OBDKey Bluetooth

Question

Hello, Can you help me
I want to connect my Motorola droid to OBDKey by bluetooth. I use Bluetooth Chat as for example to bluetooth connect, KWP as protocol

Then I write byte[] command

    command[0]=rawToByte(0x02);
 command[1]=rawToByte(0x85);
 command[2]=rawToByte(0x05);
 command[3]=rawToByte(0xc7);
 command[4]=rawToByte(0x33);
 command[5]=rawToByte(0xf1);
 command[6]=rawToByte(0x00);
 command[7]=rawToByte(0x00);
 command[8]=rawToByte(0x00);
 command[9]=rawToByte(0x00);
 command[10]=rawToByte(0x00);
 command[11]=rawToByte(0x00);
 command[12]=rawToByte(0x00);
 command[13]=rawToByte(0x00);
 command[14]=rawToByte(0x76);

where function "rawToByte" is:

public static byte rawToByte(int b) { return (byte) (0xff & b); }

In the result OBDKey sent to device byte 0x02 This value is the first command, so it copy value

What did I do wrong?

Answer 1

The OBDKey is an ELM327 based bluetooth OBD adapter. It's just like the DealExtreme and scantool.net bluetooth adapters as far as features and method of use. I'm quite familiar with the latter two.

Here's how to send a string to the device, assuming you already opened the socket and stream, and the output socket is named mBTOutputStream

/**
 * Send the exact string provided. 
 * We don't append a CRLF or anything like that - we just send the exact string to the device as-is. 
 * @param sendThis - exact string to send to the device. 
 * @return - returns true unless a problem occurs, in which case we return false;
 */
public boolean sendRaw(String sendThis) {

        // Ya can't send data if we're not connected!
        if (isConnected() != true)
                return false;

        byte bsendThis[] = sendThis.getBytes();

        try {mBTOutputStream.write(bsendThis);} catch (Exception e) {
                ioErrorOccurredDuringOutput();
                return false;
        }

        ioResetOutputErrorCount();
        return true;
}

Also remember to also read from the device, otherwise the input buffer will become full and start blocking I/O.

Answer 2

This is my part of testing code. Before this my Motorola was paired and connected to OBDKey

/** * This thread runs during a connection with a remote device. * It handles all incoming and outgoing transmissions. */ private class ConnectedThread extends Thread {

    private final InputStream mmInStream;
    private final OutputStream mmOutStream;

    public ConnectedThread(BluetoothSocket socket) {
        Log.d(TAG, "create ConnectedThread");
        mmSocket = socket;
        InputStream tmpIn = null;
        OutputStream tmpOut = null;

        // Get the BluetoothSocket input and output streams
        try {
            tmpIn = socket.getInputStream();
            tmpOut = socket.getOutputStream();
        } catch (IOException e) {
            Log.e(TAG, "temp sockets not created", e);
        }

        mmInStream = tmpIn;
        mmOutStream = tmpOut;
    }

    public void run() {
        Log.i(TAG, "BEGIN mConnectedThread");
        byte[] buffer = new byte[32];
        int bytes;

        // Keep listening to the InputStream while connected
        while (true) {
            try {
                // Read from the InputStream
                bytes = mmInStream.read(buffer);

                // Send the obtained bytes to the UI Activity
                mHandler.obtainMessage(BluetoothChat.MESSAGE_READ, bytes, -1, buffer)
                        .sendToTarget();
            } catch (IOException e) {
                Log.e(TAG, "disconnected", e);
                connectionLost();
                break;
            }
        }
    }

/** * Write to the connected OutStream. * @param buffer The bytes to write */ public void write(byte[] buffer) { try { mmOutStream.write(buffer);

            // Share the sent message back to the UI Activity
            mHandler.obtainMessage(BluetoothChat.MESSAGE_WRITE, -1, -1, buffer)
                    .sendToTarget();
        } catch (IOException e) {
            Log.e(TAG, "Exception during write", e);
        }
    }

    public void cancel() {
        try {
            mmSocket.close();
        } catch (IOException e) {
            Log.e(TAG, "close() of connect socket failed", e);
        }
    }

/** * Write to the ConnectedThread in an unsynchronized manner * @param out The bytes to write * @see ConnectedThread#write(byte[]) */ public void write(byte[] out) { // Create temporary object ConnectedThread r; // Synchronize a copy of the ConnectedThread synchronized (this) { if (mState != STATE_CONNECTED) return; r = mConnectedThread; } // Perform the write unsynchronized r.write(out); }

I use function "write" to write commands[]. In the rezult it writes bytes, but it reads not corect .

For example, if I send such bytes 02 01 03 it will read 02

if I send such bytes 1C 01 05 it will read 1C

What did I do wrong? Is this a problem with connect to OBDKey or with wrong send byte[] to OBDKey?