Update readme

README.md

@@ -7,12 +7,23 @@ Any help or suggestion is welcome!
 
 ## TODO
 - [x] CPU implementation
-- [x] Interrupts (interrupts test not passing yet)
+- [x] Interrupts
 - [x] Timer
 - [x] Joypad (not configurable yet)
-- [ ] PPU implementations
-- [ ] Gameboy boot ROM
+- [X] PPU implementations
 - [x] Render the pixels
+- [ ] MBC Implementations
+  - [x] NoMBC
+  - [ ] MBC1
+  - [ ] MBC2
+  - [ ] MBC3
+  - [ ] MBC4
+  - [ ] MBC5
+  - [ ] MBC6
+  - [ ] MBC7
+  - [ ] HuC1
+- [ ] Web Assembly support (because this is a Rust project and it has to support Web Assembly)
+- [ ] Gameboy boot ROM (Not important for now)
 - [ ] Gameboy Color compatibility
 - [ ] Sound
-- [ ] Web Assembly support (because this is a Rust project and it has to support Web Assembly)
+- [ ] Many code refactors and optimizations are needed

src/bus.rs

@@ -57,7 +57,7 @@ pub struct Bus {
 
 impl Bus {
     pub fn new() -> Self {
-        let game_rom = match ROM::load_file("ignore/tetris.gb".to_string()) {
+        let game_rom = match ROM::load_file("ignore/dmg-acid2.gb".to_string()) {
         // let game_rom = match ROM::load_file("ignore/mooneye/emulator-only/mbc1/bits_bank1.gb".to_string()) {
         // let game_rom = match ROM::load_file("roms/cpu_instrs.gb".to_string()) {
         // let game_rom = match ROM::load_file("roms/cpu_instrs_individual/01-special.gb".to_string()) {
@@ -129,7 +129,6 @@ impl Bus {
 
         if BANK_ZERO.in_range(address) || BANK_SWITCHABLE.in_range(address) || EXTERNAL_RAM.in_range(address) {
             self.game_rom.write(address, data);
-            // println!("WRITING TO ROM");
         } else if WORK_RAM_1.in_range(address) || WORK_RAM_2.in_range(address) {
             self.data[address as usize] = data;
             // Copy to the ECHO RAM
@@ -143,9 +142,12 @@ impl Bus {
             self.data[(WORK_RAM_1.begin() + (address - ECHO_RAM.begin())) as usize] = data; // Copy to the working RAM
         } else if address == TIMER_DIVIDER_REGISTER_ADDRESS {
             self.reset_timer = true;
-        } else if address == LCD_CONTROL_ADDRESS && get_bit(data, BitIndex::I7) {
+        } else if address == LCD_CONTROL_ADDRESS {
             self.data[address as usize] = data;
-            self.data[LCD_Y_ADDRESS as usize] = 0x00;
+            // Check if LCD is being turned on 
+            if get_bit(data, BitIndex::I7) && !get_bit(self.data[address as usize], BitIndex::I7) {
+                self.data[LCD_Y_ADDRESS as usize] = 0x00;
+            }
         } else if address == LCD_Y_ADDRESS {
             // println!("Write to LCD_Y not allowed");
         } else if address == LCD_STATUS_ADDRESS {

src/ppu.rs

@@ -23,8 +23,8 @@ pub const DMA_ADDRESS: u16 = 0xFF46;
 pub const BACKGROUND_PALETTE_ADDRESS: u16 = 0xFF47;
 pub const OBJECT_PALETTE_0_ADDRESS: u16 = 0xFF48;
 pub const OBJECT_PALETTE_1_ADDRESS: u16 = 0xFF49;
-pub const WINDOW_X_ADDRESS: u16 = 0xFF4A;
-pub const WINDOW_Y_ADDRESS: u16 = 0xFF4B;
+pub const WINDOW_X_ADDRESS: u16 = 0xFF4B;
+pub const WINDOW_Y_ADDRESS: u16 = 0xFF4A;
 pub const TILE_MAP_ADDRESS: u16 = 0x9800;
 
 #[derive(Debug, Copy, Clone)]
@@ -89,12 +89,6 @@ pub enum LCDStatus {
     ModeFlag(LCDStatusModeFlag),
 }
 
-pub struct PPU {
-    prev_state: bool,
-    cycles: Cycles,
-    sprite_buffer: Vec<Sprite>,
-}
-
 struct Sprite {
     x: u8,
     y: u8,
@@ -111,13 +105,13 @@ impl Sprite {
         self.x
     }
 
