Refactor PPU interrupt requests and fix Scroll X

src/bus.rs

@@ -59,7 +59,7 @@ 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/m3_scy_change.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()) {
         // let game_rom = match ROM::load_file("roms/cpu_instrs_individual/02-interrupts.gb".to_string()) {
@@ -78,7 +78,7 @@ impl Bus {
         };
         let mut data = [0x00; 0x10000];
         // Hardware registers after the bootrom
-        data[0xFF00] = 0b11001111;
+        data[0xFF00] = 0xCF;
         data[0xFF01] = 0x00;
         data[0xFF02] = 0x7E;
         data[0xFF04] = 0x18;
@@ -139,9 +139,14 @@ impl Bus {
         } else if address == LCD_CONTROL_ADDRESS && get_bit(data, BitIndex::I7) {
             self.data[address as usize] = data;
             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 {
+            let byte = self.data[address as usize];
+            self.data[address as usize] = (data & 0b11111000) | (byte & 0b00000111);
         } else if address == JOYPAD_ADDRESS {
-            let byte = self.data[JOYPAD_ADDRESS as usize];
-            self.data[JOYPAD_ADDRESS as usize] = (data & 0b11110000) | (byte & 0b00001111);
+            let byte = self.data[address as usize];
+            self.data[address as usize] = (data & 0b11110000) | (byte & 0b00001111);
         } else {
             self.data[address as usize] = data;
         }

src/emulator.rs

@@ -96,19 +96,11 @@ impl Emulator {
             self.joypad.release(Button::Select);
         }
         if change {
-            self.joypad.update(&mut self.bus);
             self.bus.set_interrupt_flag(Interrupt::Joypad, true);
         }
     }
 
-    pub fn draw(&mut self, frame: &mut [u8]) {
-        let ppu_frame = self.ppu.get_rgba_frame();
-        for (i, pixel) in frame.chunks_exact_mut(4).enumerate() {
-            pixel.copy_from_slice(&ppu_frame[i]);
-        }
-    }
-
-    pub fn run(&mut self, cpu_cycles: Cycles) {
+    pub fn run(&mut self, cpu_cycles: Cycles, frame_buffer: &mut [u8]) {
         self.cpu.reset_cycles();
         while self.cpu.get_cycles().0 <= cpu_cycles.0 {
             self.cpu.run(&mut self.bus);
@@ -116,7 +108,7 @@ impl Emulator {
                 self.bus.reset_timer = false;
                 self.timer.reset(&mut self.bus);
             }
-            self.ppu.do_cycles(&mut self.bus, self.cpu.get_last_op_cycles());
+            self.ppu.do_cycles(&mut self.bus, self.cpu.get_last_op_cycles(), frame_buffer);
             self.timer.do_cycles(&mut self.bus, self.cpu.get_last_op_cycles());
 
             // 1 CPU cycle = 238.42ns
@@ -127,13 +119,14 @@ impl Emulator {
 
     pub fn cpu_loop(&mut self) {
         let mut exit = false;
+        let mut frame: [u8; 144 * 160] = [0; 144 * 160];
         while !exit {
             self.cpu.run(&mut self.bus);
             if self.bus.reset_timer {
                 self.bus.reset_timer = false;
                 self.timer.reset(&mut self.bus);
             }
-            self.ppu.do_cycles(&mut self.bus, self.cpu.get_last_op_cycles());
+            self.ppu.do_cycles(&mut self.bus, self.cpu.get_last_op_cycles(), &mut frame);
             self.timer.do_cycles(&mut self.bus, self.cpu.get_last_op_cycles());
 
             // exit = self.cpu.get_exec_calls_count() >= 1258895; // log 1

src/joypad.rs

@@ -68,7 +68,7 @@ impl Joypad {
         };
     }
 
-    pub fn update(&self, bus: &mut Bus) {
+    pub fn read(&self, bus: &mut Bus) -> u8 {
         let byte = bus.read(JOYPAD_ADDRESS);
         let direction = !get_bit(byte, BitIndex::I4);
         let action = !get_bit(byte, BitIndex::I5);
@@ -83,7 +83,6 @@ impl Joypad {
         ) | (
             (!((direction && self.right) || (action && self.a)) as u8)
         );
-        println!("New joypad write: {:08b}", data);
-        bus.force_write(JOYPAD_ADDRESS, data);
+        return data;
     }
 }

src/ppu.rs

@@ -91,6 +91,7 @@ pub enum LCDStatus {
 }
 
 pub struct PPU {
+    prev_state: bool,
     cycles: Cycles,
     rgba_frame: [[u8; 4]; FRAME_BUFFER_LENGTH as usize],
 }
@@ -103,6 +104,7 @@ enum TileNumber {
 impl PPU {
     pub fn new() -> Self {
         Self {
+            prev_state: false,
             cycles: Cycles(0),
             rgba_frame: [[0xFF, 0xFF, 0xFF, 0]; FRAME_BUFFER_LENGTH as usize],
         }
@@ -116,15 +118,15 @@ impl PPU {
         self.cycles.0 += cycles.0;
     }
 
