Interfacing to Adafruit fingerprint sensor

Hi,
I finally managed to make the fingerprint sensor working,
with print recognition and code for enrollment.
Here is the code :

var C = {
  FINGERPRINT_OK                 : 0x00,
  FINGERPRINT_PACKETRECIEVEERR   : 0x01,
  FINGERPRINT_NOFINGER           : 0x02,
  FINGERPRINT_IMAGEFAIL          : 0x03,
  FINGERPRINT_IMAGEMESS          : 0x06,
  FINGERPRINT_FEATUREFAIL        : 0x07,
  FINGERPRINT_NOMATCH            : 0x08,
  FINGERPRINT_NOTFOUND           : 0x09,
  FINGERPRINT_ENROLLMISMATCH     : 0x0A,
  FINGERPRINT_BADLOCATION        : 0x0B,
  FINGERPRINT_DBRANGEFAIL        : 0x0C,
  FINGERPRINT_UPLOADFEATUREFAIL  : 0x0D,
  FINGERPRINT_PACKETRESPONSEFAIL : 0x0E,
  FINGERPRINT_UPLOADFAIL         : 0x0F,
  FINGERPRINT_DELETEFAIL         : 0x10,
  FINGERPRINT_DBCLEARFAIL        : 0x11,
  FINGERPRINT_PASSFAIL           : 0x13,
  FINGERPRINT_INVALIDIMAGE       : 0x15,
  FINGERPRINT_FLASHERR           : 0x18,
  FINGERPRINT_INVALIDREG         : 0x1A,
  FINGERPRINT_ADDRCODE           : 0x20,
  FINGERPRINT_PASSVERIFY         : 0x21,
  //
  FINGERPRINT_STARTCODE          : 0xEF01,
  //
  FINGERPRINT_COMMANDPACKET      : 0x1,
  FINGERPRINT_DATAPACKET         : 0x2,
  FINGERPRINT_ACKPACKET          : 0x7,
  FINGERPRINT_ENDDATAPACKET      : 0x8,
  //
  FINGERPRINT_TIMEOUT            : 0xFF,
  FINGERPRINT_BADPACKET          : 0xFE,
  //
  FINGERPRINT_GETIMAGE           : 0x01,
  FINGERPRINT_IMAGE2TZ           : 0x02,
  FINGERPRINT_REGMODEL           : 0x05,
  FINGERPRINT_STORE              : 0x06,
  FINGERPRINT_EMPTY              : 0x0D,
  FINGERPRINT_VERIFYPASSWORD     : 0x13,
  FINGERPRINT_HISPEEDSEARCH      : 0x1B,
  FINGERPRINT_TEMPLATECOUNT      : 0x1D,
  //
  DEFAULTTIMEOUT : 5000 // milliseconds
};

var serialTTL = null;
var thePassword = 0;
var theAddress = 0xFFFFFFFF;

function connect(serial) {
  serialTTL = serial;
  serialTTL.setup(57600);
}

function checkSensor(callback) {
  var packet = [
    C.FINGERPRINT_VERIFYPASSWORD,
    (thePassword >> 24) & 0xFF,
    (thePassword >> 16) & 0xFF,
    (thePassword >> 8) & 0xFF,
    thePassword & 0xFF
  ];
  sendPacket(packet, callback);
}

function getImage(callback) {
  sendPacket([C.FINGERPRINT_GETIMAGE], callback);
}

function image2Tz(slot, callback) {
  sendPacket([C.FINGERPRINT_IMAGE2TZ, (slot & 0xFF)], callback);
}

function createModel(callback) {
  sendPacket([C.FINGERPRINT_REGMODEL], callback);
}

function storeModel(id, callback) {
  sendPacket([C.FINGERPRINT_STORE, 0x01, (id >> 8) & 0xFF, id & 0xFF], callback);
}

function emptyDatabase(callback) {
  sendPacket([C.FINGERPRINT_EMPTY], callback);
}

