Low Power Bluetooth BLE Peripheral mode - Use BLE as the server

#低功耗蓝牙BLE外围模式(peripheral)-使用BLE作为服务端

## Android对外模模式(peripheral)的支持

从Android5.0开始才支持

##关键术语和概念

以下是关键BLE术语和概念的摘要：

* 通用属性简档（GATT） – GATT简档是用于通过BLE链路发送和接收称为“属性”的短数据块的一般规范。所有当前的低能量应用配置文件都基于GATT。

蓝牙SIG为低能量设备定义了许多配置文件。配置文件是设备在特定应用程序中的工作方式的规范。请注意，设备可以实现多个配置文件。例如，设备可以包含心率监视器和电池水平检测器。

* 属性协议（ATT） -GATT建立在属性协议（ATT）之上。这也称为GATT / ATT。 ATT经过优化，可在BLE设备上运行。为此，它使用尽可能少的字节。每个属性由通用唯一标识符（UUID）唯一标识，UUID是用于唯一标识信息的字符串ID的标准化128位格式。由ATT传送的属性被格式化为特征和服务。

* 特性 -A特性包含描述特性值的单个值和0-n个描述符。一个特性可以被认为是一个类型，类似于类。

* 描述符 – 描述符是描述特征值的定义属性。例如，描述符可以指定人类可读的描述，特征值的可接受范围或特征值的特定的测量单位。

* 服务 – 服务是一个集合的特点。例如，您可以有一个名为“心率监视器”的服务，其中包括诸如“心率测量”的特征。您可以在bluetooth.org上找到现有基于GATT的个人资料和服务的列表。

##角色和职责

以下是Android设备与BLE设备互动时适用的角色和职责：

##中央与外围。这适用于BLE连接本身。处于中心角色的设备扫描，寻找广告，并且外围角色中的设备进行广告。

GATT服务器与GATT客户端。这决定了两个设备在建立连接后如何相互通信。

#BLE权限

首先，需要在manifest中声明使用蓝牙和操作蓝牙的权限

在应用程序清单文件中声明蓝牙权限。例如：

<uses-permission android:name=”android.permission.BLUETOOTH”/>

<uses-permission android:name=”android.permission.BLUETOOTH_ADMIN”/>

如果您要声明自己的应用只适用于支持BLE的设备，请在应用清单中包含以下内容：

<uses-feature android：name =“android.hardware.bluetooth_le”android：required =“true”/>

不过，如果您想让应用程式适用于不支援BLE的装置，您仍应在应用的清单中加入这个元素，但required=”false”设为required=”false” 。

然后在运行时，您可以通过使用PackageManager.hasSystemFeature()确定BLE可用性：

// Use this check to determine whether BLE is supported on the device. Then

// you can selectively disable BLE-related features.

if (!getPackageManager().hasSystemFeature(PackageManager.FEATURE_BLUETOOTH_LE)) {

Toast.makeText(this, R.string.ble_not_supported, Toast.LENGTH_SHORT).show();

finish();

}

在android 6.0 以后，要想获得蓝牙扫描结果，还需要下面的权限

<manifest … >

<uses-permission android:name=”android.permission.ACCESS_FINE_LOCATION” />

…

<!– Needed only if your app targets Android 5.0 (API level 21) or higher. –>

<uses-feature android:name=”android.hardware.location.gps” />

…

</manifest>

#设置蓝牙

## 1.Get the BluetoothAdapter

获得蓝牙适配器

private BluetoothAdapter mBluetoothAdapter;

…

// Initializes Bluetooth adapter.

final BluetoothManager bluetoothManager =

(BluetoothManager) getSystemService(Context.BLUETOOTH_SERVICE);

mBluetoothAdapter = bluetoothManager.getAdapter();

## 2.Enable Bluetooth

打开蓝牙

// Ensures Bluetooth is available on the device and it is enabled. If not,

// displays a dialog requesting user permission to enable Bluetooth.