-    pub fn do_cycles(&mut self, bus: &mut Bus, cycles: Cycles) {
+    pub fn do_cycles(&mut self, bus: &mut Bus, cycles: Cycles, frame_buffer: &mut [u8]) {
         let mut count = 0;
         while count < cycles.0 {
-            self.cycle(bus);
+            self.cycle(bus, frame_buffer);
             count += 1;
         }
     }
 
-    pub fn cycle(&mut self, bus: &mut Bus) {
+    pub fn cycle(&mut self, bus: &mut Bus, frame_buffer: &mut [u8]) {
         if !PPU::get_lcd_control(bus, LCDControl::LCDEnable) {
             self.increment_cycles(Cycles(1));
             return;
@@ -134,26 +136,21 @@ impl PPU {
             if self.cycles.0 == 0 {
                 // Mode 2 OAM scan
                 PPU::set_lcd_status(bus, LCDStatus::ModeFlag(LCDStatusModeFlag::SearchingOAM), true);
-                if PPU::get_lcd_status(bus, LCDStatus::Mode2OAMInterrupt) {
-                    PPU::request_interrupt(bus, Interrupt::LCDSTAT);
-                }
+                self.stat_interrupt(bus);
             } else if self.cycles.0 == 80 + 1 {
                 // Mode 3 drawing pixel line. This could also last 289 cycles
-                self.draw_line(bus);
+                self.draw_line(bus, frame_buffer);
                 PPU::set_lcd_status(bus, LCDStatus::ModeFlag(LCDStatusModeFlag::TransferringToLCD), true);
             } else if self.cycles.0 == 80 + 172 + 1 {
                 // 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);
-                if PPU::get_lcd_status(bus, LCDStatus::Mode0HBlankInterrupt) {
-                    PPU::request_interrupt(bus, Interrupt::LCDSTAT);
-                }
+                self.stat_interrupt(bus);
             }
         } else if PPU::get_lcd_y(bus) == 144 && self.cycles.0 == 0 {
             // Mode 1 Vertical blank
+            bus.set_interrupt_flag(Interrupt::VBlank, true);
             PPU::set_lcd_status(bus, LCDStatus::ModeFlag(LCDStatusModeFlag::VBlank), true);
-            if PPU::get_lcd_status(bus, LCDStatus::Mode1VBlankInterrupt) {
-                PPU::request_interrupt(bus, Interrupt::VBlank);
-            }
+            self.stat_interrupt(bus);
         }
 
         self.increment_cycles(Cycles(1));
@@ -167,21 +164,28 @@ impl PPU {
             if PPU::get_lcd_y(bus) > 153 {
                 PPU::set_lcd_y(bus, 0);
             }
-            PPU::check_lyc(bus);
+            self.check_lyc(bus);
         }
     }
 
-    fn check_lyc(bus: &mut 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);
+        }
+    }
+
+    fn check_lyc(&mut self, bus: &mut Bus) {
         let lyc_compare = PPU::get_lcd_y(bus) == bus.read(LCD_Y_COMPARE_ADDRESS);
-        if PPU::get_lcd_status(bus, LCDStatus::LYCInterrupt) && lyc_compare {
-            PPU::set_lcd_status(bus, LCDStatus::LYCFlag, lyc_compare);
-            PPU::request_interrupt(bus, Interrupt::LCDSTAT);
-        }
-    }
-
-    fn request_interrupt(bus: &mut Bus, interrupt: Interrupt) {
-        if PPU::get_lcd_control(bus, LCDControl::LCDEnable) {
-            bus.set_interrupt_flag(interrupt, true);
+        PPU::set_lcd_status(bus, LCDStatus::LYCFlag, lyc_compare);
+        if lyc_compare && PPU::get_lcd_status(bus, LCDStatus::LYCInterrupt) {
+            bus.set_interrupt_flag(Interrupt::LCDSTAT, true);
+            self.prev_state = true;
         }
     }
 
