writing a value:
function(r, g, b) {
var buffer = new Uint8Array([
0xaa, 0x0a, 0xfc, 0x3a, 0x86, 0x01, 0x0d,
0x06, 0x01, r, g, b, 0x00, 0x00,
(Math.random() * 1000) & 0xff, 0x55, 0x0d
]);
for (var i = 1; i < buffer.length - 2; i++) {
buffer[15] += buffer[i];
}
return buffer;
}