This firmware converts the protocol of Apple Macintosh keyboard **M0110**, **M0110A** and **M0120** into USB. Target of this project is USB AVR controller **ATmega32U4**. Using this converter you can revive these retro keyboards with modern computer.
You need **4P4C** cable and **ATMega32U4** board like PJRC [Teensy]. Port of the MCU `PD1` is assigned to `CLOCK` line and `PD0` to `DATA` by default, you can change pin configuration with editing `config.h`.
You may need pull-up resistors on signal lines(`CLOCK`, `DATA`) in particular when you have long or coiled cable. **1k-10k Ohm** will be OK for this purpose. In that case the converter may not read signal from keyboard correctly without pull-up resistors.
You can use [PJRC HID listen](http://www.pjrc.com/teensy/hid_listen.html) to see debug output. The converter has some functions for debug, press `<Command>+H` simultaneously to get help.