Develop Reference

RN-42 + Android Receive Message Issues

I am building an Android application to communicate with my NR-42 bluetooth device. I am able to connect to the bluetooth and send data to the device which is a PIC18F but I am not able to receive bluetooth data from my device to my android phone.
I am following this example http://solderer.tv/data-transfer-between-android-and-arduino-via-bluetooth/comment-page-1/
When I use tera-term it shows me that the bluetooth module is doing what it is suppose to do, but I can't get the data in my textViews. I am trying to send float data. I am new to android but the issue is happening here I assume.
h = new Handler() {
public void handleMessage(android.os.Message msg) {
switch (msg.what) {
case RECIEVE_MESSAGE: // if receive massage
byte[] readBuf = (byte[]) msg.obj;
String strIncom = new String(readBuf, 0, msg.arg1); // create string from bytes array
sb.append(strIncom); // append string
int endOfLineIndex = sb.indexOf("\r\n"); // determine the end-of-line
if (endOfLineIndex > 0) { // if end-of-line,
String sbprint = sb.substring(0, endOfLineIndex); // extract string
sb.delete(0, sb.length()); // and clear
txtArduino.setText("Data from Arduino: " + sbprint); // update TextView
btnOff.setEnabled(true);
btnOn.setEnabled(true);
}
//Log.d(TAG, "...String:"+ sb.toString() + "Byte:" + msg.arg1 + "...");
break;
}
};
};
"
The input stream is being read here."
public void run() {
byte[] buffer = new byte[256]; // buffer store for the stream
int bytes; // bytes returned from read()
// Keep listening to the InputStream until an exception occurs
while (true) {
try {
// Read from the InputStream
bytes = mmInStream.read(buffer); // Get number of bytes and message in "buffer"
h.obtainMessage(RECIEVE_MESSAGE, bytes, -1, buffer).sendToTarget(); // Send to message queue Handler
Log.d(TAG, "sent handler");
} catch (IOException e) {
break;
}
}
}
Has anyone come across this issue or can help me out?
Thanks

Writing a bluetooth input stream to a file skips data

I am trying to write an app that will log the output of an arduino Due to a text file on the phone or tablet. The output rate is 1kHz. I have based my app on the Blueserial code (https://github.com/plastygrove/BlueSerial). The bluetooth connection gets established properly with the arduino bluetooth module, the commands are sent and received properly and everything seems to work just fine. However, the file that I am saving the data to is missing blocks of data, usually around 200ms worth every so often (I have a millisecond timestamp included in my data), resulting in corrupted data. I have been trying to figure out the source of the problem and I think it might be related to the gc but at this point I am at a loss. This is the code that writes my data to the file:
private class ReadInput implements Runnable {
private boolean bStop = false;
private Thread t;
public ReadInput() {
t = new Thread(this, "Input Thread");
t.start();
}
public boolean isRunning() {
return t.isAlive();
}
public void run() {
InputStream inputStream;
try {
inputStream = mBTSocket.getInputStream();
BufferedInputStream bis = new BufferedInputStream(inputStream);
while (!bStop) {
byte[] buffer = new byte[250];
int bytes = 0;
if (bis.available() > 0) {
bytes = bis.read(buffer);
strInput = new String(buffer, 0, bytes);
sb.append(strInput);
int endOfLineIndex = sb.indexOf("\r\n"); // determine the end-of-line
pw.print(strInput); // print buffer to the file buffer
pw.flush(); // flush buffer and force write to media
if (endOfLineIndex > 0) { // if end-of-line,
String sbprint = sb.substring(0, endOfLineIndex); // extract string
sb.delete(0, sb.length()); // and clear the string
pw.print(strInput); // write buffer to file buffer
pw.flush(); // force writing to file
pw.close(); // close print writer
try {
f.close(); // close file output stream
} catch (IOException e) {
e.printStackTrace();
}
}
sb.delete(0, sb.length()); strInput = "";
}
//Thread.sleep(100);
}
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
public void stop() {
bStop = true;
}
}
and this is my file outputsteam and printwriter declarations:
String strInput = null;
static PrintWriter pw = null;
static FileOutputStream f = null;
private StringBuilder sb = new StringBuilder();
The data I am sending is formatted as so:
24.330,-58,5,119,460\n
24.331,-86,25,-105,460\n
24.332,66,41,-145,460\n
24.333,90,-23,-85,4622,-7,119,460\n
24.524,6,-95,107,461\n
24.525,10,-7,-173,461\n
24.526,-22,33,103,461\n
and in this example you can see where it skipped some data. Thank you for helping out!

