+    raw: u8,
+};
+
+/// Read / Write
+/// NR32
+pub const WaveVolume = extern union {
+    kind: Bitfield(u8, 5, 2),
+    force: Bit(u8, 7),
+    raw: u8,
+};
+
+/// Read / Write
+/// NR43
+pub const PolyCounter = extern union {
+    div_ratio: Bitfield(u8, 0, 3),
+    width: Bit(u8, 3),
+    shift: Bitfield(u8, 4, 4),
+    raw: u8,
+};
+
+/// Read / Write
+/// NR44
+pub const NoiseControl = extern union {
+    length_enable: Bit(u8, 6),
+    trigger: Bit(u8, 7),
+    raw: u8,
+};
+
+/// Read / Write
+pub const ChannelVolumeControl = extern union {
+    left_vol: Bitfield(u16, 0, 3),
+    right_vol: Bitfield(u16, 4, 3),
+
+    ch1_right: Bit(u16, 8),
+    ch2_right: Bit(u16, 9),
+    ch3_right: Bit(u16, 10),
+    ch4_right: Bit(u16, 11),
+    ch1_left: Bit(u16, 12),
+    ch2_left: Bit(u16, 13),
+    ch3_left: Bit(u16, 14),
+    ch4_left: Bit(u16, 15),
+    raw: u16,
+};
+
+/// Read / Write
+pub const DmaSoundControl = extern union {
+    ch_vol: Bitfield(u16, 0, 2),
+    sa_vol: Bit(u16, 2),
+    sb_vol: Bit(u16, 3),
+
+    sa_right_enable: Bit(u16, 8),
+    sa_left_enable: Bit(u16, 9),
+    sa_timer: Bit(u16, 10),
+    /// Write only?
+    sa_reset: Bit(u16, 11),
+
+    sb_right_enable: Bit(u16, 12),
+    sb_left_enable: Bit(u16, 13),
+    sb_timer: Bit(u16, 14),
+    /// Write only?
+    sb_reset: Bit(u16, 15),
+    raw: u16,
+};
+
+/// Read / Write
+pub const SoundControl = extern union {
+    /// Read-only
+    ch1_enable: Bit(u8, 0),
+    /// Read-only
+    ch2_enable: Bit(u8, 1),
+    /// Read-only
+    ch3_enable: Bit(u8, 2),
+    /// Read-only
+    ch4_enable: Bit(u8, 3),
+    apu_enable: Bit(u8, 7),
+    raw: u8,
+};
+
+/// Read / Write
+pub const SoundBias = extern union {
+    level: Bitfield(u16, 1, 9),
+    sampling_cycle: Bitfield(u16, 14, 2),
+    raw: u16,
+};

src/ppu.zig

@@ -3,12 +3,14 @@ const io = @import("bus/io.zig");
 
 const EventKind = @import("scheduler.zig").EventKind;
 const Scheduler = @import("scheduler.zig").Scheduler;
+const Arm7tdmi = @import("cpu.zig").Arm7tdmi;
 
 const Bit = @import("bitfield").Bit;
 const Bitfield = @import("bitfield").Bitfield;
 
 const Allocator = std.mem.Allocator;
 const log = std.log.scoped(.PPU);
+const pollBlankingDma = @import("bus/dma.zig").pollBlankingDma;
 
 pub const width = 240;
 pub const height = 160;
@@ -351,6 +353,59 @@ pub const Ppu = struct {
             },
         };
     }
+
+    pub fn handleHDrawEnd(self: *Self, cpu: *Arm7tdmi) void {
+        // Transitioning to a Hblank
+        if (self.dispstat.hblank_irq.read()) {
+            cpu.bus.io.irq.hblank.set();
+            cpu.handleInterrupt();
+        }
+
+        // See if HBlank DMA is present and not enabled
+        pollBlankingDma(cpu.bus, .HBlank);
+
+        self.dispstat.hblank.set();
+        self.sched.push(.HBlank, self.sched.now() + (68 * 4));
+    }
+
+    pub fn handleHBlankEnd(self: *Self, cpu: *Arm7tdmi) void {
+        // The End of a Hblank (During Draw or Vblank)
+        const old_scanline = self.vcount.scanline.read();
+        const scanline = (old_scanline + 1) % 228;
+
+        self.vcount.scanline.write(scanline);
+        self.dispstat.hblank.unset();
+
+        // Perform Vc == VcT check
+        const coincidence = scanline == self.dispstat.vcount_trigger.read();
+        self.dispstat.coincidence.write(coincidence);
+
+        if (coincidence and self.dispstat.vcount_irq.read()) {
+            cpu.bus.io.irq.coincidence.set();
+            cpu.handleInterrupt();
+        }
+
+        if (scanline < 160) {
+            // Transitioning to another Draw
+            self.sched.push(.Draw, self.sched.now() + (240 * 4));
+        } else {
+            // Transitioning to a Vblank
+            if (scanline == 160) {
+                self.dispstat.vblank.set();
+
+                if (self.dispstat.vblank_irq.read()) {
+                    cpu.bus.io.irq.vblank.set();
+                    cpu.handleInterrupt();
+                }
+
+                // See if Vblank DMA is present and not enabled
+                pollBlankingDma(cpu.bus, .VBlank);
+            }
+
+            if (scanline == 227) self.dispstat.vblank.unset();
+            self.sched.push(.VBlank, self.sched.now() + (240 * 4));
+        }
+    }
 };
 
 const Palette = struct {

src/scheduler.zig

@@ -1,7 +1,5 @@
 const std = @import("std");
 
