minor code cleanup, start with audio beeper

src/chips/ay3891.zig

@@ -42,15 +42,15 @@ pub const Model = enum {
     AY38913, // no IO ports
 };
 
-pub const Config = struct {
+pub const TypeConfig = struct {
     model: Model = .AY38910,
     pins: Pins,
     bus: type,
     dcadjust_buf_len: u32 = 128,
     enable_lowpass_filter: bool = true,
 };
 
-pub fn Type(comptime cfg: Config) type {
+pub fn Type(comptime cfg: TypeConfig) type {
     return struct {
         const Self = @This();
         const Bus = cfg.bus;
@@ -177,7 +177,7 @@ pub fn Type(comptime cfg: Config) type {
             period: i32 = 0,
             counter: i32 = 0,
             volume: f32 = 0.0,
-            value: f32 = 0.0,
+            out: f32 = 0.0, // output sample value
             ready: bool = false, // true if a new sample value is ready
             filter: filter.Type(.{
                 .enable_dcadjust = true,
@@ -186,7 +186,7 @@ pub fn Type(comptime cfg: Config) type {
             }) = .{},
         };
 
-        tick_count: u38 = 0, // tick counter for internal clock division
+        tick_count: u32 = 0, // tick counter for internal clock division
         cs_mask: u8 = 0, // hi: 4-bit chip-select (options.chip_select << 4)
         active: bool = false, // true if upper chip-select matches when writing address
         addr: u4 = 0, // current register index
@@ -329,6 +329,7 @@ pub fn Type(comptime cfg: Config) type {
                 self.env.shape.state = env_shapes[self.regs[REG.ENV_SHAPE_CYCLE]][self.env.shape.counter];
             }
 
+            // FIXME: add some oversampling for anti-aliasing(?)
             // generate sample
             self.sample.counter -= FIXEDPOINT_SCALE;
             if (self.sample.counter <= 0) {
@@ -348,7 +349,7 @@ pub fn Type(comptime cfg: Config) type {
                         }
                     }
                 }
-                self.sample.value = self.sample.filter.put(sm) * self.sample.volume;
+                self.sample.out = self.sample.filter.put(sm) * self.sample.volume;
                 self.sample.ready = true;
             } else {
                 self.sample.ready = false;

src/chips/z80.zig

@@ -62,12 +62,12 @@ const indirect_table = init: {
 };
 // zig fmt: on
 
-pub const Config = struct {
+pub const TypeConfig = struct {
     pins: Pins,
     bus: type,
 };
 
-pub fn Type(comptime cfg: Config) type {
+pub fn Type(comptime cfg: TypeConfig) type {
     const Bus = cfg.bus;
     return struct {
         const Self = @This();

src/chips/z80ctc.zig

@@ -37,9 +37,9 @@ pub const DefaultPins = Pins{
     .IEIO = 23,
 };
 
-pub const Config = struct { pins: Pins, bus: type };
+pub const TypeConfig = struct { pins: Pins, bus: type };
 
-pub fn Type(comptime cfg: Config) type {
+pub fn Type(comptime cfg: TypeConfig) type {
     assert(cfg.pins.CS[1] == cfg.pins.CS[0] + 1);
     assert(cfg.pins.ZCTO[1] == cfg.pins.ZCTO[0] + 1);
     assert(cfg.pins.ZCTO[2] == cfg.pins.ZCTO[1] + 1);

src/chips/z80irq.zig

@@ -12,12 +12,12 @@ pub const Pins = struct {
     IEIO: comptime_int,
 };
 
-pub const Config = struct {
+pub const TypeConfig = struct {
     pins: Pins,
     bus: type,
 };
 
-pub fn Type(comptime cfg: Config) type {
+pub fn Type(comptime cfg: TypeConfig) type {
     const Bus = cfg.bus;
     return struct {
         const Self = @This();

src/chips/z80pio.zig

@@ -45,12 +45,12 @@ pub const DefaultPins = Pins{
     .IEIO = 36,
 };
 
