From 301c9343dabb5c487185ca9ef032c2e2935c56d9 Mon Sep 17 00:00:00 2001 From: Riyyi Date: Tue, 18 Oct 2022 21:24:06 +0200 Subject: [PATCH] Emulator: Separate pixel FIFO states into different functions --- src/ppu.cpp | 267 +++++++++++++++++++++++++++++----------------------- src/ppu.h | 34 ++++--- 2 files changed, 169 insertions(+), 132 deletions(-) diff --git a/src/ppu.cpp b/src/ppu.cpp index a66d828..a74dcea 100644 --- a/src/ppu.cpp +++ b/src/ppu.cpp @@ -5,7 +5,7 @@ * SPDX-License-Identifier: MIT */ -#include // uint32_t +#include // uint8_t, uint16_t, uint32_t #include // std::make_shared #include "glm/ext/vector_float3.hpp" // glm::vec3 @@ -56,7 +56,7 @@ void PPU::update() } break; case State::PixelTransfer: - pixelFifo(); + updatePixelFifo(); if (m_lcd_x_coordinate == 160) { m_lcd_x_coordinate = 0; @@ -112,129 +112,37 @@ void PPU::render() scene.addComponent(m_entity, glm::vec4 { 1.0f }, texture); } -void PPU::pixelFifo() +void PPU::resetFrame() { - LCDC lcd_control = static_cast(Emu::the().readMemory(0xff40)); - - // Tile map - uint32_t bg_tile_map_address = (lcd_control & LCDC::BGTileMapArea) ? 0x9c00 : 0x9800; - // uint32_t window_tile_map_address = (lcd_control & LCDC::WindowTileMapArea) ? 0x9c00 : 0x9800; + m_state = State::OAMSearch; + m_clocks_into_frame = 0; + m_lcd_x_coordinate = 0; + m_lcd_y_coordinate = 0; +} - // Tile data - uint32_t tile_data_address = (lcd_control & LCDC::BGandWindowTileDataArea) ? 0x8000 : 0x8800; +// ----------------------------------------- +uint32_t PPU::getBgTileDataAddress(uint8_t tile_index) +{ // https://gbdev.io/pandocs/Tile_Data.html - auto getBgTileDataAddress = [&](uint8_t tile_index) -> uint32_t { - switch (tile_data_address) { - case 0x8000: - // 0x8000-0x8fff: index 0 => 255 - return tile_data_address + (tile_index * TILE_SIZE); // Each tile is 16 bytes - case 0x8800: - // 0x8800-0x8fff: index 128 => 255 (or -128 => -1) - // 0x9000-0x97ff: index 0 => 127 - if (tile_index <= 127) { - return tile_data_address + 0x800 + (tile_index * TILE_SIZE); // Each tile is 16 bytes - } - else { - return tile_data_address + ((tile_index - 128) * TILE_SIZE); // Each tile is 16 bytes - } - default: - VERIFY_NOT_REACHED(); - return 0; - }; - }; - - // ------------------------------------- - // FIFO Pixel Fetcher - - switch (m_pixel_fifo.state) { - case PixelFifo::State::TileIndex: - if (!m_pixel_fifo.step) { - m_pixel_fifo.step = true; - } - else { - 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_pixel_fifo.x_coordinate) / TILE_WIDTH); - m_pixel_fifo.x_coordinate += 8; - 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; - } - break; - case PixelFifo::State::TileDataLow: - if (!m_pixel_fifo.step) { - m_pixel_fifo.step = true; - } - else { - m_pixel_fifo.step = false; - m_pixel_fifo.state = PixelFifo::State::TileDataHigh; - - // Read tile data - m_pixel_fifo.pixels_lsb = Emu::the().readMemory( - getBgTileDataAddress(m_pixel_fifo.tile_index) - + m_pixel_fifo.tile_line * 2); // Each tile line is 2 bytes - } - break; - case PixelFifo::State::TileDataHigh: - if (!m_pixel_fifo.step) { - m_pixel_fifo.step = true; + switch (m_pixel_fifo.tile_data_address) { + case 0x8000: + // 0x8000-0x8fff: index 0 => 255 + return m_pixel_fifo.tile_data_address + (tile_index * TILE_SIZE); // Each tile is 16 bytes + case 0x8800: + // 0x8800-0x8fff: index 128 => 255 (or -128 => -1) + // 0x9000-0x97ff: index 0 => 127 + if (tile_index <= 127) { + return m_pixel_fifo.tile_data_address + 0x800 + (tile_index * TILE_SIZE); // Each tile is 16 bytes } else { - m_pixel_fifo.step = false; - m_pixel_fifo.state = PixelFifo::State::Sleep; - - // Read tile data - m_pixel_fifo.pixels_msb = Emu::the().readMemory( - getBgTileDataAddress(m_pixel_fifo.tile_index) - + m_pixel_fifo.tile_line * 2 // Each tile line is 2 bytes - + 1); - } - 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 }); + return m_pixel_fifo.tile_data_address + ((tile_index - 128) * TILE_SIZE); // Each tile is 16 bytes } - break; default: VERIFY_NOT_REACHED(); + return 0; }; - - // ------------------------------------- - // 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++; - } -} +}; std::array