New Project: Game Boy Emulator

Game Boy Emulator running a "test rom" which tests instructions to see which work

Over the past week I started one last big project in my spree to test out what I can do these past few months. As seen in the above screenshot, I've been working on a Game Boy emulator! As with my past projects, the only dependency is SFML which I use for rendering (I'm thinking about splitting up the project into two to remove the SFML dependency, since the SFML code is literally a few dozen lines).

The project has been pretty smooth so far and I'm able to run very basic ROMs but am still a ways off from running full fledged games. Probably the most difficult part of setting up the emulator is that you need quite a lot already established to run even the most basic ROMs, and on top of that I had to manually implement over 400 instructions for the modified Z80 processor being emulated, which took 3 days of grunt coding to finish. Thankfully, I was able to use Imran Nazar's jsGB emulator as a base off which I implemented the instructions. Unfortunately, while a good reference, I had to use another reference to go over every instruction and correct mistakes I found, which were quite a few and a bit frustrating (and I'm still not sure I caught all the mistakes).

At least for me, it's almost guaranteed that writing hundreds of instructions will result in some typos and mistakes, which is where test roms come into play. Thankfully, there exists an entire suite of test ROMs that test all the instructions and features of the Game Boy to see if it is compliant. I've been using the BGB emulator's debugger as a base to compare my emulator to. I go through each instruction and make sure they, and the registers, match BGB's.

On GitHub there is a private repository for this project setup, and hopefully in the next few weeks I can make it public. This project really takes me back because the Game Boy is my all time favorite console, and it's really fun to be able to implement my own take on it.