-pub const Config = struct {
+pub const TypeConfig = struct {
     pins: Pins,
     bus: type,
 };
 
-pub fn Type(cfg: Config) type {
+pub fn Type(cfg: TypeConfig) type {
     const Bus = cfg.bus;
     const Z80IRQ = z80irq.Type(.{
         .pins = .{

src/common/beeper.zig

@@ -0,0 +1,61 @@
+//! a simple square wave beeper sound device
+const filter = @import("filter.zig");
+
+pub const TypeConfig = struct {
+    dcadjust_buf_len: u32 = 128,
+    enable_lowpass_filter: bool = true,
+};
+
+pub fn Type(comptime cfg: TypeConfig) type {
+    return struct {
+        const Self = @This();
+
+        pub const Options = struct {
+            tick_hz: u32,
+            sound_hz: u32,
+            base_volume: f32 = 1.0,
+        };
+
+        const OVERSAMPLE = 8; // anti-aliasing oversampling
+        const FIXEDPOINT_SCALE = 16; // error-reduction for sample period counter
+
+        state: u1 = 0,
+        period: i32 = 0,
+        counter: i32 = 0,
+        base_volume: f32 = 1.0,
+        volume: f32 = 1.0,
+        sample: struct {
+            ready: bool = false,
+            out: f32 = 0.0,
+            accum: f32 = 0.0, // oversampling accumulator for anti-aliasing
+            div: f32 = 0.0, // oversampling divider
+        },
+        filter: filter.Type(.{
+            .enable_dcadjust = true,
+            .enable_lowpass_filter = cfg.enable_lowpass_filter,
+            .dcadjust_buf_len = cfg.dcadjust_buf_len,
+        }),
+
+        pub fn init(opts: Options) Self {
+            _ = opts; // autofix
+            // FIXME
+        }
+
+        pub fn setVolume(self: *Self, v: f32) void {
+            self.volume = v;
+        }
+
+        pub fn toggle(self: *Self) void {
+            self.state ^= 1;
+        }
+
+        pub fn set(self: *Self, state: u1) void {
+            self.state = state;
+        }
+
+        pub fn tick(self: *Self) bool {
+            _ = self; // autofix
+            return false;
+        }
+    };
+}

src/common/filter.zig

@@ -4,13 +4,13 @@ const std = @import("std");
 const assert = std.debug.assert;
 const isPowerOfTwo = std.math.isPowerOfTwo;
 
-pub const Config = struct {
+pub const TypeConfig = struct {
     enable_dcadjust: bool,
     enable_lowpass_filter: bool,
     dcadjust_buf_len: u32,
 };
 
-pub fn Type(cfg: Config) type {
+pub fn Type(cfg: TypeConfig) type {
     assert(isPowerOfTwo(cfg.dcadjust_buf_len));
     return struct {
         const Self = @This();

src/common/memory.zig

@@ -21,11 +21,11 @@ pub const Page = struct {
     write: [*]u8,
 };
 
-pub const Config = struct {
+pub const TypeConfig = struct {
     page_size: comptime_int,
 };
 
-pub fn Type(comptime cfg: Config) type {
+pub fn Type(comptime cfg: TypeConfig) type {
     assert(std.math.isPowerOfTwo(cfg.page_size));
 
     return struct {

src/systems/bombjack.zig

@@ -532,7 +532,7 @@ pub const Bombjack = struct {
             bus &= ~(PSG0.BDIR | PSG0.BC1 | PSG1.BDIR | PSG1.BC1 | PSG2.BDIR | PSG2.BC1);
 
             if (board.psg0.sample.ready) {
-                const s = board.psg0.sample.value + board.psg1.sample.value + board.psg2.sample.value;
+                const s = board.psg0.sample.out + board.psg1.sample.out + board.psg2.sample.out;
                 self.audio.sample_buffer[self.audio.sample_pos] = s * self.audio.volume;
                 self.audio.sample_pos += 1;
                 if (self.audio.sample_pos == self.audio.num_samples) {