-    pub fn get_pixel(&self, lcd_x: u8, lcd_y: u8, bus: &Bus) -> Option<Pixel> {
+    pub fn get_pixel(&self, lcd_x: u8, lcd_y: u8, bus: &Bus, last_bg_index: u8) -> Option<Pixel> {
         if lcd_x < self.x.saturating_sub(8) || lcd_x >= self.x {
             return None;
         }
 
-        if self.over_bg {
-            // todo!("Implement over_bg sprite property");
+        if self.over_bg && (last_bg_index & 0b11) != 0 {
+            return None;
         }
 
         let height: u8 = match self.is_long {
@@ -151,9 +145,11 @@ impl Sprite {
         let tile_byte_1 = bus.read(addr);
         let tile_byte_2 = bus.read(addr + 1);
 
-        let pixel_index = (x as usize).rem_euclid(8);
+        let pixels = PPU::get_byte_pixels(tile_byte_1, tile_byte_2);
 
-        if PPU::get_two_bit_byte_pixels(tile_byte_1, tile_byte_2)[pixel_index] == 0 {
+        let index = (x as usize).rem_euclid(8);
+
+        if pixels[index] == 0 {
             return None;
         }
 
@@ -161,19 +157,26 @@ impl Sprite {
             true => bus.read(OBJECT_PALETTE_1_ADDRESS),
             false => bus.read(OBJECT_PALETTE_0_ADDRESS),
         };
-        let pixels = PPU::get_byte_pixels(tile_byte_1, tile_byte_2, palette);
-
-        Some(pixels[pixel_index])
-
+        Some(PPU::get_pixel(PPU::get_palette(pixels[index], palette)))
     }
 }
 
+pub struct PPU {
+    state: bool,
+    cycles: Cycles,
+    sprite_buffer: Vec<Sprite>,
+    window_y_counter: u8,
+    last_bg_index: u8,
+}
+
 impl PPU {
     pub fn new() -> Self {
         Self {
-            prev_state: false,
+            state: false,
             cycles: Cycles(0),
             sprite_buffer: Vec::new(),
+            window_y_counter: 0,
+            last_bg_index: 0,
         }
     }
 
@@ -199,8 +202,8 @@ impl PPU {
                 self.oam_search(bus);
             } else if self.cycles.0 > 80 && self.cycles.0 <= 80 + 172 && !PPU::get_lcd_status(bus, LCDStatus::ModeFlag(LCDStatusModeFlag::TransferringToLCD)) {
                 // Mode 3 drawing pixel line. This could also last 289 cycles
-                self.draw_line(bus, frame_buffer);
                 PPU::set_lcd_status(bus, LCDStatus::ModeFlag(LCDStatusModeFlag::TransferringToLCD), true);
+                self.draw_line(bus, frame_buffer);
             } else if self.cycles.0 > 80 + 172 && self.cycles.0 <= 80 + 172 + 204 && !PPU::get_lcd_status(bus, LCDStatus::ModeFlag(LCDStatusModeFlag::HBlank)) {
                 // Mode 0 Horizontal blank. This could last 87 or 204 cycles depending on the mode 3
                 PPU::set_lcd_status(bus, LCDStatus::ModeFlag(LCDStatusModeFlag::HBlank), true);
@@ -208,8 +211,8 @@ impl PPU {
             }
         } else if PPU::get_lcd_y(bus) >= 144 && !PPU::get_lcd_status(bus, LCDStatus::ModeFlag(LCDStatusModeFlag::VBlank)) {
             // Mode 1 Vertical blank
-            bus.set_interrupt_flag(Interrupt::VBlank, true);
             PPU::set_lcd_status(bus, LCDStatus::ModeFlag(LCDStatusModeFlag::VBlank), true);
+            bus.set_interrupt_flag(Interrupt::VBlank, true);
             self.stat_interrupt(bus);
         }
 
@@ -220,30 +223,47 @@ impl PPU {
             self.reset_cycles();
 
