Make a Lego Mindstorms EV3 brick beep over a USB connection with Node

play_sound_ev3_usb.js

var LEGO_VENDOR_ID = 0x0694;

var EV3_PRODUCT_ID = 0x0005;

var DIRECT_COMMAND = 0x80;

var usb = require('usb');

var device = usb.findByIds(LEGO_VENDOR_ID, EV3_PRODUCT_ID);

device.open();

var interface = device.interface(0);

if (interface.isKernelDriverActive()) {
    interface.detachKernelDriver();
}

interface.claim();

var buf = new Buffer(17);

buf.fill(0); // For debugging so if we use console.log(buf) we can see what bytes have been written.

// First two bytes is message length (excluding first two bytes) in Little Endian

buf.writeUInt16LE(15);

// Third and fourth bytes are the message counter in Little Endian

buf.writeUInt16LE(1, 2);

// Fifth byte is the command type

buf.writeUInt8(DIRECT_COMMAND, 4);

// Sixth and seventh bytes are local and global vars (which we aren't using here)

buf.writeUInt8(0x00, 5);

buf.writeUInt8(0x00, 6);

// Command follows starting with opSound (0x94)

buf.writeUInt8(0x94, 7);

buf.writeUInt8(0x01, 8);

buf.writeUInt8(0x81, 9);

buf.writeUInt8(0x02, 10);

buf.writeUInt8(0x82, 11);

buf.writeUInt8(0xe8, 12);

buf.writeUInt8(0x03, 13);

buf.writeUInt8(0x82, 14);

buf.writeUInt8(0xe8, 15);

buf.writeUInt8(0x03, 16);

console.log(buf);

var endpoints = interface.endpoints,
    inEndpoint = endpoints[0],
    outEndpoint = endpoints[1];

// inEndpoint is in to PC
inEndpoint.transferType = usb.LIBUSB_TRANSFER_TYPE_BULK;
inEndpoint.startPoll();
inEndpoint.on('data', function (data) {
    console.log(data);
});
inEndpoint.on('error', function (error) {
    console.log(error);
});

// outEndpoint is out to device
outEndpoint.transferType = usb.LIBUSB_TRANSFER_TYPE_BULK;
outEndpoint.transfer(buf, function (err) {
    console.log(err);
});