Android Java

Android：通过BLE发送大于20个字节的数据

发布于 2021-02-02 22:42:38

通过连接到外部BLE设备，我最多可以发送20个字节的数据。如何发送大于20个字节的数据。我已经读到我们必须将数据分段或将特征拆分为所需的部分。如果我假设我的数据是32字节，你能否告诉我我需要在代码中进行的更改才能使其正常工作？以下是我的代码中必需的摘录：

public boolean send(byte[] data) {
    if (mBluetoothGatt == null || mBluetoothGattService == null) {
        Log.w(TAG, "BluetoothGatt not initialized");
        return false;
    }

    BluetoothGattCharacteristic characteristic =
            mBluetoothGattService.getCharacteristic(UUID_SEND);

    if (characteristic == null) {
        Log.w(TAG, "Send characteristic not found");
        return false;
    }

    characteristic.setValue(data);
    characteristic.setWriteType(BluetoothGattCharacteristic.WRITE_TYPE_NO_RESPONSE);
    return mBluetoothGatt.writeCharacteristic(characteristic);
}

这是我用于发送数据的代码。在以下onclick事件中使用“发送”功能。

sendValueButton = (Button) findViewById(R.id.sendValue);
    sendValueButton.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            String text = dataEdit.getText().toString();                           
            yableeService.send(text.getBytes());
        }
    });

当String text大于20个字节时，则仅接收前20个字节。如何纠正呢？

为了测试发送多个特征，我尝试了以下操作：

sendValueButton = (Button) findViewById(R.id.sendValue);
sendValueButton.setOnClickListener(new View.OnClickListener() {
    @Override
    public void onClick(View v) {
        String text = "Test1";                           
        yableeService.send(text.getBytes());

        text = "Test2";                           
        yableeService.send(text.getBytes());

        text = "Test3";                           
        yableeService.send(text.getBytes());
    }
});

但是我只收到“ Test3”，即最后一个特征。我犯了什么错误？我是BLE新手，所以请忽略任何幼稚

编辑：

在为以后查看此内容的任何人接受答案之后。

有两种方法可以完成此操作。1.拆分数据并像所选答案一样循环编写。2.拆分数据并使用回调（即）进行写入onCharacterisitcWrite()。如果在编写过程中出现任何错误，这将使你免于错误。

但是，如果你只是在写而不等待固件的响应，则两次写之间最重要的是使用a Thread.sleep(200)。这将确保你的所有数据都能到达。没有sleepI，我总是得到最后一个数据包。如果你注意到已接受的答案，他也会sleep在两者之间使用。

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1 个回答

面试哥 2021-02-02

为面试而生，有面试问题，就找面试哥。

BLE最多允许你传输20个字节。

如果要发送20个以上的字节，则应定义数组byte[]以包含所需的数据包数量。

如果你要发送少于160个字符（160个字节），以下示例可以很好地工作。

p / s：根据需要编辑以下内容。不要完全跟随我。

实际上，当我们使用BLE时，移动端和固件端需要设置密钥（例如0x03...）来定义双方之间的连接门。

这个想法是：

当我们继续传输数据包时，不是最后一个。门是byte[1] = 0x01。
如果我们发送最后一个，则门为byte[1] = 0x00。

数据构造（20字节）：

1– Byte 1定义Gate ID：例如。消息门ID byte[0] = 0x03。

2- Byte 2定义recognization：是最后一个数据包0x00还是继续发送数据包0x01。

3- Byte 3（在消除Byte 1＆之后，应为18个字节Byte 2）-在此处附加消息内容。

在阅读下面的代码之前，请先了解我的逻辑。

下面是发送带有许多数据包的消息的示例，每个数据包是一个大小为20字节的数组。

private void sendMessage(BluetoothGattCharacteristic characteristic, String CHARACTERS){
        byte[] initial_packet = new byte[3];
        /**
         * Indicate byte
         */
        initial_packet[0] = BLE.INITIAL_MESSAGE_PACKET;
        if (Long.valueOf(
                String.valueOf(CHARACTERS.length() + initial_packet.length))
                > BLE.DEFAULT_BYTES_VIA_BLE) {
            sendingContinuePacket(characteristic, initial_packet, CHARACTERS);
        } else {
            sendingLastPacket(characteristic, initial_packet, CHARACTERS);
        }
    }

private void sendingContinuePacket(BluetoothGattCharacteristic characteristic,
            byte[] initial_packet, String CHARACTERS){
        /**
         * TODO If data length > Default data can sent via BLE : 20 bytes
         */
        // Check the data length is large how many times with Default Data (BLE)
        int times = Byte.valueOf(String.valueOf(
                CHARACTERS.length() / BLE.DEFAULT_BYTES_IN_CONTINUE_PACKET));

