Homebridge plugin that pretends to be a lightbulb to allow you to send arbitrary commands out a serial port, e.g., to an Arduino. Set up config.json with your messages and device; the messages will be mapped to intervals between 0 and 100. E.g., if you have two messages, the first will be sent by setting the brightness of this "bulb" to anything between 0 and 50, and the second by setting the brightness to 50-100.
This allows you to create more or less arbitrary HomeKit commands by defining scenes that set this brightness value. For example, I have an HDMI switch controlled by an Arduino, and two HomeKit scenes to switch between different inputs: "TV Mode" is brightness to 25%, "Nintendo Mode" is brightness to 75%.
Thanks to StatefulDummySwitch for the simple example plugin.
Example config.json:
...
"accessories": [
{
"accessory": "SerialSwitch",
"name": "Projector",
"device": "/dev/cu.usbserial-DC008MZU",
"messages": ["1", "2"]
}
]
...