Communication with a bulb is done via the service f815e810456c6761746f4d756e696368 and its characteristic f815e811456c6761746f4d756e696368.
The first byte in the protocol is the command, the others are the payload. When sending a command without payload the current value from this command is send back as notification.
- 0x35: Color
- 0x58: User defined name of the bulb
- 0x57: Brightness
The color is defined by these four variables: white, red, green, blue. Each variable has a value between 0 and 4095 (0xfff).
The byte sequence, which has to be send to bulb can be computed on the following way:
For example we set the color to w: 0xaaa, r: 0xbbb, g:0xccc, b:0xddd, with a fading of 0x111 we send:
35 |
11 01 |
0a 00 |
aa 8a |
bb 3b |
cc 2c |
dd 1d |
|---|---|---|---|---|---|---|
| Color command | fading in LE | unkown | white with 8 as prefix | red with 3 as prefix | green with 2 as prefix | blue with 1 as prefix |
To compute the color part the following js function is used:
const buffer = new Buffer(8);
buffer.writeUInt16LE(this.white | 0x8000, 0);
buffer.writeUInt16LE(this.red | 0x3000, 2);
buffer.writeUInt16LE(this.green | 0x2000, 4);
buffer.writeUInt16LE(this.blue | 0x1000, 6);The color send back through the notification has a different format. For the same values as set above the following bytes are received:
35 |
da 0a |
5e 1d |
57 2c |
4f 3b |
aa 0a |
dd 1d |
cc 2c |
bb 3b |
|---|---|---|---|---|---|---|---|---|
| Color command | current white (0xada) |
current blue (0xd5e) |
current green (0xc57) |
current red (0xb4f) |
target white (0xaaa) |
target blue (0xddd) |
target green (0xccc) |
target red (0xbbb) |
// command code byte already stripped
// these are the current colors of the lamp.
let white = buffer.readUInt16LE(0);
let blue = buffer.readUInt16LE(2) ^ 0x1000;
let green = buffer.readUInt16LE(4) ^ 0x2000;
let red = buffer.readUInt16LE(6) ^ 0x3000;
// these are the colors the lamp is fading to.
let whiteTarget = buffer.readUInt16LE(8);
let blueTarget = buffer.readUInt16LE(10) ^ 0x1000;
let greenTarget = buffer.readUInt16LE(12) ^ 0x2000;
let redTarget = buffer.readUInt16LE(14) ^ 0x3000;The name is received as a null terminated string. For example: 0x58 0x45 0x6c 0x67 0x61 0x74 0x6f 0x20 0x41 0x76 0x65 0x61 0x00 = Elgato Avea
Brightness goes from 0-4095 and is send and received as little endian value.
e.g. 0x57ff0f for 4095.