Support notifications

Author: evanxd

lib/bluetooth_device.js

@@ -1,4 +1,4 @@
-/* global EventEmitter2 */
+/* global Bluetooth, EventEmitter2 */
 'use strict';
 
 (function(exports) {
@@ -9,22 +9,44 @@
 
   BluetoothDevice.prototype = Object.create(EventEmitter2.prototype);
 
-  ['writeCharacteristic', 'notifyCharacteristic'].forEach(function(item) {
-    Object.defineProperty(BluetoothDevice.prototype, item, {
-      set: function(value) {
-        this['_' + item] = value;
-      },
-      get: function() {
-        return this['_' + item];
-      }
-    });
-  });
+  BluetoothDevice.prototype.gatt = null;
+  BluetoothDevice.prototype.writeCharacteristic = null;
+  BluetoothDevice.prototype.notifyCharacteristic = null;
+  BluetoothDevice.prototype._isNotificationsStarted = false;
 
   BluetoothDevice.prototype.send = function(data) {
     data = this._parseHexString(data);
     this.writeCharacteristic.writeValue(data);
   };
 
+  BluetoothDevice.prototype.startNotifications = function() {
+    if (this._isNotificationsStarted) {
+      return;
+    } else {
+      this._isNotificationsStarted = true;
+    }
+    var characteristic = this.notifyCharacteristic;
+    this.gatt.addEventListener('characteristicchanged', (evt) => {
+      this.emit('data', evt.characteristic.value);
+    });
+    characteristic.startNotifications();
+    var descriptor = characteristic.descriptors.find(function(descriptor) {
+      return descriptor.uuid === Bluetooth.CCCD_UUID;
+    });
+    if (descriptor) {
+      var arrayBuffer = new ArrayBuffer(2);
+      var uint8Array = new Uint8Array(arrayBuffer);
+      uint8Array[0] = 0x01;
+      uint8Array[1] = 0x00;
+      descriptor.writeValue(arrayBuffer);
+    }
+  };
+
+  BluetoothDevice.prototype.stopNotifications = function() {
+    this._isNotificationsStarted = false;
+    this.notifyCharacteristic.stopNotifications();
+  };
+
   BluetoothDevice.prototype._parseHexString = function(str) {
     var arrayBuffer = new ArrayBuffer(Math.ceil(str.length / 2));
     var uint8Array = new Uint8Array(arrayBuffer);

lib/bluetooth_helper.js

@@ -14,6 +14,7 @@
 
   // The timeout to connect next device. It's used for workaround.
   BluetoothHelper.CONNECTING_TIMEOUT = 1000;
+  BluetoothHelper.prototype.CCCD_UUID = '00002902-0000-1000-8000-00805f9b34fb';
 
   BluetoothHelper.prototype._scan = null;
   BluetoothHelper.prototype._devices = null,
@@ -87,6 +88,7 @@
     });
     if (devcie) {
       // XXX: Workaround to connect multiple devices correctly.
+      devcie.gatt = gatt;
       setTimeout(() => {
         gatt.connect().then(() => {
           this._discoverServices(devcie, gatt);