From f2a68e629451a2c9240c2ce2f53a750d39baa8af Mon Sep 17 00:00:00 2001 From: Riyyi Date: Mon, 17 Oct 2022 13:27:25 +0200 Subject: [PATCH] Emulator: Add initial pixel FIFO to PPU --- src/ppu.cpp | 110 ++++++++++++++++++++++++++++++++++++++++++++++++++++ src/ppu.h | 29 ++++++++++++++ 2 files changed, 139 insertions(+) diff --git a/src/ppu.cpp b/src/ppu.cpp index 4742968..0908d44 100644 --- a/src/ppu.cpp +++ b/src/ppu.cpp @@ -49,6 +49,10 @@ void PPU::update() // OAM logic goes here.. if (m_clocks_into_frame % 80 == 0) { + // Clear FIFOs + m_pixel_fifo.background = {}; + m_pixel_fifo.oam = {}; + m_state = State::PixelTransfer; } break; @@ -128,6 +132,108 @@ void PPU::render() scene.addComponent(m_entity, glm::vec4 { 1.0f }, texture); } +void PPU::pixelFifo() +{ + LCDC lcd_control = static_cast(Emu::the().readMemory(0xff40)); + + // Tile map + uint32_t tile_map_size = 32 * 32; // 1 KiB + uint32_t bg_tile_map_address = (lcd_control & LCDC::BGTileMapArea) ? 0x9c00 : 0x9800; + // uint32_t window_tile_map_address = (lcd_control & LCDC::WindowTileMapArea) ? 0x9c00 : 0x9800; + + // Tile data + // uint32_t tile_data_size = 4096; // 4KiB / 16B = 256 tiles + uint32_t tile_data_address = (lcd_control & LCDC::BGandWindowTileDataArea) ? 0x8000 : 0x8800; + + // ------------------------------------- + // FIFO Pixel Fetcher + + switch (m_pixel_fifo.state) { + case PixelFifo::State::TileIndex: + if (m_pixel_fifo.step == true) { + m_pixel_fifo.step = false; + m_pixel_fifo.state = PixelFifo::State::TileDataLow; + + // Viewport + // https://gbdev.io/pandocs/Scrolling.html#mid-frame-behavior + m_viewport_x = Emu::the().readMemory(0xff43); // TODO: only read lower 3-bits at beginning of scanline + m_viewport_y = Emu::the().readMemory(0xff42); + + // Read the tile map index + uint16_t offset = (((m_viewport_y + m_lcd_y_coordinate) / TILE_HEIGHT) * 32) + + ((m_viewport_x + m_lcd_x_coordinate) / TILE_WIDTH); + m_pixel_fifo.tile_index = Emu::the().readMemory(bg_tile_map_address + offset) & 0xff; + + // Set the tile line we're currently on + m_pixel_fifo.tile_line = (m_viewport_y + m_lcd_y_coordinate) % TILE_HEIGHT; + } + + m_pixel_fifo.step = true; + break; + case PixelFifo::State::TileDataLow: + if (m_pixel_fifo.step == true) { + m_pixel_fifo.step = false; + m_pixel_fifo.state = PixelFifo::State::TileDataHigh; + + // Read tile data + m_pixel_fifo.pixels_lsb = Emu::the().readMemory(tile_data_address + + (m_pixel_fifo.tile_index * TILE_SIZE) // Each tile is 16 bytes + + m_pixel_fifo.tile_line * 2); // Each tile line is 2 bytes + } + + m_pixel_fifo.step = true; + break; + case PixelFifo::State::TileDataHigh: + if (m_pixel_fifo.step == true) { + m_pixel_fifo.step = false; + m_pixel_fifo.state = PixelFifo::State::Sleep; + + // Read tile data + m_pixel_fifo.pixels_msb = Emu::the().readMemory(tile_data_address + + (m_pixel_fifo.tile_index * TILE_SIZE) + + m_pixel_fifo.tile_line * 2 + + 1); + } + + m_pixel_fifo.step = true; + break; + case PixelFifo::State::Sleep: + if (m_pixel_fifo.background.size() <= 9) { + m_pixel_fifo.state = PixelFifo::State::Push; + } + break; + case PixelFifo::State::Push: { + m_pixel_fifo.state = PixelFifo::State::TileIndex; + + for (uint8_t i = 0; i < 8; ++i) { + uint8_t color_index = (m_pixel_fifo.pixels_lsb >> (7 - i) + | ((m_pixel_fifo.pixels_msb >> (7 - i)) << 1)) + & 0x3; + m_pixel_fifo.background.push({ color_index, Palette::BGP }); + } + break; + } + default: + VERIFY_NOT_REACHED(); + }; + + // ------------------------------------- + // Mode 3 Operation + + // The pixel FIFO needs to contain more than 8 pixels to shift one out + if (m_pixel_fifo.background.size() > 8) { + auto pixel = m_pixel_fifo.background.front(); + m_pixel_fifo.background.pop(); + + uint32_t index = (m_lcd_y_coordinate * SCREEN_WIDTH + m_lcd_x_coordinate) * FORMAT_SIZE; + auto color = getPixelColor(pixel.first, pixel.second); + m_screen[index + 0] = color[0]; + m_screen[index + 1] = color[1]; + m_screen[index + 2] = color[2]; + m_lcd_x_coordinate++; + } +} + void PPU::drawTile(uint32_t x, uint32_t y, uint32_t tile_address) { uint32_t viewport_x = Emu::the().readMemory(0xff43); @@ -200,4 +306,8 @@ void PPU::resetFrame() m_clocks_into_frame = 0; m_lcd_x_coordinate = 0; m_lcd_y_coordinate = 0; + + // Clear FIFOs + m_pixel_fifo.background = {}; + m_pixel_fifo.oam = {}; } diff --git a/src/ppu.h b/src/ppu.h index 645e7d8..91600aa 100644 --- a/src/ppu.h +++ b/src/ppu.h @@ -9,6 +9,8 @@ #include #include // uint8_t, uint16_t, uint32_t +#include +#include // std::pair #include "ruc/meta/core.h" @@ -51,9 +53,32 @@ public: OBP1 = 0xff49, // OBJ palette 1 }; + struct PixelFifo { + enum State : uint8_t { + TileIndex, + TileDataLow, + TileDataHigh, + Sleep, + Push, + }; + + State state = State::TileIndex; + bool step = false; + uint8_t tile_index = 0; + uint8_t tile_line = 0; + uint8_t pixels_lsb = 0; + uint8_t pixels_msb = 0; + + using Fifo = std::queue>; // colorID, source + + Fifo background; + Fifo oam; + }; + void update() override; void render(); + void pixelFifo(); void drawTile(uint32_t screen_x, uint32_t screen_y, uint32_t tile_address); std::array getPixelColor(uint8_t color_index, Palette palette); @@ -65,6 +90,10 @@ private: uint32_t m_lcd_x_coordinate { 0 }; uint32_t m_lcd_y_coordinate { 0 }; // Note: includes V-Blank + uint8_t m_viewport_x { 0 }; + uint8_t m_viewport_y { 0 }; + PixelFifo m_pixel_fifo; + uint32_t m_entity; std::array m_screen; };