@@ -190,7 +194,7 @@ impl PPU {
     }
 
     fn set_lcd_y(bus: &mut Bus, val: u8) {
-        bus.write(LCD_Y_ADDRESS, val);
+        bus.force_write(LCD_Y_ADDRESS, val);
     }
 
     fn get_scroll_x(bus: &Bus) -> u8 {
@@ -216,7 +220,7 @@ impl PPU {
 
     fn set_lcd_control(bus: &mut Bus, control: LCDControl, val: bool) {
         let mut byte = bus.read(LCD_CONTROL_ADDRESS);
-        bus.write(LCD_CONTROL_ADDRESS, control.set(byte, val));
+        bus.force_write(LCD_CONTROL_ADDRESS, control.set(byte, val));
     }
 
     pub fn get_lcd_status(bus: &Bus, status: LCDStatus) -> bool {
@@ -251,7 +255,7 @@ impl PPU {
                 LCDStatusModeFlag::TransferringToLCD => (byte & 0b11111100) | 3,
             },
         };
-        bus.write(LCD_STATUS_ADDRESS, byte);
+        bus.force_write(LCD_STATUS_ADDRESS, byte);
     }
 
     fn get_tile_bytes(x: u8, y: u8, tile_number_type: TileNumber, default_method: bool, bus: &Bus) -> (u8, u8) {
@@ -277,15 +281,15 @@ impl PPU {
 
     fn get_window_pixel(lcd_x: u8, bus: &Bus) -> Option<Pixel> {
         let lcd_y = PPU::get_lcd_y(bus);
-        let window_x = (PPU::get_window_x(bus) as i8 - 7) as u8;
+        let window_x = PPU::get_window_x(bus);
         let window_y = PPU::get_window_y(bus);
 
-        if !PPU::get_lcd_control(bus, LCDControl::WindowEnable) || window_x != lcd_x || window_y != lcd_y {
+        if !PPU::get_lcd_control(bus, LCDControl::WindowEnable) || lcd_x < (window_x.saturating_sub(7)) || window_y != lcd_y {
             return None;
         }
 
-        let x = lcd_x - window_x;
-        let y = lcd_y - window_x;
+        let x = lcd_x.wrapping_sub(window_x.saturating_sub(7));
+        let y = lcd_y.wrapping_sub(window_y);
 
         let default_mode = PPU::get_lcd_control(bus, LCDControl::TileAddressMode);
         let tilemap_area = match PPU::get_lcd_control(bus, LCDControl::WindowTileMapAddress) {
@@ -300,7 +304,7 @@ impl PPU {
         Some(pixels[(x as usize).rem_euclid(8)])
     }
 
-    fn draw_line(&mut self, bus: &Bus) {
+    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 {
@@ -320,15 +324,36 @@ impl PPU {
 
             let bg_pixels = PPU::get_byte_pixels(tile_byte_1, tile_byte_2, palette);
 
-            for pixel in bg_pixels {
-                let idx = lcd_x as usize + (lcd_y as usize * LCD_WIDTH as usize);
-                self.rgba_frame[idx] = PPU::get_rgba(pixel);
+            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) {
+                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;
+
+            /* 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) {
-                    self.rgba_frame[idx] = PPU::get_rgba(window_pixel);
+                    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;
-            }
+            } */
         }
     }
 
@@ -373,8 +398,4 @@ impl PPU {
             PPU::get_pixel(PPU::get_palette((byte1        & 0b01) | ((byte2 << 1) & 0b10), palette)),
         ]
     }
-
-    pub fn get_rgba_frame(&self) -> &[[u8; 4]; FRAME_BUFFER_LENGTH as usize] {
-        &self.rgba_frame
-    }
 }

src/render.rs

@@ -64,10 +64,10 @@ pub fn start_eventloop() {
                 *control_flow = ControlFlow::Exit
             },
             Event::MainEventsCleared => {
-                emulator.run(Cycles(70224));
-                emulator.draw(pixels.get_frame());
+                emulator.run(Cycles(70224), pixels.get_frame());
+                // emulator.draw(pixels.get_frame());
 
-                // thread::sleep(time::Duration::from_millis(14));
+                // thread::sleep(time::Duration::from_millis(1000));
                 window.request_redraw();
             },
             Event::RedrawRequested(_) => {