        Log.i(TAG, "CHARACTERS.length() " + CHARACTERS.length());
        Log.i(TAG, "times " + times);

        // TODO
        // 100 : Success
        // 101 : Error
        byte[] sending_continue_hex = new byte[BLE.DEFAULT_BYTES_IN_CONTINUE_PACKET];
        for (int time = 0; time <= times; time++) {
            /**
             * Wait second before sending continue packet 
             */
            try {
                Thread.sleep(200);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }

            if (time == times) {
                Log.i(TAG, "LAST PACKET ");

                /**
                 * If you do not have enough characters to send continue packet,
                 * This is the last packet that will be sent to the band
                 */

                /**
                 * Packet length byte :
                 */
                /**
                 * Length of last packet
                 */
                int character_length = CHARACTERS.length()
                        - BLE.DEFAULT_BYTES_IN_CONTINUE_PACKET*times;

                initial_packet[1] = Byte.valueOf(String.valueOf(character_length
                        + BLE.INITIAL_MESSAGE_PACKET_LENGTH));
                initial_packet[2] = BLE.SENDING_LAST_PACKET;

                Log.i(TAG, "character_length " + character_length);

                /**
                 * Message
                 */
                // Hex file
                byte[] sending_last_hex = new byte[character_length];

                // Hex file : Get next bytes
                for (int i = 0; i < sending_last_hex.length; i++) {
                    sending_last_hex[i] = 
                            CHARACTERS.getBytes()[sending_continue_hex.length*time + i];
                }

                // Merge byte[]
                byte[] last_packet = 
                        new byte[character_length + BLE.INITIAL_MESSAGE_PACKET_LENGTH];
                System.arraycopy(initial_packet, 0, last_packet,
                        0, initial_packet.length);
                System.arraycopy(sending_last_hex, 0, last_packet, 
                        initial_packet.length, sending_last_hex.length);

                // Set value for characteristic
                characteristic.setValue(last_packet);
            } else {
                Log.i(TAG, "CONTINUE PACKET ");
                /**
                 * If you have enough characters to send continue packet,
                 * This is the continue packet that will be sent to the band
                 */
                /**
                 * Packet length byte
                 */
                int character_length = sending_continue_hex.length;

                /**
                 * TODO Default Length : 20 Bytes
                 */
                initial_packet[1] = Byte.valueOf(String.valueOf(
                        character_length + BLE.INITIAL_MESSAGE_PACKET_LENGTH));

                /**
                 * If sent data length > 20 bytes (Default : BLE allow send 20 bytes one time)
                 * -> set 01 : continue sending next packet
                 * else or if after sent until data length < 20 bytes
                 * -> set 00 : last packet
                 */
                initial_packet[2] = BLE.SENDING_CONTINUE_PACKET;
                /**
                 * Message
                 */
                // Hex file : Get first 17 bytes
                for (int i = 0; i < sending_continue_hex.length; i++) {
                    Log.i(TAG, "Send stt : " 
                            + (sending_continue_hex.length*time + i));

                    // Get next bytes
                    sending_continue_hex[i] = 
                            CHARACTERS.getBytes()[sending_continue_hex.length*time + i];
                }

                // Merge byte[]
                byte[] sending_continue_packet = 
                        new byte[character_length + BLE.INITIAL_MESSAGE_PACKET_LENGTH];
                System.arraycopy(initial_packet, 0, sending_continue_packet, 
                        0, initial_packet.length);
                System.arraycopy(sending_continue_hex, 0, sending_continue_packet, 
                        initial_packet.length, sending_continue_hex.length);

                // Set value for characteristic
                characteristic.setValue(sending_continue_packet);
            }

            // Write characteristic via BLE
            mBluetoothGatt.writeCharacteristic(characteristic);
        }
    }

public boolean writeCharacteristic(BluetoothGattCharacteristic characteristic,
            String data) {
        if (mBluetoothAdapter == null || mBluetoothGatt == null) {
            Log.w(TAG, "BluetoothAdapter not initialized");
            return false;
        }

        if (ActivityBLEController.IS_FIRST_TIME) {
            /**
             * In the first time, 
             * should send the Title
             */
            byte[] merge_title = sendTitle(data);

            // Set value for characteristic
            characteristic.setValue(merge_title);

            // Write characteristic via BLE
            mBluetoothGatt.writeCharacteristic(characteristic);

            // Reset
            ActivityBLEController.IS_FIRST_TIME = false;

            return true;
        } else {
            /**
             * In the second time, 
             * should send the Message
             */
            if (data.length() <= BLE.LIMIT_CHARACTERS) {
                sendMessage(characteristic, data);

                // Reset
                ActivityBLEController.IS_FIRST_TIME = true; 

                return true;
            } else {
                // Typed character
                typed_character = data.length();

                return false;
            }
        }
    }

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