Apple Desktop Bus

For my first real project with the teensy I'm going to try to get the Apple Desktop Bus protocol working. That should let me connect via USB, my really nice old Apple ][ keyboard (which sadly is missing two keys), mouse, game-pad and an old wacom tablet!

There's some docs the protocol here:

• ADB - The Untold Story: Space Aliens Ate My Mouse

 and a pinout of the connector cable on wikipedia:

So I cut open a connector and soldered it onto headers to plug into my breadboard:

Then I checked which color wires were which pins using continuity testing mode of my multimeter.

Then designed the following circuit:

So the idea behind this is that the +5V part will be using USB to power the keyboard and mouse, this will not go through the AVR microchip as you can see from the diagram here, USB1 connects straight up to the +5V pin without going through the chip.

I thought about whether or not I needed a pull-up resistor, based on sparkfun tutorial and I think that I don't need one. I need to double check that ADB devices ground the zero rather than leave it floating - maybe this relates to conflict detection.

The data pin of the ADB socket is connect through a 10k ohm resistor to limit the current and make sure that no damage is done to the chip.

I carefully continuity-tested the ADB socket plugged into the breadboard to make sure it has no shorts (and to double-check against the pinout)