Building My First Emulator: A CHIP-8 Journey in Rust
When I decided to build a CHIP-8 emulator, I had no idea how much I'd learn along the way. This was my first time creating an emulator and my first big Rust project—quite the combination! But looking back now, with both a desktop and web version running, I couldn't be more proud of what I've accomplished.
Why CHIP-8?
CHIP-8 is the perfect starting point for emulator development. It's simple enough to be approachable but complex enough to teach you real emulation concepts. With only 35 opcodes, 4KB of memory, and a 64x32 monochrome display, it's manageable yet challenging.
Plus, I wanted to really dive into Rust. What better way to learn than building something complex?
The Core: Platform-Agnostic Interpreter
I started by building the core CHIP-8 interpreter—the brain of the emulator. This handles:
- CPU emulation with 16 8-bit registers
- 4KB of RAM
- A 16-level stack
- Two 60Hz timers (delay and sound)
- The full instruction set
Writing this in Rust taught me so much about ownership and borrowing. The compiler kept me honest, catching bugs before they became problems. Every error message was a learning opportunity.
The beauty of separating the core logic? I could reuse it for both desktop and web versions later!
Desktop Version: SDL2 Window to the Past
For the desktop frontend, I used SDL2 to handle graphics, input, and window management. This was my first time working with SDL2, and it was surprisingly straightforward.
The desktop version lets you:
- Load ROM files from your filesystem
- Play games with keyboard input (mapped to CHIP-8's 16-key hexadecimal keypad)
- See the classic 64x32 display scaled up to a comfortable size
Web Version: WebAssembly Magic
This is where things got really exciting. I wanted people to play my emulator without installing anything, so I dove into WebAssembly.
Using wasm-pack, I compiled my Rust code to WebAssembly and created a browser-based version. The same core interpreter, now running in your browser with near-native performance!
The web version taught me:
- How to bridge Rust and JavaScript
- Working with the browser's canvas API
- Handling user input in web contexts
- Deploying WebAssembly applications
Seeing my Rust code run in a browser for the first time was genuinely magical.
Challenges Along the Way
Not everything went smoothly (does it ever?):
The wasm32 Target Mystery: I initially installed Rust via Homebrew, which didn't include the WebAssembly target. Switching to Rustup and adding wasm32-unknown-unknown solved it, but it was a confusing detour.
LSP Configuration Headaches: Getting my Neovim setup to work with both Rust and JavaScript auto-formatting took some trial and error. But now my workflow is smooth!
Opcode Implementation: Some instructions were straightforward, but others (looking at you, display drawing with XOR) required careful testing with multiple ROMs to get right.
What I Learned
This project taught me far more than just Rust syntax:
- Systems Programming: Understanding how CPUs work, memory management, and instruction cycles
- Cross-Platform Development: Building for both native desktop and web from a single codebase
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Project Structure: Organizing code into modules (
chip8_core,desktop,wasm,website) - Debugging: Using test ROMs to verify my implementation
- Modern Web Tech: WebAssembly isn't just hype—it's genuinely powerful
Try It Yourself!
You can play the emulator right now at minipliy.net/chip8 or check out the source code on GitHub.
Final Thoughts
If you're learning Rust or curious about emulator development, I highly recommend starting with CHIP-8. It's challenging enough to push your skills but achievable enough to finish. And seeing those retro games come to life through code you wrote? Absolutely worth it.
Big thanks to aquova's CHIP-8 tutorial for guidance along the way!
Want to build your own emulator? Start with CHIP-8, embrace the compiler errors, and enjoy the journey. You'll learn more than you expect.
Made with Love and Rust
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