The Overdrive Cart is a flash cart for running homebrew games with a bunch of extra features for expanding the capabilities of the Virtual Boy.

This is a work in progress.

Features

• Flash cart with support for up to 128 megabit (16 megabyte) roms, which is the max supported by the Virtual Boy address space
• Wireless internet connectivity
• Built-in dashboard to manage, download and run games, provide matchmaking for supported games, and other such things typically found on a modern game console
• Support for save game cloud syncing
• Support for “Overdrive Games” — games that leverage the more powerful hardware hiding within the cartridge.
• Support for “enhanced” games — games that run on the standard VB hardware but can take advantage of expanded capabilities if the overdrive cart is detected (such as internet play)
• Debug tools for homebrew development, such as:
  • One-click ROM flashing
  • Streaming I/O for outputting debug data to the development machine (or injecting debug data the other way)
  • Profiling
  • Tracing
  • Trapping

Approach

At a high level, I am basically going to hide a Raspberry Pi Zero 2 W in the cartridge and have it behave like a VB cartridge whose contents is always changing. The concept is simple enough (some might even say boring), but actually getting there has been sufficiently challenging.

So, why use a Raspberry Pi Zero 2 W?

• It fits in the VB cartridge (it’s tight, but it does fit)
• It has Wifi
• It has just enough GPIO pins to do what we need
• It has a graphics accelerator (for “overdrive” games)
• It is inexpensive (one of the least expensive parts required for the build, actually)
• It is low-power enough that it can be powered by the cartridge pins without needing an external supply

Project Status

I have prototype hardware that can:

• Flash ROMS using a command-line program
• Stream data into and out of the ROM that is executing
• Output profiling data
• Run “overdrive” games, including passing controller input back to the overdrive program

What’s still missing:

• Support for sound originating from the VB’s VSU (currently output from the SBC is supported though)
• An “operating system” that allows you to do tasks using the VB’s controller, such as loading or finding new homebrew, managing saves, connecting to the internet, etc.
• Server support for internet play and cloud game saves
• Proper client libraries for internet play and other such enhancements so that games other than my own can make use of these capabilities
• A housing for the cartridge (currently it’s just a PCB hanging out of the VB)

Gallery

Hardware

Demos

Command-line flashing

“Overdrive” application, using coprocessor rendering

   

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