-const pollBlankingDma = @import("bus/dma.zig").pollBlankingDma;
-
 const Bus = @import("Bus.zig");
 const Arm7tdmi = @import("cpu.zig").Arm7tdmi;
 
@@ -32,92 +30,18 @@ pub const Scheduler = struct {
     }
 
     pub fn handleEvent(self: *Self, cpu: *Arm7tdmi, bus: *Bus) void {
-        const should_handle = if (self.queue.peek()) |e| self.tick >= e.tick else false;
+        if (self.queue.removeOrNull()) |event| {
-        const stat = &bus.ppu.dispstat;
-        const vcount = &bus.ppu.vcount;
-        const irq = &bus.io.irq;
-
-        if (should_handle) {
-            const event = self.queue.remove();
-            // log.debug("Handle {} @ tick = {}", .{ event.kind, self.tick });
-
             switch (event.kind) {
                 .HeatDeath => {
                     log.err("A u64 overflowered. This *actually* should never happen.", .{});
                     unreachable;
                 },
-                .HBlank => {
-                    // The End of a Hblank (During Draw or Vblank)
-                    const old_scanline = vcount.scanline.read();
-                    const scanline = (old_scanline + 1) % 228;
-
-                    vcount.scanline.write(scanline);
-                    stat.hblank.unset();
-
-                    // Perform Vc == VcT check
-                    const coincidence = scanline == stat.vcount_trigger.read();
-                    stat.coincidence.write(coincidence);
-
-                    if (coincidence and stat.vcount_irq.read()) {
-                        irq.coincidence.set();
-                        cpu.handleInterrupt();
-                    }
-
-                    if (scanline < 160) {
-                        // Transitioning to another Draw
-                        self.push(.Draw, self.tick + (240 * 4));
-                    } else {
-                        // Transitioning to a Vblank
-                        if (scanline == 160) {
-                            stat.vblank.set();
-
-                            if (stat.vblank_irq.read()) {
-                                irq.vblank.set();
-                                cpu.handleInterrupt();
-                            }
-
-                            // See if Vblank DMA is present and not enabled
-                            pollBlankingDma(bus, .VBlank);
-                        }
-
-                        if (scanline == 227) stat.vblank.unset();
-                        self.push(.VBlank, self.tick + (240 * 4));
-                    }
-                },
                 .Draw => {
-                    // The end of a Draw
+                    // The end of a VDraw
                     bus.ppu.drawScanline();
-
+                    bus.ppu.handleHDrawEnd(cpu);
-                    // Transitioning to a Hblank
-                    if (bus.ppu.dispstat.hblank_irq.read()) {
-                        bus.io.irq.hblank.set();
-                        cpu.handleInterrupt();
-                    }
-
-                    // See if Hblank DMA is present and not enabled
-                    pollBlankingDma(bus, .HBlank);
-
-                    bus.ppu.dispstat.hblank.set();
-                    self.push(.HBlank, self.tick + (68 * 4));
-                },
-                .VBlank => {
-                    // The end of a Vblank
-
-                    // Transitioning to a Hblank
-                    if (bus.ppu.dispstat.hblank_irq.read()) {
-                        bus.io.irq.hblank.set();
-                        cpu.handleInterrupt();
-                    }
-
-                    // See if Hblank DMA is present and not enabled
-                    pollBlankingDma(bus, .HBlank);
-
-                    bus.ppu.dispstat.hblank.set();
-                    self.push(.HBlank, self.tick + (68 * 4));
                 },
                 .TimerOverflow => |id| {
-                    // log.warn("TIM{} Overflowed", .{id});
-
                     switch (id) {
                         0 => bus.io.tim0.handleOverflow(cpu, &bus.io),
                         1 => bus.io.tim1.handleOverflow(cpu, &bus.io),
@@ -125,6 +49,8 @@ pub const Scheduler = struct {
                         3 => bus.io.tim3.handleOverflow(cpu, &bus.io),
                     }
                 },
+                .HBlank => bus.ppu.handleHBlankEnd(cpu), // The end of a HBlank
+                .VBlank => bus.ppu.handleHDrawEnd(cpu), // The end of a VBlank
             }
         }
     }
@@ -153,9 +79,9 @@ pub const Scheduler = struct {
     }
 
     pub fn nextTimestamp(self: *Self) u64 {
-        if (self.queue.peek()) |e| {
+        if (self.queue.peek()) |e| return e.tick;
-            return e.tick;
+
-        } else unreachable;
+        unreachable; // There's always the HeatDeath event scheduled
     }
 };