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RetroAdapter

Originally written by Paul Qureshi (for the ATmega168 microcontroller).

Modifications in this repository by Denilson Sá (adapted to the ATmega8 microcontroller).

Overview

This repository contains my changes on top of RetroAdapter (originally for ATmega168) to make it work with the ATmega8 microcontroller that I already had. This is basically the RetroAdapter version 2.1a with these changes:

  • some tweaks in the Makefile,
  • an updated usbdrv,
  • some bugfixes in the main firmware (corrected some button mappings),
  • many modules disabled (because I'll never use them, and to reduce the size of the firmware),
  • a few conditionals hardcoded (because my hardware only supports one kind of controller),
  • optional bootloader changed (or updated) from bootloadHID to USBaspLoader.

The firmware in this repository worked on the ATmega8 microcontroller.

Feel free to use this repository as a starting point for your own project.

Background

For a long while I wanted to build a Sega Mega Drive controller adapter to USB. Fortunately, Paul Qureshi wrote have created RetroAdapter and published all the source and schematics on his website http://denki.world3.net/retro_v2.html. This adapter uses an ATmega 8-bit microcontroller with almost no extra components (only a few resistors, a few capacitors, a couple of Zener diodes, a crystal).

He used ATmega168, which is more powerful than the ATmega8 that I already have. In order to make it compile and make it fit in 8KB (or 6KB + bootloader), I had to make small changes to the RetroAdapter code. These changes are saved in this repository.

The Makefile changes mostly come from my previous project: atmega8-magnetometer-usb-mouse

My blog post about this project: http://denilson.sa.nom.br/blog/2013-07-15/i-built-a-retroadapter

How to get started

If you're not familiar with AVR ATmega microcontrollers, please read my multi-part series: First contact with ATmega8 microcontroller. It starts from the very basics and goes step by step on building a simple project using such microcontrollers.

Once you're familiar with AVR ATmega microcontrollers, and you have the necessary software tools, you can dig into this repository:

  • fuses.md - Lists what are the expected Fuse values to be programmed into the microcontroller.
  • hardware/ - Schematics of the original RetroAdapter and also for the ATmega8 version.
  • source/ - The entire source-code for the firmware and for the optional bootloader. Includes a Makefile which can be used to build the firmware, write it to the microcontroller, and also write the fuse bytes.
  • more_docs/ - Further documentation on the RetroAdapter, saved from the original website before it went offline.
  • legacy_from_RetroAdapter_2.1a/ - Other files originally from RetroAdapter 2.1a, before the changes from this repository. You probably don't need these.