if (mBluetoothAdapter == null || !mBluetoothAdapter.isEnabled()) {

Intent enableBtIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);

startActivityForResult(enableBtIntent, REQUEST_ENABLE_BT);

}

# 3.初始化BLE蓝牙广播（广告）

(1)广播的设置

(2)设置广播的数据

(3)设置响应的数据

(4)设置连接回调

private void initGATTServer() {

AdvertiseSettings settings = new AdvertiseSettings.Builder()

.setConnectable(true)

.build();

AdvertiseData advertiseData = new AdvertiseData.Builder()

.setIncludeDeviceName(true)

.setIncludeTxPowerLevel(true)

.build();

AdvertiseData scanResponseData = new AdvertiseData.Builder()

.addServiceUuid(new ParcelUuid(UUID_SERVER))

.setIncludeTxPowerLevel(true)

.build();

AdvertiseCallback callback = new AdvertiseCallback() {

@Override

public void onStartSuccess(AdvertiseSettings settingsInEffect) {

Log.d(TAG, “BLE advertisement added successfully”);

showText(“1. initGATTServer success”);

println(“1. initGATTServer success”);

initServices(getContext());

}

@Override

public void onStartFailure(int errorCode) {

Log.e(TAG, “Failed to add BLE advertisement, reason: ” + errorCode);

showText(“1. initGATTServer failure”);

}

};

BluetoothLeAdvertiser bluetoothLeAdvertiser = mBluetoothAdapter.getBluetoothLeAdvertiser();

bluetoothLeAdvertiser.startAdvertising(settings, advertiseData, scanResponseData, callback);

}

在被BLE设备连接后，将触发 AdvertiseCallback 的 onStartSuccess，我们在这之后，初始化GATT的服务

# 4.初始化GATT的服务

(1) 通过 mBluetoothManager.openGattServer() 获得 bluetoothGattServer

(2) 添加服务，特征，描述。这些内容要让客户端知道。

private void initServices(Context context) {

bluetoothGattServer = mBluetoothManager.openGattServer(context, bluetoothGattServerCallback);

BluetoothGattService service = new BluetoothGattService(UUID_SERVER, BluetoothGattService.SERVICE_TYPE_PRIMARY);

//add a read characteristic.

characteristicRead = new BluetoothGattCharacteristic(UUID_CHARREAD, BluetoothGattCharacteristic.PROPERTY_READ, BluetoothGattCharacteristic.PERMISSION_READ);

//add a descriptor

BluetoothGattDescriptor descriptor = new BluetoothGattDescriptor(UUID_DESCRIPTOR, BluetoothGattCharacteristic.PERMISSION_WRITE);

characteristicRead.addDescriptor(descriptor);

service.addCharacteristic(characteristicRead);

//add a write characteristic.

BluetoothGattCharacteristic characteristicWrite = new BluetoothGattCharacteristic(UUID_CHARWRITE,

BluetoothGattCharacteristic.PROPERTY_WRITE |

BluetoothGattCharacteristic.PROPERTY_READ |

BluetoothGattCharacteristic.PROPERTY_NOTIFY,

BluetoothGattCharacteristic.PERMISSION_WRITE);

service.addCharacteristic(characteristicWrite);

bluetoothGattServer.addService(service);

Log.e(TAG, “2. initServices ok”);

showText(“2. initServices ok”);

}

在 openGattServer 方法中，我们需要传入个回调

bluetoothGattServer = mBluetoothManager.openGattServer(context, bluetoothGattServerCallback);

## 5.配置数据交互回调

回调时间有：连接状态变化，收发消息，通知消息

/**

* 服务事件的回调

*/

private BluetoothGattServerCallback bluetoothGattServerCallback = new BluetoothGattServerCallback() {

/**

* 1.连接状态发生变化时

* @param device

* @param status

* @param newState

*/

@Override

public void onConnectionStateChange(BluetoothDevice device, int status, int newState) {

Log.e(TAG, String.format(“1.onConnectionStateChange：device name = %s, address = %s”, device.getName(), device.getAddress()));

