Android-BLE-Lock intelligent door Lock client practice

BLE: Full name for Bluetooth Low Energy, also known as Bluetooth 4.0, is mainly promoted by Low power consumption. Therefore, BLE technology is more applicable to wearable devices and smart homes. For this reason, our team members choose BLE chips and technologies for development.

• Generic Attribute Profile(GATT) – THE GATT Profile is a Generic specification for sending and receiving data blocks over a BLE link. BLE application development is also based on GATT.
• Attribute Protocol (ATT) – GATT is based on the ATT Protocol and is also called GATT/ATT. ATT is optimized to run on BLE devices, and to do so, it uses as few bytes as possible. Each attribute is identified by a unique unified identifier (UUID), and each String UUID uses the 128-bit standard format. Attributes are formatted as Characteristics and services through ATT.
• A Characteristic variable consists of a single variable and 0-n descriptors used to describe Characteristic variables. Characteristic can be thought of as a type, similar to classes.
• Service Services are a collection of characteristic.

Service, Characteristic, and Descriptor are all unique identifiers (UUID). A Bluetooth 4.0 terminal can contain multiple services, a Service can contain multiple Characteristic, a Characteristic can contain a Value and multiple descriptors, One Descriptor contains a Value. Generally speaking, Characteristic is the key to exchange data between mobile phones and BLE terminals. Characteristic has many fields related to permissions, such as PERMISSION and PROPERTY. Characteristic of the PROPERTY attribute can be set by an operator, speaking, reading and writing, such as READ | WRITE, READ | WRITE_NO_RESPONSE | NOTIFY, so after reading the PROPERTY used to break down into a combination of).

Of course, you should check whether the device supports BLE before setting it. Now mainstream models have perfect BLE support. After checking, you can directly start Bluetooth:

1. It is important to note that in Android there is only one BluetoothAdapter that the APP uses to interact with the system. Here we use getSystemSrvice() to return to BluetoothManager.

   BluetoothManager = (BluetoothManager) getSystemService(context.bluetooth_service); mBluetoothAdapter = bluetoothManager.getAdapter(); Log.i(TAG, "mBluetoothAdapter = " + mBluetoothAdapter);Copy the code

2. Open the bluetooth

   Mbluetoothadapter.enable (); Mactionbar. setSubtitle(" Bluetooth enabled "); myBleAddress = mBluetoothAdapter.getAddress();Copy the code

3. Search equipment

   mBluetoothAdapter.startLeScan(mLeScanCallback);Copy the code

4. Processing search results

   / / equipment search results private BluetoothAdapter. LeScanCallback mLeScanCallback = new BluetoothAdapter. LeScanCallback () {@ Override public void onLeScan(final BluetoothDevice device, int rssi, byte[] scanRecord) { runOnUiThread(new Runnable() { @Override public void run() { //5F:52:CC:7F:86:55 // 20:91:48:50:5E :8E //D4: F5:13:78:e9:63 //20:91:48:50:58:DE Here is the test CC2541 Bluetooth MAC address if (device.getAddress().equals("20:91:48:50:58:DE")) { scanLeDevice(false); Log.e(TAG, device.getAddress()); Log.e(TAG, device.getName()); boolean bRet = mBLE.connect(device.getAddress()); Thread.sleep(2000); thread.sleep (2000); } catch (InterruptedException e) { e.printStackTrace(); } if (bRet) {mactionbar.setSubtitle (" Connected, please log in "); Log.e(TAG, "connect+++++success"); Log.e(TAG, Constant.HEAD_CHAR + "0B" + Constant.SEND_ADDRESS + Constant.SEVER_BLUETOOTH + myBleAddress + Constant.END_CHAR); }}}}); // rssi Log.i(TAG, "rssi = " + rssi); Log.i(TAG, "mac = " + device.getAddress()); Log.i(TAG, "scanRecord.length = " + scanRecord.length); }};Copy the code

5. Communicate in real time

   Write data via writeCharacteristic:

   public static void writeChar(byte[] bytes) {
       Log.i(TAG, "Message = " + bytes);
       if (gattCharacteristic_char != null) {
           gattCharacteristic_char.setValue(bytes);
           mBLE.writeCharacteristic(gattCharacteristic_char);
       }
   }Copy the code

   OnCharacteristicWrite method to read data from bluetooth method:

   private BluetoothLeClass.OnDataAvailableListener mOnDataAvailable = new BluetoothLeClass.OnDataAvailableListener() { /** Override public void onCharacteristicRead(BluetoothGatt, BluetoothGatt, BluetoothGattCharacteristic characteristic, int status) { Log.e(TAG, "onCharRead " + gatt.getDevice().getName() + " read " + characteristic.getUuid().toString() + " -> " + Utils.bytesToHexString(characteristic.getValue())); } @override public void onCharacteristicWrite(BluetoothGatt, BluetoothGatt, BluetoothGattCharacteristic characteristic) { // Log.e(TAG, "onCharWrite " + gatt.getDevice().getName() + " write " // + characteristic.getUuid().toString() + " -> " // + new String(characteristic.getValue())); String str = Utils.bytesToHexString(characteristic.getValue()); Log.e(TAG, "+++++++++++++++++++++" + str); // The data sent by bluetooth is processed here... }};Copy the code

   ​

First of all, in client development, it is not necessary to set baud rate in the program, because it is not serial port development. BLE is highly integrated in Android and only needs to meet the above conditions to communicate, while BLE device development needs to be set, which can be designed according to their own needs. At the same time, when developing and debugging the client, Portland must be set in the serial port assistant. Of course, this value comes from our hardware development students.

In the development of interaction with hardware, we cannot carry out data communication through JOSN or XML and other similar data as in the development of applications. Instead, we should adopt the communication protocol based on the hexadecimal hardware base. Protocol screenshots (pictures cannot be loaded, please refer to here) :

So we do hexadecimal conversions between passed and parsed data:

Public static String toHexString(String s) {String STR = ""; for (int i = 0; i < s.length(); i++) { int ch = (int) s.charAt(i); String s4 = Integer.toHexString(ch); str = str + s4; } return str; } public static String hexToString(String s) {byte[] baKeyword = new byte[s.length() / 2]; for (int i = 0; i < baKeyword.length; i++) { try { baKeyword[i] = (byte) (0xff & Integer.parseInt(s.substring( i * 2, i * 2 + 2), 16)); } catch (Exception e) { e.printStackTrace(); } } try { s = new String(baKeyword, "utf-8"); // UTF-16le:Not } catch (Exception e1) { e1.printStackTrace(); } return s; }Copy the code