Demo code for sending UDP datagrams from a Logitech Attack 3 joystick to a Roomba iRobot Create

gamepad-control.js

var GamePad = require( 'node-gamepad' );
var dgram = require( 'dgram' );
var controller = new GamePad('logitech/attack3');
controller.connect();

var socket = dgram.createSocket('udp4');

socket.on('listening', function(){
    socket.setBroadcast(true);
});

socket.bind(9000);

function map_u(x, in_min, in_max, out_min, out_max) {
    return (x - in_min) * (out_max - out_min) / (in_max - in_min) + out_min;
}

function constrain_u(x, min, max) {
    if (x < min) return min;
    else if (x > max) return max;
    return x;
}

function cmap_u(x, in_min, in_max, out_min, out_max) {
    return constrain_u(map_u(x, in_min, in_max, out_min, out_max), out_min, out_max);
}

function fletcher16(buf) {
    var sum1 = 0xff, sum2 = 0xff;
    var i = 0;
    var len = buf.length - 2;

    while (len) {
      var tlen = len > 20 ? 20 : len;
      len -= tlen;
      do {
        sum2 += sum1 += buf[i++];
      } while (--tlen);
      sum1 = (sum1 & 0xff) + (sum1 >> 8);
      sum2 = (sum2 & 0xff) + (sum2 >> 8);
    }
    /* Second reduction step to reduce sums to 8 bits */
    sum1 = (sum1 & 0xff) + (sum1 >> 8);
    sum2 = (sum2 & 0xff) + (sum2 >> 8);
    return sum2 << 8 | sum1;
}

// Buffer for packet data
var buf = new Uint8Array(14);

// Initialize
buf[0] = 0xFE;
buf[1] = 0xED;

buf[2] = 0x02; buf[3] = 0x00;
buf[4] = 0x02; buf[5] = 0x00;
buf[6] = 0x02; buf[7] = 0x00;
buf[8] = 0x02; buf[9] = 0x00;
buf[10] = 0x00;
buf[11] = 0x00;
buf[12] = 0;
buf[13] = 0;


controller.on('stick:move', function(obj) {
    var valx = 1023 - cmap_u(obj.x, 0, 255, 0, 1023);
    var valy = cmap_u(obj.y, 0, 255, 0, 1023);
    buf[2] = (valx & 0xFF00) >> 8;
    buf[3] = (valx & 0x00FF);

    buf[4] = (valy & 0xFF00) >> 8;
    buf[5] = (valy & 0x00FF);

} );

controller.on( '1:press', function() {
    buf[10] = 0xFF;
} );

controller.on( '1:release', function() {
    buf[10] = 0x00;
} );

controller.on( '2:press', function() {
    buf[11] = 0xFF;
} );

controller.on( '2:release', function() {
    buf[11] = 0x00;
} );


setInterval(function () {
	var checksum = fletcher16(buf);
    buf[12] = (checksum & 0xFF00) >> 8;
    buf[13] =  checksum & 0x00FF;
    buf[0] = 0xFE;
    buf[1] = 0xED;

    out = Array(14);
    for (i = 0; i < buf.length; i ++) {
        out[i] = Number(buf[i]).toString(16);
    }

    console.log(out);

    socket.send(buf, 0, buf.length, 9000, "192.168.0.255");
}, 100)

logitech-attack3.json

{
    "vendorID": 1133,
    "productID": 49684,
    "joysticks": [
        {
            "name": "stick",
            "x": {
                "pin": 0
            },
            "y": {
                "pin": 1
            }
        }
    ],
    "buttons": [
        {
            "value": 1,
            "pin": 3,
            "name": "1"
        },
        {
            "value": 2,
            "pin": 3,
            "name": "2"
        }
    ]
}