Log.e(TAG, String.format(“1.onConnectionStateChange：status = %s, newState =%s “, status, newState));

super.onConnectionStateChange(device, status, newState);

}

@Override

public void onServiceAdded(int status, BluetoothGattService service) {

super.onServiceAdded(status, service);

Log.e(TAG, String.format(“onServiceAdded：status = %s”, status));

}

@Override

public void onCharacteristicReadRequest(BluetoothDevice device, int requestId, int offset, BluetoothGattCharacteristic characteristic) {

Log.e(TAG, String.format(“onCharacteristicReadRequest：device name = %s, address = %s”, device.getName(), device.getAddress()));

Log.e(TAG, String.format(“onCharacteristicReadRequest：requestId = %s, offset = %s”, requestId, offset));

bluetoothGattServer.sendResponse(device, requestId, BluetoothGatt.GATT_SUCCESS, offset, characteristic.getValue());

// super.onCharacteristicReadRequest(device, requestId, offset, characteristic);

}

/**

* 3. onCharacteristicWriteRequest,接收具体的字节

* @param device

* @param requestId

* @param characteristic

* @param preparedWrite

* @param responseNeeded

* @param offset

* @param requestBytes

*/

@Override

public void onCharacteristicWriteRequest(BluetoothDevice device, int requestId, BluetoothGattCharacteristic characteristic, boolean preparedWrite, boolean responseNeeded, int offset, byte[] requestBytes) {

Log.e(TAG, String.format(“3.onCharacteristicWriteRequest：device name = %s, address = %s”, device.getName(), device.getAddress()));

Log.e(TAG, String.format(“3.onCharacteristicWriteRequest：requestId = %s, preparedWrite=%s, responseNeeded=%s, offset=%s, value=%s”, requestId, preparedWrite, responseNeeded, offset, OutputStringUtil.toHexString(requestBytes)));

bluetoothGattServer.sendResponse(device, requestId, BluetoothGatt.GATT_SUCCESS, offset, requestBytes);

//4.处理响应内容

onResponseToClient(requestBytes, device, requestId, characteristic);

}

/**

* 2.描述被写入时，在这里执行 bluetoothGattServer.sendResponse(device, requestId, BluetoothGatt.GATT_SUCCESS… 收，触发 onCharacteristicWriteRequest

* @param device

* @param requestId

* @param descriptor

* @param preparedWrite

* @param responseNeeded

* @param offset

* @param value

*/

@Override

public void onDescriptorWriteRequest(BluetoothDevice device, int requestId, BluetoothGattDescriptor descriptor, boolean preparedWrite, boolean responseNeeded, int offset, byte[] value) {

Log.e(TAG, String.format(“2.onDescriptorWriteRequest：device name = %s, address = %s”, device.getName(), device.getAddress()));

Log.e(TAG, String.format(“2.onDescriptorWriteRequest：requestId = %s, preparedWrite = %s, responseNeeded = %s, offset = %s, value = %s,”, requestId, preparedWrite, responseNeeded, offset, OutputStringUtil.toHexString(value)));

// now tell the connected device that this was all successfull

bluetoothGattServer.sendResponse(device, requestId, BluetoothGatt.GATT_SUCCESS, offset, value);

}

/**

* 5.特征被读取。当回复响应成功后，客户端会读取然后触发本方法

* @param device

* @param requestId

* @param offset

* @param descriptor

*/

@Override

public void onDescriptorReadRequest(BluetoothDevice device, int requestId, int offset, BluetoothGattDescriptor descriptor) {

Log.e(TAG, String.format(“onDescriptorReadRequest：device name = %s, address = %s”, device.getName(), device.getAddress()));

Log.e(TAG, String.format(“onDescriptorReadRequest：requestId = %s”, requestId));

// super.onDescriptorReadRequest(device, requestId, offset, descriptor);

bluetoothGattServer.sendResponse(device, requestId, BluetoothGatt.GATT_SUCCESS, offset, null);

}

@Override

public void onNotificationSent(BluetoothDevice device, int status) {

super.onNotificationSent(device, status);