function fingerFastSearch(callback) {
  var fingerID = 0xFFFF;
  var confidence = 0xFFFF;
  var packet = [C.FINGERPRINT_HISPEEDSEARCH, 0x01 & 0xFF, 0x00  & 0xFF, 0x00 & 0xFF, 0x00 & 0xFF, 0xA3 & 0xFF];
  writePacket(theAddress, C.FINGERPRINT_COMMANDPACKET, packet);
  getReply(packet, function(len, packet) {
    if ((len != 1) && (packet[0] != C.FINGERPRINT_ACKPACKET)) {
      callback(-1, null);
      return;
    }
    fingerID = packet[2];
    fingerID <<= 8;
    fingerID |= packet[3];
    confidence = packet[4];
    confidence <<= 8;
    confidence |= packet[5];
    callback(null, {'responseCode': packet[1], 'fingerID': fingerID, 'confidence': confidence});
  });
}

function getTemplateCount(callback) {
  var templateCount = 0xFFFF;
  var packet = [C.FINGERPRINT_TEMPLATECOUNT];
  writePacket(theAddress, C.FINGERPRINT_COMMANDPACKET, packet);
  getReply(packet, function(len, packet) {
    if ((len != 1) && (packet[0] != C.FINGERPRINT_ACKPACKET)) {
      callback(-1, null);
      return;
    }
    templateCount = packet[2];
    templateCount <<= 8;
    templateCount |= packet[3];
    callback(null, {'responseCode': packet[1], 'templateCount': templateCount});
  });
}

function writePacket(addr, packetType, packet) {
  var len = packet.length+2;
  serialTTL.write([
    (C.FINGERPRINT_STARTCODE >> 8) & 0xFF,
    C.FINGERPRINT_STARTCODE & 0xFF,
    (addr >> 24) & 0xFF,
    (addr >> 16) & 0xFF,
    (addr >> 8) & 0xFF,
    addr & 0xFF,
    packetType,
    (len >> 8) & 0xFF,
    len &0xFF
  ]);
  var sum = (len>>8) + (len&0xFF) + packetType;
  serialTTL.write(packet);
  for (var i in packet) sum += packet[i];
  serialTTL.write([(sum>>8)&0xFF, sum&0xFF]);
}

function getReply(packet, callback) {
  var receivedData = [];

  serialTTL.onData(function (e) {
    receivedData.push(e.data.charCodeAt(0));

    if ( (idx === 0) && (receivedData[0] != ( (C.FINGERPRINT_STARTCODE >> 8) & 0xFF) ))
      return;

    if (receivedData.length >= 9) {
      if (( receivedData[0] != (C.FINGERPRINT_STARTCODE >> 8)) ||
          ( receivedData[1] != (C.FINGERPRINT_STARTCODE & 0xFF))) {
        callback(-1, {'responseCode': C.FINGERPRINT_BADPACKET});
        return;
      }

      var packettype = receivedData[6];
      var len = receivedData[7];

      len <<= 8;
      len |= receivedData[8];
      len -= 2;

      if (receivedData.length <= (len+10))
        return;

      packet[0] = packettype;

      for (var i=0; i<len; i++) {
        packet[1+i] = receivedData[9+i];
      }

      callback(len, packet);
    }
  });
}

function sendPacket(packet, callback) {
  writePacket(theAddress, C.FINGERPRINT_COMMANDPACKET, packet);
  getReply(packet, function(len, packet) {
    if ((len != 1) && (packet[0] != C.FINGERPRINT_ACKPACKET))
      callback(-1, null);
    else
      callback(len, {'responseCode': packet[1]});
  });
}

function getErrorCode(responseCode) {
  var res = null;
  switch (responseCode & 0xFF) {
    case C.FINGERPRINT_OK:
      res = null;
      break;
    case C.FINGERPRINT_NOFINGER:
      res = "No Finger";
      break;
    case C.FINGERPRINT_PACKETRECIEVEERR:
      res = "Communication error";
      break;
    case C.FINGERPRINT_IMAGEFAIL:
      res = "Imaging error";
      break;
    case C.FINGERPRINT_IMAGEMESS:
      res = "Image too messy";
      break;
    case C.FINGERPRINT_FEATUREFAIL:
      res = "Could not find fingerprint features";
      break;
    case C.FINGERPRINT_INVALIDIMAGE:
      res = "Could not find fingerprint features";
      break;
    case C.FINGERPRINT_ENROLLMISMATCH:
      res = "Prints did not match";
      break;
    case C.FINGERPRINT_BADLOCATION:
      res = "Could not store in that location";
      break;
    case C.FINGERPRINT_BADPACKET:
      res = "Communication error";
      break;
    case C.FINGERPRINT_FLASHERR:
      res = "Error writing to flash";
      break;
    default:
      res = "Unknown error";
  }
  return res;
}