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Emulator: Separate pixel FIFO states into different functions

master
Riyyi 2 years ago
parent
91884d65fb
commit
301c9343da
2 changed files with 169 additions and 132 deletions
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  1. 267
      src/ppu.cpp
  2. 34
      src/ppu.h

267
src/ppu.cpp
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@ -5,7 +5,7 @@
* SPDX-License-Identifier: MIT
*/
#include <cstdint> // uint32_t
#include <cstdint> // uint8_t, uint16_t, uint32_t
#include <memory> // 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<Inferno::SpriteComponent>(m_entity, glm::vec4 { 1.0f }, texture);
}
void PPU::pixelFifo()
void PPU::resetFrame()
{
LCDC lcd_control = static_cast<LCDC>(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<uint8_t, 3> PPU::getPixelColor(uint8_t color_index, Palette palette)
{
@ -266,10 +174,129 @@ std::array<uint8_t, 3> 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<LCDC>(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++;
}
}

34
src/ppu.h
Unescape View File

@ -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<std::pair<uint8_t, Palette>>; // 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<uint8_t, 3> 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 };

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