Version 2 Notice
Version 2 is starting to rollout and updates will be slow. It's initial rollout consists only of a new graphic feature, tilemap printing, which makes the image above much easier to achieve.
Apart from cosmetics, version 2 will tackle a bigger problem as it develops which is wasted CPU cycles and code bloating from version 1. Until verson 2 is complete enjoy it's new graphic feature, tilemap printing, and future updates as they happen.
Additionally it now auto-converts standard png images to tiledata directly and back making development far easier, universal, and more fun.
Gameboy Boilerplate Project
There are a million ways to program for the Gameboy, here I provide a boilerplate assembly project that I like which is commented and documented throughout to get you off the ground. I also include a revised tileset I made which includes many ascii and extended ascii characters.
There have been lots of starter stuff I've seen but many were poorly documented, often very incomplete and very basic to the point where it's not even useable in a real game and would all have to be scrapped. I always wanted to see one that had more to it especially in terms of realism in a real project so I began making my own while having a lot of fun and enjoying game dev-ing on the Gameboy.
My goal is to really make this advanced or at least comprehensive and cover a good range of stuff well so you can just jump right in. Of course as a starter project your more than welcome to dive in and make whatever changes you want, it's your project after all - I just provide the boiler plate stuff.
Contributions Welcome and Encouraged
I'm not the best developer in the world, not by a longshot lol, so I welcome any contributions and hope this can really be expanded by others into a more unified and larger project with a lot of collaboration and ideas from others especially ^_^. If your interested or have something quick you want to add feel free to contribute. Just fork, make changes, and send a pull request.
What is this for?
This is for the original gameboy or DMG Gameboy however it can always be molded pretty easily to the later models and such.
What cartridge does it run on?
Version 2 uses an MBC5 cartridge that has
- 512 ROM Banks (8MB)
- 16 RAM Banks (128KB)
I chose MBC5 for a few reasons
- It has a good amount of ROM and External RAM memory
- It provides external RAM ~_^ which I love
- Some issues with earlier MBC controllers like 3 unusable banks are all fixed
- It's extremely well documented and known
- It certified to work fully and accurately with the GBC
There are better ones out there, some I'd love to use, but documentation is scarce, implementation is poor and/or theres awesome features that are missing. MBC5 I find is the best middle ground.
Note: Version 1 Used an MBC3 for the timer but after careful re-consideration I've moved to MBC5 for points 1 and 5 mentioned above.
What's in it so far
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Bank switching capability including even cross bank jumping and calling even to and/or from sram
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Simple graphics system which I plan to expand that can print individual tiles at certain locations or a string of tiles at one location onward. It does need expanding.
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MBC controlling capability from small stuff like controlling the individual aspects of MBC to large stuff like formatting and initializing the SRAM.
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Various code for a basic game loop, dma routine that installs in HRAM, LCD code, joypad code, memory code like formatting memory, and startup code. It also contains a lot of constants and macros to make things easier.
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Initial structuring of the memory and ROM
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A newly revised sample tileset I made which contains many ascii and extended ascii characters. The fontset was entirely created by me and is a great improvement over the first version. It's licensed CC-BY for anyone to use in any project with attribution.
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Full Interrupt Implementation including HBlank, LCDC, LYC, Serial, Timer, and of course VBlank. There's also smart DMA copying / Joypad updating making use of the interrupt system.
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Comprehensive joypad code with macros simplifying all aspects of it
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Timer functionality in 1/17th seconds, 0.25 seconds, seconds, minutes, hours, and days to add code into.
Optimizations and Some extra features
1st Byte of bank indicates bank number
A single byte is placed at the start of each rom and external ram bank that indicates the bank number. While this seems simple or redundant it skips the need to track which bank your on in memory and it's relatively easy to always read it out fairly quickly and accurately in one line cutting various code and memory usage as well as simplifying things.
External RAM Formatting
- Contains the first byte bank number mentioned above
- Contains a small hex signature which it uses to verify if the external ram is formatted for the first time or not. If the signature is missing or invalid then it's cue the external ram needs formatting and does so on boot.
- Contains a version code for compatibility, now this may seem kind of weird for a gameboy rom as usually it's read-only memory in a cart however in the modern world where most people load up an emulator it can be nice to "update" the game by downloading the latest update and it not mess up the save file for example. The save file will contain the version code of it's data and the game could work around that in compatibility or "upgrade" the save file while preserving the save data. Basically a modern touch option on the old classic that can totally be ignored or removed with ease.
How do I compile? What do I need?
All your answers are in the COMPILE.md file from what to install, how and where
to get it, to compiling. The super short version though is use rgbds and run
./scripts/build.sh any more elaboration can all be found in the seperate file
COMPILE.md.