Log.e(TAG, String.format(“5.onNotificationSent：device name = %s, address = %s”, device.getName(), device.getAddress()));

Log.e(TAG, String.format(“5.onNotificationSent：status = %s”, status));

}

@Override

public void onMtuChanged(BluetoothDevice device, int mtu) {

super.onMtuChanged(device, mtu);

Log.e(TAG, String.format(“onMtuChanged：mtu = %s”, mtu));

}

@Override

public void onExecuteWrite(BluetoothDevice device, int requestId, boolean execute) {

super.onExecuteWrite(device, requestId, execute);

Log.e(TAG, String.format(“onExecuteWrite：requestId = %s”, requestId));

}

};

## 6.处理来自客户端发来的数据和发送回复数据：

调用 bluetoothGattServer.notifyCharacteristicChanged 方法，通知数据改变。

/**

* 4.处理响应内容

*

* @param reqeustBytes

* @param device

* @param requestId

* @param characteristic

*/

private void onResponseToClient(byte[] reqeustBytes, BluetoothDevice device, int requestId, BluetoothGattCharacteristic characteristic) {

Log.e(TAG, String.format(“4.onResponseToClient：device name = %s, address = %s”, device.getName(), device.getAddress()));

Log.e(TAG, String.format(“4.onResponseToClient：requestId = %s”, requestId));

String msg = OutputStringUtil.transferForPrint(reqeustBytes);

println(“4.收到:” + msg);

showText(“4.收到:” + msg);

String str = new String(reqeustBytes) + ” hello>”;

characteristicRead.setValue(str.getBytes());

bluetoothGattServer.notifyCharacteristicChanged(device, characteristicRead, false);

println(“4.响应:” + str);

showText(“4.响应:” + str);

}

### 交互流程：

(1) 当客户端开始写入数据时：触发回调方法 onDescriptorWriteRequest

(2) 在 onDescriptorWriteRequest 方法中，执行下面的方法表示写入成功 BluetoothGatt.GATT_SUCCESS

bluetoothGattServer.sendResponse(device, requestId, BluetoothGatt.GATT_SUCCESS, offset, value);

执行 sendResponse后，会触发回调方法 onCharacteristicWriteRequest

(3) 在 onCharacteristicWriteRequest方法中

public void onCharacteristicWriteRequest(BluetoothDevice device, int requestId, BluetoothGattCharacteristic characteristic, boolean preparedWrite, boolean responseNeeded, int offset, byte[] requestBytes) {

这个里可以获得来自客户端发来的数据 requestBytes

(4) 处理响应内容,我写了这个方法：

onResponseToClient(requestBytes, device, requestId, characteristic);

在这个方法中，通过 bluetoothGattServer.notifyCharacteristicChanged()方法回复数据

###通过日志，我们看看事件触发的顺序

1.onConnectionStateChange：device name = null, address = 74:32:DE:49:3C:28

1.onConnectionStateChange：status = 0, newState =2

2.onDescriptorWriteRequest：device name = null, address = 74:32:DE:49:3C:28

2.onDescriptorWriteRequest：requestId = 1, preparedWrite = false, responseNeeded = true, offset = 0, value = [01,00,],

3.onCharacteristicWriteRequest：device name = null, address = 74:32:DE:49:3C:28

3.onCharacteristicWriteRequest：requestId = 2, preparedWrite=false, responseNeeded=false, offset=0, value=[41,54,45,30,0D,]

4.onResponseToClient：device name = null, address = 74:32:DE:49:3C:28

4.onResponseToClient：requestId = 2

4.收到:ATE0

4.响应:ATE0 hello>

5.onNotificationSent：device name = null, address = 74:32:DE:49:3C:28

5.onNotificationSent：status = 0

代码托管到github:

github.com/vir56k/blue… 找到 bleperipheraldemo 文件夹

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Low Power Bluetooth BLE Peripheral mode – Use BLE as the server

Low Power Bluetooth BLE Peripheral mode – Use BLE as the server

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