feat: add option to force-enable RTC

src/core/bus/GamePak.zig

@@ -6,6 +6,8 @@ const Bit = @import("bitfield").Bit;
 const Bitfield = @import("bitfield").Bitfield;
 const Backup = @import("backup.zig").Backup;
 const Allocator = std.mem.Allocator;
+
+const force_rtc = @import("../emu.zig").force_rtc;
 const log = std.log.scoped(.GamePak);
 
 const Self = @This();
@@ -22,7 +24,9 @@ pub fn init(allocator: Allocator, cpu: *Arm7tdmi, rom_path: []const u8, save_pat
 
     const file_buf = try file.readToEndAlloc(allocator, try file.getEndPos());
     const title = file_buf[0xA0..0xAC].*;
-    const kind = Backup.guessKind(file_buf) orelse .None;
+    const kind = Backup.guessKind(file_buf);
+    const device = if (force_rtc) .Rtc else guessDevice(file_buf);
+
     logHeader(file_buf, &title);
 
     return .{
@@ -30,10 +34,26 @@ pub fn init(allocator: Allocator, cpu: *Arm7tdmi, rom_path: []const u8, save_pat
         .allocator = allocator,
         .title = title,
         .backup = try Backup.init(allocator, kind, title, save_path),
-        .gpio = try Gpio.init(allocator, cpu, .Rtc),
+        .gpio = try Gpio.init(allocator, cpu, device),
     };
 }
 
+/// Searches the ROM to see if it can determine whether the ROM it's searching uses
+/// any GPIO device, like a RTC for example.
+fn guessDevice(buf: []const u8) Gpio.Device.Kind {
+    // Try to Guess if ROM uses RTC
+    const needle = "RTC_V"; // I was told SIIRTC_V, though Pokemen Firered (USA) is a false negative
+
+    var i: usize = 0;
+    while ((i + needle.len) < buf.len) : (i += 1) {
+        if (std.mem.eql(u8, needle, buf[i..(i + needle.len)])) return .Rtc;
+    }
+
+    // TODO: Detect other GPIO devices
+
+    return .None;
+}
+
 fn logHeader(buf: []const u8, title: *const [12]u8) void {
     const code = buf[0xAC..0xB0];
     const maker = buf[0xB0..0xB2];
@@ -258,8 +278,9 @@ const Gpio = struct {
     };
 
     fn init(allocator: Allocator, cpu: *Arm7tdmi, kind: Device.Kind) !*This {
-        const self = try allocator.create(This);
+        log.info("Device: {}", .{kind});
 
+        const self = try allocator.create(This);
         self.* = .{
             .data = 0b0000,
             .direction = 0b1111, // TODO: What is GPIO DIrection set to by default?
@@ -505,8 +526,8 @@ pub const Clock = struct {
         cpu.sched.push(.RealTimeClock, 1 << 24); // Every Second
     }
 
-    pub fn updateTime(self: *This) void {
+    pub fn updateTime(self: *This, late: u64) void {
-        self.cpu.sched.push(.RealTimeClock, 1 << 24); // Reschedule
+        self.cpu.sched.push(.RealTimeClock, (1 << 24) -| late); // Reschedule
 
         const now = DateTime.now();
         self.year = toBcd(u8, @intCast(u8, now.date.year - 2000));

src/core/bus/backup.zig

@@ -61,7 +61,7 @@ pub const Backup = struct {
         return backup;
     }
 
-    pub fn guessKind(rom: []const u8) ?Kind {
+    pub fn guessKind(rom: []const u8) Kind {
         for (backup_kinds) |needle| {
             const needle_len = needle.str.len;
 
@@ -71,7 +71,7 @@ pub const Backup = struct {
             }
         }
 
-        return null;
+        return .None;
     }
 
     pub fn deinit(self: *Self) void {

src/core/emu.zig

@@ -18,6 +18,7 @@ const sync_video: RunKind = .LimitedFPS; // Configure Video Sync
 pub const win_scale = 3; // 1x, 2x, 3x, etc. Window Scaling
 pub const cpu_logging = false; // Enable detailed CPU logging
 pub const allow_unhandled_io = true; // Only relevant in Debug Builds
+pub const force_rtc = false;
 
 // 228 Lines which consist of 308 dots (which are 4 cycles long)
 const cycles_per_frame: u64 = 228 * (308 * 4); //280896

src/core/scheduler.zig

@@ -66,7 +66,7 @@ pub const Scheduler = struct {
                     if (device.kind != .Rtc or device.ptr == null) return;
 
                     const clock = @ptrCast(*Clock, @alignCast(@alignOf(*Clock), device.ptr.?));
-                    clock.updateTime();
+                    clock.updateTime(late);
                 },
                 .FrameSequencer => cpu.bus.apu.tickFrameSequencer(late),
                 .SampleAudio => cpu.bus.apu.sampleAudio(late),