This is a tiny sketch that lets you control NeoPixels over I2C. It was originally designed for a project where a Raspberry Pi needed to control a bunch of LEDs but was busy doing other things.

It's designed for the Trinket M0 but will probably run on just about anything.

It's simple!

1. Acquire some sort of board you can program with the Arduino IDE. I suggest a Trinket M0.
2. Install the Adafruit NeoPixel Library by opening your Arduino IDE and going to Sketch -> Include Libraries -> Manage Libraries...
3. verify that I2C_ADDRESS is set to a usable value. It defaults to 0x45 but maybe you have a device on that address already?
4. set NEOPIXEL_PIN, NEOPIXEL_COUNT, and NEOPIXEL_TYPE to match your setup
5. (optional) configure default values for colorCorrection and brightness
6. flash your board!

By default the device is on i2c address 0x45. It's controlled via a simple protocol which consists of a command byte and (optionally) additional bytes as arguments. See Protocol Reference below for details.

Note: the command parser is intentionally very simple. It looks at the first byte of the message and dispatches to a handler that may or may not read additional bytes. When the handler is done the buffer is flushed. This means that you must send each command in a single, self-contained i2c message. This works for me but may be a bad idea; please open an issue if you have objections.

You can enable and disable quick-and-dirty color correction using the 0x03 and 0x04 commands, respectively. The gamma table is precalculated for your convenience. See this page for more information. Color correction is disabled by default.

Copyright (c) 2019 Ben Bleything

Released under the terms of the MIT License; see LICENSE for details.