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Gameboy Release Guide

Converting MIDI files into a playable music Gameboy cartridge involves several steps, including preparing your MIDI files, converting them into a format compatible with the Gameboy’s sound hardware, assembling a Gameboy ROM, and finally flashing the ROM onto a physical cartridge. Below is a detailed, step-by-step guide to help you through the process.

Prerequisites

Before you begin, ensure you have the following:

A MIDI file that you wish to convert.
A computer with the ability to run the necessary software (Windows, macOS, or Linux).
Basic knowledge of command-line operations and programming concepts.
Hardware: A programmable Gameboy cartridge (e.g., Everdrive GB, EMS 64M USB Cartridge) and a Gameboy console for testing.

Step 1: Prepare Your MIDI File

1. Simplify the MIDI File to Four Channels

The original Gameboy has only four audio channels:

Channel 1: Square wave (melody)
Channel 2: Square wave (harmony)
Channel 3: Programmable wave (bass or additional melody)
Channel 4: Noise (percussion)

Use a MIDI editor to reduce your MIDI file to these four channels. Assign instruments accordingly and ensure each channel is monophonic (one note at a time).

Recommended MIDI Editors:

Anvil Studio (Windows)
MuseScore (Windows, macOS, Linux)
LMMS (Windows, macOS, Linux)

Step 2: Install DefleMask Tracker

1. Download DefleMask

Visit DefleMask Official Website.
Download the version suitable for your operating system.

2. Install and Set Up DefleMask

Install DefleMask following the on-screen instructions.
Open DefleMask and set the target system to Game Boy:
- Go to File > New Project.
- Select Nintendo Game Boy from the list.

Step 3: Import and Edit MIDI in DefleMask

1. Import MIDI File

In DefleMask, go to File > Import MIDI.
Select your simplified MIDI file.
Map each MIDI track to the appropriate Gameboy channel.

2. Adjust Instruments and Effects

Use DefleMask’s instrument editor to assign Gameboy-compatible instruments.
Adjust volume levels and effects to match the Gameboy’s sound capabilities.

3. Test the Music

Press the Play button to listen to your track within DefleMask.
Make necessary adjustments to improve sound quality and compatibility.

Step 4: Export the Music Module

1. Export from DefleMask

Go to File > Export Module.
Choose the .mod format, which is compatible with the GBT Player converter.

Note: If the .mod format isn’t compatible, consider exporting to DefleMask’s own .dmf format and using alternative conversion tools.

Step 5: Install GBT Player

1. Download GBT Player

Visit the GBT Player GitHub Repository.
Download or clone the repository to your computer.

2. Install GBT Player

Extract the downloaded files to a directory on your computer.
Familiarize yourself with the contents, especially the mod2gbt converter and gbt_player.s source file.

Step 6: Convert the Module to GBT Format

1. Use the mod2gbt Converter

Open a command prompt or terminal window.
Navigate to the directory containing mod2gbt.

2. Run the Conversion Command

mod2gbt your_song.mod your_song.gbt

Replace your_song.mod with the path to your exported module.
This command generates your_song.gbt.asm, which contains the music data for the Gameboy.

Step 7: Set Up the Gameboy Development Environment

1. Install RGBDS

Download RGBDS (Rednex Game Boy Development System) from the RGBDS GitHub Repository.
Follow the installation instructions specific to your operating system.

2. Create Your Project Structure

Create a new directory for your Gameboy project.
Inside, create subdirectories like src for source code and music for music data.

Step 8: Integrate GBT Player and Music Data

1. Copy Necessary Files

Place gbt_player.s into your src directory.
Move your_song.gbt.asm into your music directory.

2. Write the Main Assembly Code

Create a file named main.asm in your src directory with the following content:

SECTION "Main", ROM0[$0100]

Start:
    nop
    jp Init

Init:
    LD SP, $FFFE
    DI
    ; Initialize sound hardware here
    LD HL, your_song_Data
    LD A, 0  ; Bank number if needed
    CALL gbt_init
    EI

MainLoop:
    HALT
    JP MainLoop

VBlankISR:
    PUSH AF
    PUSH BC
    PUSH DE
    PUSH HL
    CALL gbt_update
    POP HL
    POP DE
    POP BC
    POP AF
    RETI

SECTION "Interrupt Vector", ROM0[$0040]
    JP VBlankISR

INCLUDE "gbt_player.s"
INCLUDE "../music/your_song.gbt.asm"

Ensure that your_song_Data matches the label in your music data file.

Step 9: Compile the Gameboy ROM

1. Create a Build Script

For Windows (build.bat):

@echo off
rgbasm -o main.o src\main.asm
rgblink -o game.gb main.o
rgbfix -v -p 0 game.gb

For Unix-based systems (build.sh):

#!/bin/bash
rgbasm -o main.o src/main.asm
rgblink -o game.gb main.o
rgbfix -v -p 0 game.gb

2. Run the Build Script

Execute the script to compile your project.
The output will be a game.gb ROM file.

Step 10: Test the ROM in an Emulator

1. Choose an Emulator

BGB (Windows): Download BGB
SameBoy (Windows, macOS, Linux): Download SameBoy

2. Load and Test the ROM

Open the emulator and load game.gb.
Verify that the music plays correctly.
If issues arise, revisit previous steps to troubleshoot.

Step 11: Flash the ROM onto a Gameboy Cartridge

1. Obtain a Flash Cartridge

Purchase a flashable cartridge like:
- Everdrive GB
- EMS 64M USB Cartridge
- BennVenn’s El Cheapo SD

2. Install Cartridge Software

Install any necessary drivers and software provided by the cartridge manufacturer.

3. Flash the ROM

Connect the cartridge to your computer via USB or another interface.
Use the provided software to write game.gb to the cartridge.

Step 12: Play the Cartridge on a Gameboy

1. Insert the Cartridge

Place the flashed cartridge into your Gameboy console.

2. Test the Music

Turn on the Gameboy.
Confirm that the music plays as intended on the actual hardware.

Additional Tips

Hardware Limitations: Remember that the Gameboy’s audio hardware is limited. Complex MIDI files may require significant simplification.
Alternative Tools: If you encounter issues with DefleMask, consider using other trackers like OpenMPT or FamiTracker, though additional conversion steps may be necessary.
Community Support: Engage with communities like ChipMusic.org or the Gameboy Dev Discord for assistance.
Legal Considerations: Ensure that you have the rights to distribute any music you convert, especially if the MIDI files are of commercial songs.

By following these steps, you can successfully convert MIDI files into a playable music Gameboy cartridge. This process not only allows you to enjoy custom music on original hardware but also provides a hands-on experience with retro console development.