Elaris

A NES (Nintendo Entertainment System) emulator written in Rust. Work in progress.

Features

• 6502 CPU – Full instruction set including undocumented opcodes; nestest-compatible
• PPU – Background and sprite rendering, nametable mirroring, OAM, PPUMASK ($2001) show bg/sprite, left 8-pixel clipping, grayscale, color emphasis, 256×240 framebuffer
• APU – Pulse (×2), triangle, noise, and DMC channels; frame counter (4-step and 5-step); 44.1 kHz audio
• Cartridge – iNES (.nes) loading; mappers: NROM (0), MMC1 (1)
• Controller – Port 1 ($4016) shift-register protocol
• Display – 256×240 window via minifb; scaled to fit
• Audio – Output via rodio (default device)

Requirements

• Rust (e.g. rustup default stable)

Build & Run

cargo build --release
cargo run --release -- path/to/game.nes

Without a path, the emulator defaults to test/nestest.nes (for CPU verification).

Usage

elaris [path/to/rom.nes]

• Escape – Close the window and exit.

Controller (port 1): Keyboard mapping — A = Z, B = X, Select = Shift, Start = Enter, D-pad = Arrow keys. Button state is latched when the game writes to $4016.

Nestest

To verify the CPU against nestest:

cargo run --release -- test/nestest.nes

The emulator starts at the nestest entry point ($C000) and runs until it hits a JAM. Compare cycle count and final state with nestest.log if needed.

Project layout

Path	Description
src/main.rs	Entry point, window, audio sink, frame loop
src/lib.rs	Crate root and module list
src/bus.rs	Memory map, PPU/APU/controller/cartridge dispatch
src/cpu/	6502 CPU and status flags
src/ppu/	PPU timing, background, sprites, OAM, framebuffer
src/apu/	APU channels, frame counter, mixer, sample buffer
src/cartridge/	iNES loading and mappers (NROM, MMC1)
src/controller.rs	NES controller shift register

License

GPL-3.0-or-later. See LICENSE.md.