brightNES

Cycle-accurate NES emulator

Important

BrightNES started out as a fun way to learn emulator development and some fundamentals, and it's reached a point where I've learnt what I have to learn. The time investment required in getting feature parity with existing emulators such as Mesen and Nintendulator doesn't make sense, and I would not be developing this further.

Features

• Instruction Stepped, Cycle Ticked CPU
• Cycle Ticked PPU
• Load external palettes with the -p option
• Smooth horizontal scrolling
• Sprite 0 flag set

Quick Start

brightNES requires CMake and a C compiler to build

Compile with system SDL2

Use this option if you have SDL2 already installed

git clone https://github.com/neov5/brightNES.git && cd brightNES
mkdir build build/release
cmake -B build/release -DSYSTEM_SDL=1 -DCMAKE_BUILD_TYPE=release
cmake --build build/release
./build/release/brightnes <rom_path> [-p|--palette palette_path]

Compile with packaged SDL2

This install builds SDL2 from source along with the emulator

git clone --recurse-submodules https://github.com/neov5/brightNES.git && cd brightNES
mkdir build build/release
cmake -B build/release -DCMAKE_BUILD_TYPE=release
cmake --build build/release
./build/release/brightnes <rom_path> [-p|--palette palette_path]

Debug builds

mkdir build build/debug
cmake -B build/debug [-DSYSTEM_SDL=0/1] -DCMAKE_BUILD_TYPE=debug && cmake --build build/debug
./build/debug/brightnes <rom_path> [-p|--palette palette_path]

Note that the debugger stalls at start, and the window can be a bit unresponsive as a result of not processing SDL events.

Debug Mode

BrightNES supports rudimentary command-line based debugging when compiled with NES_DEBUG defined (set in debug builds). Debug mode breaks on entry and gives you a prompt to step through the program

(cpu:       7) (ppu:      25) DEBUG [PPU r:000 c:025 ctrl:00 mask:00 status:00 v:0000 t:0000 x:0 w:0]
(cpu:       7) (ppu:      25) DEBUG [CPU A:00 X:00 Y:00 PC:8000 S:fd P:34]
>

You can either:

• Step to the first cpu cycle >= X, using s X
• Exit debug mode using e
• Step to the next instruction and printing the CPU/PPU status by hitting enter

In addition, the logs are written to brightnes.log in build/debug.

TODO

• Debug remaining mapper 0 games
  • Ice Climber
  • Ice Hockey
  • SMB rendering when mario is at the top of the screen
• CI/CD setup with GitHub actions
• APU
• Mappers
  • MMC1
  • MMC3
  • MMC5
• Full-featured debug mode?