             PPU::set_lcd_y(bus, PPU::get_lcd_y(bus).wrapping_add(1));
+
             // Frame completed
             if PPU::get_lcd_y(bus) > 153 {
                 PPU::set_lcd_y(bus, 0);
+                self.window_y_counter = 0;
             }
-            self.check_lyc(bus);
+            // self.check_lyc(bus);
+            self.stat_interrupt(bus);
         }
     }
 
     fn stat_interrupt(&mut self, bus: &mut Bus) {
-        let state = self.prev_state;
-        self.prev_state = (PPU::get_lcd_status(bus, LCDStatus::Mode2OAMInterrupt)    && PPU::get_lcd_status(bus, LCDStatus::ModeFlag(LCDStatusModeFlag::SearchingOAM))) ||
-            (PPU::get_lcd_status(bus, LCDStatus::Mode0HBlankInterrupt) && PPU::get_lcd_status(bus, LCDStatus::ModeFlag(LCDStatusModeFlag::HBlank))) ||
-            (PPU::get_lcd_status(bus, LCDStatus::Mode1VBlankInterrupt) && PPU::get_lcd_status(bus, LCDStatus::ModeFlag(LCDStatusModeFlag::VBlank)));
-        if self.prev_state && !state {
-            bus.set_interrupt_flag(Interrupt::LCDSTAT, true);
+        let prev_state = self.state;
+        let lyc_compare = PPU::get_lcd_y(bus) == bus.read(LCD_Y_COMPARE_ADDRESS);
+        PPU::set_lcd_status(bus, LCDStatus::LYCFlag, lyc_compare);
+        self.state =
+            (
+                lyc_compare &&
+                PPU::get_lcd_status(bus, LCDStatus::LYCInterrupt)
+            ) ||
+            (
+                PPU::get_lcd_status(bus, LCDStatus::Mode2OAMInterrupt) &&
+                PPU::get_lcd_status(bus, LCDStatus::ModeFlag(LCDStatusModeFlag::SearchingOAM))
+            ) || (
+                PPU::get_lcd_status(bus, LCDStatus::Mode0HBlankInterrupt) &&
+                PPU::get_lcd_status(bus, LCDStatus::ModeFlag(LCDStatusModeFlag::HBlank))
+            ) || (
+                PPU::get_lcd_status(bus, LCDStatus::Mode1VBlankInterrupt) &&
+                PPU::get_lcd_status(bus, LCDStatus::ModeFlag(LCDStatusModeFlag::VBlank))
+            );
+        if self.state && !prev_state {
+            bus.set_interrupt_flag(Interrupt::LCDSTAT, self.state);
         }
     }
 
     fn check_lyc(&mut self, bus: &mut Bus) {
         let lyc_compare = PPU::get_lcd_y(bus) == bus.read(LCD_Y_COMPARE_ADDRESS);
         PPU::set_lcd_status(bus, LCDStatus::LYCFlag, lyc_compare);
-        if lyc_compare && PPU::get_lcd_status(bus, LCDStatus::LYCInterrupt) {
+        if !self.state && lyc_compare && PPU::get_lcd_status(bus, LCDStatus::LYCInterrupt) {
             bus.set_interrupt_flag(Interrupt::LCDSTAT, true);
-            self.prev_state = true;
+            self.state = true;
         }
     }
 
@@ -259,7 +279,7 @@ impl PPU {
             // but since we are on an emulator we can avoud that limitation
             if self.sprite_buffer.len() >= 10 {
                 // todo!("Make a setting for the 10 sprites per scanline");
-                // break;
+                break;
             }
             let y = bus.read(addr);
             let x = bus.read(addr + 1);
@@ -304,7 +324,7 @@ impl PPU {
     fn find_sprite_pixel(&self, lcd_x: u8, bus: &Bus) -> Option<Pixel> {
         let lcd_y = PPU::get_lcd_y(bus);
         for sprite in &self.sprite_buffer {
-            if let Some(pixel) = sprite.get_pixel(lcd_x, lcd_y, bus) {
+            if let Some(pixel) = sprite.get_pixel(lcd_x, lcd_y, bus, self.last_bg_index) {
                 return Some(pixel);
             }
         }
@@ -394,17 +414,23 @@ impl PPU {
         (bus.read(addr), bus.read(addr + 1))
     }
 
-    fn get_window_pixel(lcd_x: u8, bus: &Bus) -> Option<Pixel> {
+    fn get_window_pixel(&mut self, lcd_x: u8, bus: &Bus) -> Option<Pixel> {
         let lcd_y = PPU::get_lcd_y(bus);
         let window_x = PPU::get_window_x(bus);
         let window_y = PPU::get_window_y(bus);
 
