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Game Gear Release Guide

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

Important Legal and Safety Considerations

Homebrew Development: Developing and using homebrew software on the Sega Game Gear is generally acceptable, but ensure you are not infringing on any copyrights.
Legal Compliance: Use only original music or music you have the rights to distribute. Do not use this guide for piracy or any illegal activities.
Proceed with Caution: Flashing hardware involves risks. Follow instructions carefully and understand each step before proceeding.

Prerequisites

Before you begin, ensure you have the following:

A MIDI file that you wish to convert.
A computer capable of running the necessary software (Windows, macOS, or Linux).
Basic knowledge of programming concepts and command-line operations.
Sega Game Gear Development Tools:
- WLA-DX assembler for Z80 CPU.
- Emulators: Such as Emulicious or Fusion for testing.
Audio Tools:
- DefleMask Tracker: A cross-platform tracker for chiptune music creation.
Hardware:
- Programmable Game Gear Cartridge: Such as EverDrive GG.
- Sega Game Gear Console for testing.
- SD Card: To transfer files between your computer and the Game Gear cartridge.

Step 1: Prepare Your MIDI File

1. Simplify the MIDI File

The Sega Game Gear has specific audio capabilities:

Sound Chip: Texas Instruments SN76489 PSG (Programmable Sound Generator), similar to the Sega Master System.
Audio Channels:
- 3 Square Wave Channels: For melody and harmony.
- 1 Noise Channel: For percussion.

Use a MIDI editor to tailor your MIDI file for the Game Gear:

Reduce the number of simultaneous instruments to fit within the 4 available channels.
Assign instruments appropriately, considering the square wave and noise capabilities.
Ensure each MIDI track corresponds to a sound channel on the Game Gear.

Recommended MIDI Editors:

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

Step 2: Install DefleMask Tracker

1. Download DefleMask

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

2. Install and Set Up DefleMask

Install DefleMask following the provided instructions.
Open DefleMask and set the target system to Sega Master System:
- Go to File > New Module.
- Select Sega Master System from the list.

Note: The Sega Game Gear and Master System share the same sound hardware, so you can use the Master System setting in DefleMask.

Step 3: Import and Edit MIDI in DefleMask

1. Import MIDI File

DefleMask does not support direct MIDI import, so you’ll need to convert your MIDI file to a format that can be imported, or manually input the notes.

Alternative Method Using MIDI2MOD:

Convert MIDI to MOD Format:
- Use a tool like OpenMPT to import your MIDI file and export it as a .mod file.
Import MOD into DefleMask:
- In DefleMask, go to File > Import Module.
- Select your .mod file.

Note: Be aware that importing MOD files into DefleMask may require adjustments due to differences in supported features.

2. Manually Input Notes

If importing is not feasible, manually transcribe your MIDI tracks into DefleMask.
Use the piano roll or pattern editor to input notes for each channel.

3. Map Tracks to Game Gear Channels

Assign each track to one of the 4 PSG channels.
Adjust instruments to use square waves for melodic channels and noise for percussion.

4. Edit the Song

Fine-tune notes, volumes, and effects to match the Game Gear’s capabilities.
Use DefleMask’s instrument editor to create square wave instruments.

5. 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 Data

1. Export from DefleMask

Go to File > Export.
Choose VGM Format (*.vgm) as the export format.
Save the file as your_song.vgm.

Note: The VGM (Video Game Music) format is suitable for the Game Gear’s sound chip.

Step 5: Convert VGM to PSG Data

The Game Gear cannot directly play VGM files; you need to convert the VGM data into a format compatible with a sound driver that can be used in your Game Gear program.

1. Use VGM2PSG or Custom Tools

Since there are limited tools for Game Gear development, you may need to use or create a custom tool to convert VGM to data arrays.

2. Alternative Method: Use a Sound Driver

SCC Sound Driver: A sound driver that can play PSG data on the Game Gear.
Telenet Sound Driver: Another option for PSG playback.

Note: Due to the limited resources, you may need to write or adapt a sound driver for your project.

Step 6: Install WLA-DX Assembler

1. Download WLA-DX

Visit the WLA-DX GitHub Repository.
Download the latest release suitable for your operating system.

2. Install WLA-DX

Install WLA-DX following the provided instructions.
Ensure the wla-z80 assembler is accessible from your command line.

Step 7: Set Up Your Project

1. Create Project Directories

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

2. Place Music Files

Move your converted music data file into the music directory.

