java - 连续同步读写数据通信

Question

我无法从 ble 设备读取数据到 android 应用程序。如果我进行连续和同时的数据通信，无论哪种方式都会断开连接，尽管蓝牙已连接。

我正在尝试从 ble 设备连续接收 30 字节的数据。我尝试更改 mtu 大小但没有用。如果我开始从应用程序发送 30 个字节的数据，从 ble 设备到应用程序的数据接收将停止。我无法同时进行数据通信。有人可以帮我连续进行同步数据通信吗？我以 300 毫秒的速率向 ble 设备发送 30 个字节的数据，我必须以 1 秒的速率从 ble 设备接收 30 个字节的数据。我一次成功地能够读取或写入。但不是同时。

如果我将 mtu 大小固定为 20，那么我可以同时从 ble 设备读取 20 个字节。但是我必须从 ble 设备读取 30 个字节的数据。

我也想知道，有没有可能在ble上连续同时读写而不丢失数据？

我正在执行 gatt.requestMtu(512)，当时 gatt 连接成功。

 public void onConnectionStateChange(BluetoothGatt gatt, int status, int newState) {
            String intentAction;
            if (newState == BluetoothProfile.STATE_CONNECTED) {
                intentAction = ACTION_GATT_CONNECTED;
                mConnectionState = STATE_CONNECTED;
                broadcastUpdate(intentAction);
                gatt.requestMtu(512);
                Intent i = new Intent("status").putExtra("status",staticConnectionStatus);
                sendBroadcast(i);
            } else if (newState == BluetoothProfile.STATE_DISCONNECTED) {
                intentAction = ACTION_GATT_DISCONNECTED;
                mConnectionState = STATE_DISCONNECTED;
                Intent intent = new Intent("status");
                intent.putExtra("status", staticConnectionStatus);
                sendBroadcast(intent);
                Log.d(TAG, "Disconnected from GATT server.");
                broadcastUpdate(intentAction);
            }
        }

    @Override
    public void onCharacteristicRead(BluetoothGatt gatt,
                                     BluetoothGattCharacteristic characteristic,
                                     int status) {


        if (status == BluetoothGatt.GATT_SUCCESS) {
            Log.d(TAG, "ACTION_DATA_AVAILABLE" + ACTION_DATA_AVAILABLE);
            broadcastUpdate(ACTION_DATA_AVAILABLE, characteristic);

            byte[] charValue = characteristic.getValue();
            byte flag = charValue[0];


        } else if (status == BluetoothGatt.GATT_FAILURE) {
            Log.d(TAG, "failed");
        }

        byte[] charValue = characteristic.getValue();
        byte flag = charValue[0];
    }
    @Override
    public void onCharacteristicChanged(BluetoothGatt gatt, BluetoothGattCharacteristic characteristic) {
        //gatt.requestMtu(185);
        broadcastUpdate(ACTION_DATA_AVAILABLE, characteristic);
        byte[] charValue = characteristic.getValue();
        byte flag = charValue[0];

    }
};



  public void writeRXCharacteristic(byte[] value) {


        if (mBluetoothGatt != null) {


//            try {
//                Thread.sleep(200);
//            } catch (InterruptedException e) {
//                e.printStackTrace();
//            }

            BluetoothGattService RxService = mBluetoothGatt.getService(UUID.fromString("0000FEFB-0000-1000-8000-00805F9B34FB"));

            if (RxService == null) {
//                showMessage("Rx service not found!");
                broadcastUpdate(DEVICE_DOES_NOT_SUPPORT_UART);
                return;
            }
            BluetoothGattCharacteristic RxChar = RxService.getCharacteristic(UUID.fromString("00000001-0000-1000-8000-008025000000"));

            if (RxChar == null) {
//                showMessage("Rx charateristic not found!");
                broadcastUpdate(DEVICE_DOES_NOT_SUPPORT_UART);
                return;
            }

            RxChar.setWriteType(BluetoothGattCharacteristic.WRITE_TYPE_DEFAULT);
            RxChar.setValue(value);

            if (mBluetoothGatt != null) {
                boolean status = mBluetoothGatt.writeCharacteristic(RxChar);
            } else {
                broadcastUpdate(DEVICE_DOES_NOT_SUPPORT_UART);
            }