PPU::getPixelColor(uint8_t color_index, Palette palette) { @@ -266,10 +174,129 @@ std::array PPU::getPixelColor(uint8_t color_index, Palette palette) return {}; } -void PPU::resetFrame() +void PPU::updatePixelFifo() { - m_state = State::OAMSearch; - m_clocks_into_frame = 0; - m_lcd_x_coordinate = 0; - m_lcd_y_coordinate = 0; + switch (m_pixel_fifo.state) { + case PixelFifo::State::TileIndex: + tileIndex(); + break; + case PixelFifo::State::TileDataLow: + tileDataLow(); + break; + case PixelFifo::State::TileDataHigh: + tileDataHigh(); + break; + case PixelFifo::State::Sleep: + sleep(); + break; + case PixelFifo::State::Push: + pushFifo(); + break; + default: + VERIFY_NOT_REACHED(); + }; + + pushPixel(); +} + +void PPU::tileIndex() +{ + if (!m_pixel_fifo.step) { + m_pixel_fifo.step = true; + } + else { + m_pixel_fifo.step = false; + m_pixel_fifo.state = PixelFifo::State::TileDataLow; + + LCDC lcd_control = static_cast(Emu::the().readMemory(0xff40)); + + // Tile map + 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 + m_pixel_fifo.tile_data_address = (lcd_control & LCDC::BGandWindowTileDataArea) ? 0x8000 : 0x8800; + + // Viewport + // https://gbdev.io/pandocs/Scrolling.html#mid-frame-behavior + m_pixel_fifo.viewport_x = Emu::the().readMemory(0xff43); // TODO: only read lower 3-bits at beginning of scanline + m_pixel_fifo.viewport_y = Emu::the().readMemory(0xff42); + + // Read the tile map index + uint16_t offset = (((m_pixel_fifo.viewport_y + m_lcd_y_coordinate) / TILE_HEIGHT) * 32) + + ((m_pixel_fifo.viewport_x + m_pixel_fifo.x_coordinate) / TILE_WIDTH); + m_pixel_fifo.x_coordinate += 8; + m_pixel_fifo.tile_index = Emu::the().readMemory(bg_tile_map_address + offset); + + // Set the tile line we're currently on + m_pixel_fifo.tile_line = (m_pixel_fifo.viewport_y + m_lcd_y_coordinate) % TILE_HEIGHT; + } +} + +void PPU::tileDataLow() +{ + if (!m_pixel_fifo.step) { + m_pixel_fifo.step = true; + } + else { + m_pixel_fifo.step = false; + m_pixel_fifo.state = PixelFifo::State::TileDataHigh; + + // Read tile data + m_pixel_fifo.pixels_lsb = Emu::the().readMemory( + getBgTileDataAddress(m_pixel_fifo.tile_index) + + m_pixel_fifo.tile_line * 2); // Each tile line is 2 bytes + } +} + +void PPU::tileDataHigh() +{ + if (!m_pixel_fifo.step) { + m_pixel_fifo.step = true; + } + else { + m_pixel_fifo.step = false; + m_pixel_fifo.state = PixelFifo::State::Sleep; + + // Read tile data + m_pixel_fifo.pixels_msb = Emu::the().readMemory( + getBgTileDataAddress(m_pixel_fifo.tile_index) + + m_pixel_fifo.tile_line * 2 // Each tile line is 2 bytes + + 1); + } +} + +void PPU::sleep() +{ + if (m_pixel_fifo.background.size() <= TILE_WIDTH + 1) { + m_pixel_fifo.state = PixelFifo::State::Push; + } +} + +void PPU::pushFifo() +{ + m_pixel_fifo.state = PixelFifo::State::TileIndex; + + for (uint8_t i = 0; i < TILE_WIDTH; ++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 }); + } +} + +void PPU::pushPixel() +{ + // 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++; + } } diff --git a/src/ppu.h b/src/ppu.h index 4abbc2e..65ecf86 100644 --- a/src/ppu.h +++ b/src/ppu.h @@ -62,13 +62,16 @@ public: Push, }; - State state = State::TileIndex; - bool step = false; - uint8_t x_coordinate = 0; - uint8_t tile_index = 0; - uint8_t tile_line = 0; - uint8_t pixels_lsb = 0; - uint8_t pixels_msb = 0; + State state { State::TileIndex }; + bool step { false }; + uint32_t tile_data_address { 0 }; + uint8_t viewport_x { 0 }; + uint8_t viewport_y { 0 }; + uint8_t x_coordinate { 0 }; + 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 @@ -78,20 +81,27 @@ public: void update() override; void render(); + void resetFrame(); - void pixelFifo(); +private: + uint32_t getBgTileDataAddress(uint8_t tile_index); std::array getPixelColor(uint8_t color_index, Palette palette); - void resetFrame(); + void updatePixelFifo(); + void tileIndex(); + void tileDataLow(); + void tileDataHigh(); + void sleep(); + void pushFifo(); + void pushPixel(); + + // ------------------------------------- -private: State m_state { State::OAMSearch }; uint32_t m_clocks_into_frame { 0 }; 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 { 0 };