This one has fewer features than most others because the goal is to make it basic enough that LUFA and an ATmega32U4 can do all the work.
Any of these boards should work.
- Arduino Leonardo / Micro.
- Sparkfun Pro Micro.
- Adafruit Atmega32u4 breakout.
- Teensy 2.0.
- A-Star 32U4 Micro.
A 5V inverter is needed so that the MCU's UART can process the keyboards 1200 baud, which while TTL level is idle low like RS232. I used a 7404.
The 8-pin DIN is connected as follows.
| Connector | Signal | Pin | Arduino | Color |
|---|---|---|---|---|
| 1 | GND | GND | GND | brown |
| 2 | GND | GND | GND | white |
| 3 | +5V | VCC | 5V | black |
| 4 | MOUSE | N/C | blue | |
| 5 | RX | PD3 (*) | TX (1) | green |
| 6 | TX | PD2 (*) | RX (0) | yellow |
| 7 | POWER | PD0 | 3 | orange |
| 8 | +5V | VCC | 5V | red |
(*) Keyboard RX goes to 1Y of the inverter and 1A to AVR TX. Keyboard TX goes to 2A of the inverter and 2Y to AVR RX.