-        if !PPU::get_lcd_control(bus, LCDControl::WindowEnable) || lcd_x < (window_x.saturating_sub(7)) || window_y != lcd_y {
+        if
+            !PPU::get_lcd_control(bus, LCDControl::WindowEnable) ||
+            lcd_x < window_x.saturating_sub(7) ||
+            lcd_y < window_y ||
+            window_y >= 144 ||
+            window_x.saturating_sub(7) >= 160
+        {
             return None;
         }
 
         let x = lcd_x.wrapping_sub(window_x.saturating_sub(7));
-        let y = lcd_y.wrapping_sub(window_y);
+        let y = self.window_y_counter;
 
         let default_mode = PPU::get_lcd_control(bus, LCDControl::TileAddressMode);
         let tilemap_area = match PPU::get_lcd_control(bus, LCDControl::WindowTileMapAddress) {
@@ -414,44 +440,59 @@ impl PPU {
         let (tile_byte_1, tile_byte_2) = PPU::get_tile_bytes(x, y, tilemap_area, default_mode, bus);
 
         let palette = bus.read(BACKGROUND_PALETTE_ADDRESS);
-        let pixels = PPU::get_byte_pixels(tile_byte_1, tile_byte_2, palette);
+        let pixels = PPU::get_byte_pixels(tile_byte_1, tile_byte_2);
+        let index = pixels[(x as usize).rem_euclid(8)];
+        self.last_bg_index = index & 0b11;
 
-        Some(pixels[(x as usize).rem_euclid(8)])
+        Some(PPU::get_pixel(PPU::get_palette(index, palette)))
+    }
+
+    fn get_background_pixel(&mut self, lcd_x: u8, bus: &Bus) -> Option<Pixel> {
+        if !PPU::get_lcd_control(bus, LCDControl::BackgroundPriority) {
+            return None;
+        }
+        let lcd_y = PPU::get_lcd_y(bus);
+        let palette = bus.read(BACKGROUND_PALETTE_ADDRESS);
+        let y = lcd_y.wrapping_add(PPU::get_scroll_y(bus));
+        let x = lcd_x.wrapping_add(PPU::get_scroll_x(bus));
+
+        let default_mode = PPU::get_lcd_control(bus, LCDControl::TileAddressMode);
+        let tilemap_area = match PPU::get_lcd_control(bus, LCDControl::BackgroundTileMapAddress) {
+            true  => 0x9C00,
+            false => 0x9800,
+        };
+        let (tile_byte_1, tile_byte_2) = PPU::get_tile_bytes(x, y, tilemap_area, default_mode, bus);
+
+        let bg_pixels = PPU::get_byte_pixels(tile_byte_1, tile_byte_2);
+        let index = bg_pixels[x.rem_euclid(8) as usize];
+        self.last_bg_index = index & 0b11;
+
+        Some(PPU::get_pixel(PPU::get_palette(index, palette)))
     }
 
     fn draw_line(&mut self, bus: &Bus, frame_buffer: &mut [u8]) {
-        let palette = bus.read(BACKGROUND_PALETTE_ADDRESS);
         let lcd_y = PPU::get_lcd_y(bus);
         if lcd_y as u32 >= LCD_HEIGHT {
             return;
         }
         let mut lcd_x: u8 = 0;
+        let mut window_drawn = false;
         while (lcd_x as u32) < LCD_WIDTH {
-            let y = lcd_y.wrapping_add(PPU::get_scroll_y(bus));
-            let x = lcd_x.wrapping_add(PPU::get_scroll_x(bus));
-
-            let default_mode = PPU::get_lcd_control(bus, LCDControl::TileAddressMode);
-            let tilemap_area = match PPU::get_lcd_control(bus, LCDControl::BackgroundTileMapAddress) {
-                true  => 0x9C00,
-                false => 0x9800,
-            };
-            let (tile_byte_1, tile_byte_2) = PPU::get_tile_bytes(x, y, tilemap_area, default_mode, bus);
-
-            let bg_pixels = PPU::get_byte_pixels(tile_byte_1, tile_byte_2, palette);
-
             let idx = (lcd_x as usize + (lcd_y as usize * LCD_WIDTH as usize)) * 4;
-            let pixel = bg_pixels[x.rem_euclid(8) as usize];
-            let rgba = PPU::get_rgba(pixel);
-            frame_buffer[idx]     = rgba[0];
-            frame_buffer[idx + 1] = rgba[1];
-            frame_buffer[idx + 2] = rgba[2];
-            if let Some(window_pixel) = PPU::get_window_pixel(lcd_x, bus) {
+
+            if let Some(background_pixel) = self.get_background_pixel(lcd_x, bus) {
+                let rgba = PPU::get_rgba(background_pixel);
+                frame_buffer[idx]     = rgba[0];
+                frame_buffer[idx + 1] = rgba[1];
+                frame_buffer[idx + 2] = rgba[2];
+            }
+            if let Some(window_pixel) = self.get_window_pixel(lcd_x, bus) {
+                window_drawn = true;
                 let rgba = PPU::get_rgba(window_pixel);
                 frame_buffer[idx]     = rgba[0];
                 frame_buffer[idx + 1] = rgba[1];
                 frame_buffer[idx + 2] = rgba[2];
             }
-
             if let Some(sprite_pixel) = self.find_sprite_pixel(lcd_x, bus) {
                 let rgba = PPU::get_rgba(sprite_pixel);
                 frame_buffer[idx]     = rgba[0];
@@ -460,22 +501,9 @@ impl PPU {
             }
 
