Chip-8 Emulator

A fully-functional Chip-8 emulator built from scratch in C++ with SDL2 graphics and audio support.

Features

• All 35 Chip-8 opcodes implemented
• 64x32 pixel display with SDL2 rendering
• Keyboard input support
• Sound effects (beep tone)
• 60 FPS rendering

Architecture

Chip-8 is a virtual machine from the 1970s designed to make programming video games easier on early microcomputers.

System Specifications

• Memory: 4 KB (4096 bytes)
  • 0x000-0x1FF: Reserved for interpreter and fonts
  • 0x200-0xFFF: Program/ROM space
• Registers:
  • 16 8-bit general-purpose registers (V0-VF)
  • VF doubles as a flag register for arithmetic operations
  • 16-bit index register (I)
  • 16-bit program counter (PC)
  • 8-bit stack pointer (SP)
• Display: 64×32 pixels, monochrome
• Timers:
  • Delay timer (counts down at 60 Hz)
  • Sound timer (beeps when > 0, counts down at 60 Hz)
• Stack: 16 levels for subroutine calls
• Keypad: 16-key hexadecimal input

Dependencies

• SDL2 library

Installation

Arch Linux:

sudo pacman -S sdl2

Ubuntu/Debian:

sudo apt-get install libsdl2-dev

macOS:

brew install sdl2

Building

1. Clone the repo

git clone https://github.com/eko-071/chip8-emulator.git

2. Make it

make

Usage

./chip8 <path-to-rom-file>

Example:

./chip8 roms/PONG.ch8

Keyboard Mapping

The original Chip-8 keypad is mapped to keyboard keys:

Chip-8 Keypad:          QWERTY Keyboard:
┌─┬─┬─┬─┐               ┌─┬─┬─┬─┐
│1│2│3│C│               │1│2│3│4│
├─┼─┼─┼─┤               ├─┼─┼─┼─┤
│4│5│6│D│               │Q│W│E│R│
├─┼─┼─┼─┤      =        ├─┼─┼─┼─┤
│7│8│9│E│               │A│S│D│F│
├─┼─┼─┼─┤               ├─┼─┼─┼─┤
│A│0│B│F│               │Z│X│C│V│
└─┴─┴─┴─┘               └─┴─┴─┴─┘

Controls:

• ESC - Quit emulator
• Keyboard keys as mapped above

Game-Specific Controls

PONG:

• Left paddle: 1 (up), Q (down)
• Right paddle: 4 (up), R (down)

TETRIS:

• Q - Rotate
• W - Drop
• E - Move right
• A - Move left

Project Structure

.
├── LICENSE
├── Makefile
├── README.md
├── roms # Some ROM files (.ch8)
│   ├── Blinky.ch8
│   ├── Pong.ch8
│   └── Tetris.ch8
└── src
    ├── chip8.cpp # Core emulator logic and opcodes implementation
    ├── chip8.h # Chip-8 class declaration
    └── main.cpp # SDL2 setup, rendering, input handling and stuff

Implementation Details

Instruction Set

The emulator implements all 35 Chip-8 instructions, including:

• Arithmetic: ADD, SUB, AND, OR, XOR, shift operations
• Graphics: Draw sprites with XOR mode, collision detection
• Flow control: Jump, call/return subroutines, conditional skips
• Memory: Load/store registers, BCD conversion
• Timers: Delay and sound timer operations
• Input: Key press detection (blocking and non-blocking)

Display

Graphics are rendered using SDL2:

• Each Chip-8 pixel is scaled 10× for visibility (640×320 window)
• XOR-based sprite drawing for collision detection
• 60 FPS rendering

Audio

Simple square wave generation at 440 Hz (musical note A) plays when sound_timer > 0.

Resources

• Cowgod's Chip-8 Technical Reference
• Chip-8 ROMs Archive