        } else {
            broadcastUpdate(DEVICE_DOES_NOT_SUPPORT_UART);
        }

    }


//Im notifying the service UUID on services discovered
        BluetoothGattCharacteristic TxChar = RxService.getCharacteristic(UUID.fromString("00000002-0000-1000-8000-008025000000"));
    mBluetoothGatt.setCharacteristicNotification(TxChar, true);

Answer 1

下面是一些可比较的 Kotlin 代码，它们适用于串行连接并增加了 MTU 大小。我删除了错误处理、日志记录和一些特定于应用程序的代码。

它使用了两个特性: - command 特性用于将数据从手机发送到设备。 - feedback 特性用于接收设备发送的数据。

注意它的工作方式:

• 创建工作连接会经历几个阶段，并等待每个阶段完成后再开始下一阶段:连接、发现服务、增加 MTU。
• 特征在服务被发现后保存在实例变量中。
• 修改MTU回调后连接就绪。
• 在更改 MTU 后启用通知。
• 启用通知是用setCharacteristicNotification完成的.无需摆弄描述符。

import android.bluetooth.BluetoothGatt
import android.bluetooth.BluetoothGattCallback
import android.bluetooth.BluetoothGattCharacteristic
import android.bluetooth.BluetoothProfile

class BleConnection(private val device: BluetoothDevice) : Connection {

    private var deviceGatt: BluetoothGatt? = null
    private var commandCharacteristic: BluetoothGattCharacteristic? = null
    private var feedbackCharacteristic: BluetoothGattCharacteristic? = null

    private val gattCallback = object: BluetoothGattCallback() {    
        override fun onConnectionStateChange(gatt: BluetoothGatt?, status: Int, newState: Int) {
            this@BleConnection.onConnectionStateChange(gatt, newState)
        }
        override fun onServicesDiscovered(gatt: BluetoothGatt?, status: Int) {
            this@BleConnection.onServicesDiscovered(gatt)
        }
        override fun onCharacteristicChanged(gatt: BluetoothGatt?, characteristic: BluetoothGattCharacteristic?) {
            this@BleConnection.onCharacteristicChanged(characteristic)
        }
        override fun onMtuChanged(gatt: BluetoothGatt?, mtu: Int, status: Int) {
            this@BleConnection.onMtuChange(gatt)
        }
    }

    // Start to connect
    override fun connect() {
        deviceGatt = device.connectGatt(null, false, gattCallback)
    }

    // The connection state has changed
    private fun onConnectionStateChange(gatt: BluetoothGatt?, newState: Int) {
        when (newState) {
            BluetoothProfile.STATE_CONNECTED -> {
                gatt!!.discoverServices()
            }
            BluetoothProfile.STATE_DISCONNECTED -> {
                ...
            }
        }
    }

    // GATT services have been discovered
    fun onServicesDiscovered(gatt: BluetoothGatt?) {    
        for (service in gatt!!.services) {  
            if (service.uuid == Constants.SERVICE_UUID) {
                feedbackCharacteristic = service.getCharacteristic(Constants.FEEDBACK_CHAR_UUID)
                commandCharacteristic = service.getCharacteristic(Constants.COMMAND_CHAR_UUID)
                 // Increase the MTU
                 gatt.requestMtu(256)
            }
        }
    }

    // The MTU has successfully been changed
    fun onMtuChange(gatt: BluetoothGatt?) {
        gatt!!.setCharacteristicNotification(feedbackCharacteristic, true)
        // ... notify that connection is fully established and ready
    } 

    // Characteristic has been changed (i.e. new data has been received)
    fun onCharacteristicChanged(characteristic: BluetoothGattCharacteristic?) {
        val data = characteristic!!.value
        // ... process the received data
    }

    // may only be called after the connection has been fully established
    // (see onMtuChange() )
    override fun sendData(command: ByteArray) {
        commandCharacteristic!!.value = command
        deviceGatt!!.writeCharacteristic(commandCharacteristic!!)
    }    
}