Hacking an Apple Extended Keyboard II Apr. 2nd, 2016 Matthew Grill

Hacking an Apple Extended Keyboard II

April 2nd, 2016

You might have heard me preach the benefits of using a mechanical keyboard. They offer sharp and precise keystrokes, high degree of customization, reliability and a lengthy lifespan. Most mechanical keyboards are offered with a Windows-only layout, missing the CMD key and a potentially flipped control and option key. I didn’t want to deal with those issues again, and after having waffled for a few months on getting a new keyboard, I found an Apple Extended Keyboard II, AEK2, on Ebay and bought it. Shipping included it was cheaper than most decent mechanical keyboards, and actually looked like it belonged, no key remapping required.

The only issue with using a keyboard manufactured in the early 90’s, no USB. At the time Apple was shipping keyboards with ADB, Apple Desktop Bus. There are a few off the shelf solutions to convert ADB to USB, but most have been discontinued or are ridiculously expensive. There is also the DIY solution, which I’ll cover in this post.

You’ll need the following components to make this possible,

  • Teensy 2.0
  • 1k Ohm resistor
  • Some wire
  • A system capable of programming a USB based microcontroller, your computer should work just fine

Depending on how you decided to wire the Teensy up, you can keep everything internal to the keyboard, or slice up the ADB cable[1]. Connect ADB pin 1 (Data) to Teensy pin D0, pin 3 to Teensy VCC (5v), and pin 4 to Teensy GND (Ground).

Additionally, that resistor, wire it up like so,

Once you’ve completed the wiring, clone tmk_keyboard and maneuver to converter/adb_usb. If you’re using the Teensy you can just execute, make -f Makefile.teensy[2]. Once the .hex file has been created, download the Teensy Loader application, hook up your Teensy, and flash the newly created firmware. After the Teensy reboots, you should have a new keyboard!

[1] Really just mini-DIN cable, S-Video.
[2] Xcode command line tools and/or brew should sort that.