usbscanner.js

var HID = require("node-hid");
const EventEmitter = require("events");
var util = require("util");

/*
options:
{vendorId:Int, hidMap: Obj}
defaults:
{vendorId:1534, hidMap:{30: '1', 31: '2', 32: '3', 33: '4',34: '5',35: '6', 36: '7', 37: '8', 38: '9',39: '0',40: 'e'}}
*/
function usbScanner(options) {
  var opts = options || {};
  this.init(opts);
  EventEmitter.call(this);
}

//enherit event emitter
util.inherits(usbScanner, EventEmitter);

function getDevices() {
  return HID.devices();
}

usbScanner.prototype.init = function(options) {
  var vendorId = options.vendorId || 1534;
  var devicePath = options.devicePath || null;

  //hidMap defining keyboard code to coresponding string value
  this.hidMap = options.hidMap || {
    4: "A",
    5: "B",
    6: "C",
    7: "D",
    8: "E",
    9: "F",
    10: "G",
    11: "H",
    12: "I",
    13: "J",
    14: "K",
    15: "L",
    16: "M",
    17: "N",
    18: "O",
    19: "P",
    20: "Q",
    21: "R",
    22: "S",
    23: "T",
    24: "U",
    25: "V",
    26: "W",
    27: "X",
    28: "Y",
    29: "Z",
    30: "1",
    31: "2",
    32: "3",
    33: "4",
    34: "5",
    35: "6",
    36: "7",
    37: "8",
    38: "9",
    // enter - barcode escape char
    39: "0",
    40: "enter",
    44: " ",
    45: "-",
    55: ".",
    56: "/",
    85: "*",
    87: "+"
  };

  var scanner = devicePath
    ? { path: devicePath }
    : getDevices().find(device => device.vendorId === vendorId);

  this.device = new HID.HID(scanner.path);
  // start waiting for scan events
  this.startScanning();
};

usbScanner.prototype.startScanning = function() {
  //empty array for barcode bytes
  var bcodeBuff = [];
  //string variable to hold barcode string
  var aBarcode = "";
  //event emitter for when newCode is read from scanner

  this.device.on("data", chunk => {
    //second byte of buffer is all that contains data
    if (this.hidMap[chunk[2]]) {
      //if not bcodeBuff escape char (40)
      if (chunk[2] !== 40) {
        bcodeBuff.push(this.hidMap[chunk[2]]);
      } else {
        //revieved escape code, join bCodebuff array and
        aBarcode = bcodeBuff.join("");
        bcodeBuff = [];
        //emit newCode event
        this.emit("data", aBarcode);
      }
    }
  });
};

usbScanner.prototype.stopScanning = function() {
  this.device.close();
};

module.exports = { usbScanner: usbScanner, getDevices: getDevices };