低功耗蓝牙BLE外围模式(peripheral)-使用BLE作为服务端

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:

*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:

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:

https://github.com/vir56k/bluetoothDemo 找到 bleperipheraldemo 文件夹

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