Arduino code and Pygame host for a Macintosh (non-ADB) keyboard
This project emulates a Macintosh Plus-compatible keyboard using any Serial-capable Arduino. It won't replace an original keyboard, but it should suffice for most basic purposes. It emulates every feature of the original keyboard, including the arrow keys but excluding the keypad.
Some code in this project is based on Tomek Rekawek's
mac-plus-ps2 project,
which interfaces a PS/2 keyboard to the Mac through an Arduino. It is
probably less laggy and more reliable than my code, which uses some
functions from mac-plus-ps2.
The root directory of the repository is a PlatformIO project,
configured for the metro target, so it should run on any
Uno-compatible board without change. You can also change the target in
platformio.ini for any other Arduino board. Usage is simple: connect
a keyboard cable, upload the sketch, and run the host Python script.
The data and clock Arduino pins can be changed with the #defines at
the top of src/mac-plus-serkey.cxx if desired. The defaults are as
follows:
| Mac pin | Arduino pin |
|---|---|
| Ground | Ground |
| Clock | Pin 2 |
| Data | Pin 3 |
| +5V | unconnected |
The Mac's 5 volt supply stays disconnected for two reasons: one, we don't want to draw more power from it than needed, and two, the Arduino will receive USB power from the computer.
Connect the Arduino, Mac, and the host computer together in any order. The order doesn't matter, as the Arduino will "synchronize" with the Mac and the host script works independent of both.
The script is in Python 3. It depends on
pyserial and
pygame, so install those before running
it. Then, run the pygame_host.py script, which requires one
positional argument: the serial port to send keystrokes to. It must be
run from the command line. For example, assuming python is Python 3:
$ python pygame_host.py /dev/ttyUSB0
The window that appears is the keyboard window. Only keys pressed while that window is active will be sent to the Arduino and subsequently to the Mac.
I have tested the script and entire system on Arch Linux and Windows, and it worked fine on both. I have not tested it on any variety of macOS.
The computer's keyboard is mapped more or less character-for-character to the Mac Plus keyboard. The variations to fit the Mac keyboard are as follows:
- Left and right Ctrl are Option
- Left and right Alt are Command
- Caps Lock emulates the physical key-locking behavior of the original keyboard
- Enter (which is not present on the Mac Plus keyboard except on the keypad, but is present on the original Mac keyboard) is mapped to both numpad Enter and the Delete key.
- Subsequently, the Mac's Return key is mapped to the computer's Enter.
The current Caps Lock status is visible in the keyboard window's title.
Caps Lock can also be remapped to one of two other keys with optional command-line flags:
| Option | Operation |
|---|---|
-o/--caps-is-option |
remap Caps Lock to Option |
-c/--caps-is-command |
remap Caps Lock to Command |
This project will never replace the real keyboard. It is generally laggy and skips keystrokes at high speed. This could probably be fixed, but I don't know how or even what's causing that.
One particular symptom this project exhibits is that the lag time and reliability seem to decline the longer the Arduino is plugged in. I don't know why this is, but it can be resolved by unplugging and reinserting the Arduino, and restarting the Python host accordingly.