Step 8: Write the Main Program

1. Create main.asm in the src Directory

    .include "wla.inc"

    .org $0000

Start:
    di          ; Disable interrupts
    ld sp, $dff0 ; Set stack pointer

    call InitSound

MainLoop:
    call UpdateSound
    jp MainLoop

; Sound Initialization
InitSound:
    ; Initialize sound hardware
    ; Load music data
    ret

; Sound Update Routine
UpdateSound:
    ; Update sound playback
    ret

    .org $0038
InterruptHandler:
    reti

    .bank 0
    .org $0000
    .include "../music/music_data.inc"

    .org $FFFC
    .dw Start      ; Reset vector

Notes:
- You’ll need to implement the InitSound and UpdateSound routines to handle sound playback.
- Include your music data file in the assembly code.

2. Include Music Data

In your main.asm, include the music data file:
```
.include "../music/your_song_data.inc"
```
Ensure that the paths to the included files are correct.

Step 9: Compile the ROM

1. Create a Build Script

Create a build.bat (Windows) or build.sh (macOS/Linux) script in your project directory.

Sample Build Script (build.sh):

#!/bin/bash
# Assemble the code
wla-z80 -o main.o src/main.asm

# Link the object file into a ROM
wlalink -d -S linkerfile main.gg

2. Create a Linker File (linkerfile):

[objects]
main.o

[output]
main.gg

3. Run the Build Script

Open a terminal in your project directory.
Make the script executable:
```
chmod +x build.sh
```
Run the script:
```
./build.sh
```
This should produce main.gg, your Game Gear ROM file.

4. Troubleshooting

If errors occur, check your assembly code and included files.
Ensure all paths and filenames are correct.
Verify that WLA-DX is correctly installed and accessible.

Step 10: Test the ROM in an Emulator

1. Choose an Emulator

Emulicious (Windows, macOS, Linux): Download Emulicious
Fusion (Windows): Download Kega Fusion
MEKA (Windows, Linux): Download MEKA

2. Load and Test the ROM

Open the emulator and load main.gg.
Verify that the music plays and the ROM functions correctly.
Use debugging tools if the emulator provides them.

Step 11: Flash the ROM onto a Game Gear Cartridge

1. Obtain a Flash Cartridge

EverDrive GG: Available from Krikzz

2. Prepare the ROM

Ensure your ROM is compatible with the flash cartridge.
Some flash carts may require the ROM to have a specific header or format.

3. Transfer the ROM

Copy main.gg to the SD card used by your flash cartridge.
Insert the SD card into the cartridge.

Step 12: Play the Cartridge on a Game Gear Console

1. Insert the Cartridge

Place the flash cartridge into your Sega Game Gear console.

2. Load and Test the ROM

Turn on the Game Gear.
Use the flash cartridge’s menu to select your ROM.
Confirm that the music plays as intended on actual hardware.

Additional Tips

Understanding the Game Gear’s Audio Hardware
- The SN76489 PSG generates simple tones; understanding its limitations helps in creating better music.
- Each of the 3 tone channels can produce square waves at different frequencies.
- The noise channel can generate different types of noise suitable for percussion.
Optimize Audio Quality
- Since the Game Gear’s audio hardware is limited, composing effective chiptune music requires creativity within constraints.
- Use DefleMask’s instrument editor to adjust waveforms and envelopes.
Use Existing Sound Drivers
- If writing your own sound driver is challenging, look for open-source Game Gear projects that include sound drivers you can adapt.
Community Resources
- SMS Power!: smspower.org - A community dedicated to Sega Master System and Game Gear development.
- DefleMask Community: Engage with other chiptune composers for tips.
Legal Considerations
- Only use music that you have the rights to distribute.
- Be cautious of licensing when using samples or reproducing existing songs.

Summary

By following these steps, you can successfully convert MIDI files into a playable music Sega Game Gear cartridge:

Prepare and simplify your MIDI file to match the Game Gear’s audio capabilities.
Install DefleMask Tracker and import/edit your music, creating Game Gear-compatible instruments.
Export your music as a VGM file and convert it to a format compatible with your sound driver.
Install WLA-DX assembler and set up your project, including the music data.
Write a simple program to play your music using sound routines.
Configure the build script and assemble your ROM using WLA-DX.
Test your ROM in an emulator to verify functionality.
Flash the ROM onto a physical cartridge using hardware like the EverDrive GG.
Play the cartridge on an actual Game Gear console to enjoy your custom music.

This process allows you to experience custom music on your Sega Game Gear console and provides valuable experience in retro console development.

Disclaimer: Modifying your Sega Game Gear console and creating custom cartridges involves risks and may be subject to legal restrictions in some jurisdictions. Always ensure you are complying with local laws and do not engage in piracy or distribute copyrighted material.