             lcd_x += 1;
-
-            /* for pixel in bg_pixels {
-                let idx = (lcd_x as usize + (lcd_y as usize * LCD_WIDTH as usize)) * 4;
-                let rgba = PPU::get_rgba(pixel);
-                frame_buffer[idx]     = rgba[0];
-                frame_buffer[idx + 1] = rgba[1];
-                frame_buffer[idx + 2] = rgba[2];
-                if let Some(window_pixel) = PPU::get_window_pixel(lcd_x, bus) {
-                    let rgba = PPU::get_rgba(pixel);
-                    frame_buffer[idx]     = rgba[0];
-                    frame_buffer[idx + 1] = rgba[1];
-                    frame_buffer[idx + 2] = rgba[2];
-                }
-
-                lcd_x += 1;
-            } */
+        }
+        if window_drawn {
+            self.window_y_counter += 1;
         }
     }
 
@@ -508,7 +536,7 @@ impl PPU {
         }
     }
 
-    fn get_two_bit_byte_pixels(byte1: u8, byte2: u8) -> [u8; 8] {
+    fn get_byte_pixels(byte1: u8, byte2: u8) -> [u8; 8] {
         [
             ((byte1 >> 7) & 0b01) | ((byte2 >> 6) & 0b10),
             ((byte1 >> 6) & 0b01) | ((byte2 >> 5) & 0b10),
@@ -520,17 +548,4 @@ impl PPU {
             (byte1        & 0b01) | ((byte2 << 1) & 0b10),
         ]
     }
-
-    fn get_byte_pixels(byte1: u8, byte2: u8, palette: u8) -> [Pixel; 8] {
-        [
-            PPU::get_pixel(PPU::get_palette(((byte1 >> 7) & 0b01) | ((byte2 >> 6) & 0b10), palette)),
-            PPU::get_pixel(PPU::get_palette(((byte1 >> 6) & 0b01) | ((byte2 >> 5) & 0b10), palette)),
-            PPU::get_pixel(PPU::get_palette(((byte1 >> 5) & 0b01) | ((byte2 >> 4) & 0b10), palette)),
-            PPU::get_pixel(PPU::get_palette(((byte1 >> 4) & 0b01) | ((byte2 >> 3) & 0b10), palette)),
-            PPU::get_pixel(PPU::get_palette(((byte1 >> 3) & 0b01) | ((byte2 >> 2) & 0b10), palette)),
-            PPU::get_pixel(PPU::get_palette(((byte1 >> 2) & 0b01) | ((byte2 >> 1) & 0b10), palette)),
-            PPU::get_pixel(PPU::get_palette(((byte1 >> 1) & 0b01) | (byte2        & 0b10), palette)),
-            PPU::get_pixel(PPU::get_palette((byte1        & 0b01) | ((byte2 << 1) & 0b10), palette)),
-        ]
-    }
 }

src/render.rs

@@ -65,7 +65,6 @@ pub fn start_eventloop() {
             },
             Event::MainEventsCleared => {
                 emulator.run(Cycles(70224), pixels.get_frame());
-                // emulator.draw(pixels.get_frame());
 
                 thread::sleep(time::Duration::from_millis(1));
                 window.request_redraw();