了解蓝牙 rfcoom 原始数据

Question

我正在尝试构建一个使用 rfcomm 读取通过蓝牙服务发送的信息的应用程序。 该设备是硬度计（HT-6510A），不幸的是找不到设备数据格式的规格我遇到了一个奇怪的问题，我必须了解如何阅读这些信息。

01-11 17:47:28.940 11862-13447/joinstore.it.testhardness V/result: ��S
01-11 17:47:29.581 11862-13447/joinstore.it.testhardness V/result: ��S
01-11 17:47:30.211 11862-13447/joinstore.it.testhardness V/result: ��S
01-11 17:47:30.872 11862-13447/joinstore.it.testhardness V/result: ��S
01-11 17:47:31.513 11862-13447/joinstore.it.testhardness V/result: ��S
01-11 17:47:32.143 11862-13447/joinstore.it.testhardness V/result: ��T
01-11 17:47:32.794 11862-13447/joinstore.it.testhardness V/result: ��T

这是我从设备收到的数据，我认为在稳定 rfcomm 连接后仅使用此线程的实现没有问题。

    //After connection, handle data transfer
    private class ConnectedThread extends Thread {
        private final BluetoothSocket mmSocket;
        private final InputStream mmInStream;
        private final OutputStream mmOutStream;

        public ConnectedThread(BluetoothSocket socket) {
            mmSocket = socket;
            InputStream tmpIn = null;
            OutputStream tmpOut = null;

            // Get the input and output streams, using temp objects because
            // member streams are final
            try {
                tmpIn = socket.getInputStream();
                tmpOut = socket.getOutputStream();
            } catch (IOException e) {
            }

            mmInStream = tmpIn;
            mmOutStream = tmpOut;
        }

        public void run() {
//            readAndPublishRaw();
            readAndPublishString();
            Log.v("result", "Reading data ended.");
            setStatusText(-1);
        }

        void readAndPublishRaw(){
            byte[] buffer = new byte[1024];  // buffer store for the stream
            int bytes; // bytes returned from read()
            Log.v("result", "Start reading...");
            // Keep listening to the InputStream until an exception occurs
            while (true) {
                try {
                    // Read from the InputStream
                    bytes = mmInStream.read(buffer);
                    // Send the obtained bytes to the UI activity
                    Log.v("result", bytes + "");
                } catch (IOException e) {
                    break;
                }
            }
        }

        void readAndPublishString(){
            //String method, not useful in this case?
            try {
                BufferedReader r = new BufferedReader(new InputStreamReader(mmInStream));
                StringBuilder total = new StringBuilder();
                String line;
                Log.v("result", "Start reading...");
                while ((line = r.readLine()) != null) {
                    total.append(line);
                    Log.v("result", line);
                }
                Log.v("result", total.toString());
                //TODO publish read string to the view
            } catch (Exception e) {
                //
                try {
                    mmSocket.close();
                }catch (Exception ex){}
                Log.v(TAG, "exception reading data from service");
            }
        }

        /* Call this from the main activity to send data to the remote device */
        public void write(byte[] bytes) {
            try {
                mmOutStream.write(bytes);
            } catch (IOException e) {
            }
        }

        /* Call this from the main activity to shutdown the connection */
        public void cancel() {
            try {
                mmSocket.close();
                setStatusText(-1);
            } catch (IOException e) {
            }
        }
    }

你们能给我有关如何正确解析这些原始数据的任何信息吗？我想我应该有一个浮点值流，但我只是这些随机的东西。

Answer 1

关于如何首先获得一些可用日志输出的建议：

    void readAndPublishRaw(){
        byte[] buffer = new byte[1024];  // buffer store for the stream
        int bytes; // bytes returned from read()
        Log.v("result", "Start reading...");
        // Keep listening to the InputStream until an exception occurs
        while (true) {
            try {
                // Read from the InputStream
                bytes = mmInStream.read(buffer);
                // Send the obtained bytes to the UI activity

              final StringBuilder sb = new StringBuilder();
              sb.append("Received ").append(bytes).append(" bytes: ");
              for ( int i = 0; i < bytes; i++ ) {
                sb.append( Integer.toHexString(((int)buffer[i]) & 0xff) ).append(", ");
              }

              Log.v("result", sb.toString());
            } catch (IOException e) {
                break;
            }
        }
    }

下一步应该是校准数据，即记下哪个输入/显示值会产生什么原始数据。从那里，您可能无法推断出实际的编码。

除了数据中的实际测量值之外，您的设备可能包含也可能不包含其他信息，例如指示电池电量低。必须将其分解才能获得原始测量值。

如果一个数据值包含多个字节，则需要确定字节顺序（小端或大端）。

小型设备的浮点数据通常以定点表示。有时，尤其是。如果也需要负数，则添加偏移量，以便

realValue = rawValue * a + c

如果你发现 a 和 c 你很好。因此，一旦您从上面完成的校准中只能关联两个不同的realValues 和对应的rawValues，您就有足够的数据来求解a 和c 的方程。

具有更多“冲击力”的设备，例如嵌入式 linux 设备，也可以使用常规的IEEE floating point data。 - 并不是说​​小型嵌入式设备不能使用 IEEE，而是浮点数通常超出了要求，而且浮点仿真代码的复杂性（内存和 CPU）更高。