There appears to be code missing or you have some extra logic.
For example the StringBuilder doesn't appear to be doing anything,
bStop is never set/cleared. But you are always printing out the incoming data
via strInput.
The end of line handling also looks off, specifically this:
String sbprint = sb.substring(0, endOfLineIndex); // extract string
sb.delete(0, sb.length());
You extract the string and then delete the whole buffer sb.delete(0,sb.length())
same at the bottom of the loop.

Thread to catch a BluetoothSocket InputStream.read() timeout

I have been using InputStream.read( byte[] b, int off, int len ) method to read in data, but now have run into a timeout problem. I am sometimes expecting timeouts from reading, and should have the program adjust itself accordingly after a timeout. I have tried to implement a Thread but I really know nothing about Threads and cannot get it to work. I also want to add that this thread is being initialized within another thread. I'm not sure what the implications of this are but it may cause a problem.
My initial code had worked for the majority of times I need to read, but whenever I'm expecting a timeout, my program freezes at the read() call and never times out. When I implemented this new code, the times when my initial code worked now time out. I use Thread.wait(500) which I assume is 500 milliseconds, but I cannot find any Javadocs including the wait() function. Here and Here.
Other posts relating to this: 1, 2, 3.
I have also looked into declaring a timeout for the BluetoothSocket, but I cannot find it anywhere in the documentation.
Here is what my initial code looks like:
public void run(int length) throws IOException {
buffer = new byte[1024];
try {
bytes = mmInStream.read(buffer, 0, length);
mHandler.obtainMessage(MainMenu.MESSAGE_READ, bytes, -1, buffer)
.sendToTarget();
} catch (IOException e) {
Message msg = mHandler.obtainMessage(MainMenu.MESSAGE_TOAST);
Bundle bundle = new Bundle();
bundle.putString( TOAST, "Device has disconnected from the Bluetooth Module." );
msg.setData(bundle);
mHandler.sendMessage(msg);
connectionLost();
BluetoothService.this.start();
}
This is what I have tried to implement:
public void run(int length) throws IOException {
buffer = new byte[1024];
length1 = length;
Thread myThread = new Thread(new Runnable() {
public void run() {
try {
bytes = mmInStream.read( buffer, 0, length1 );
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
});
synchronized (myThread) {
myThread.start();
try {
myThread.wait(500);
if(myThread.isAlive()) {
mmInStream.close();
Log.i( "InStream", "Timeout exceeded!");
}
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
try {
myThread.run();
mHandler.obtainMessage(MainMenu.MESSAGE_READ, bytes, -1, buffer)
.sendToTarget();
} catch (IOException e) {
Message msg = mHandler.obtainMessage(MainMenu.MESSAGE_TOAST);
Bundle bundle = new Bundle();
bundle.putString( TOAST, "Device has disconnected from the Bluetooth Module." );
msg.setData(bundle);
mHandler.sendMessage(msg);
connectionLost();
BluetoothService.this.start();
}
EDIT:
So I'm trying to recreate
buffer = new byte[1024];
bytes = mmInStream.read(buffer, 0, length);
I have done the following:
Scanner scan = new Scanner(new InputStreamReader(mmInStream));
String readIn;
try {
readIn = scan.next();
bytes = 5; // I tried with or without this, since I do not think it matters...
buffer = readIn.getBytes( Charset.forName( "US-ASCII" ) );
}
Later in my code I make this call....Sorry edit again, the buf=read( 5 ) call goes to what is shown above.
byte[] buf = buffer;
write( a );
buf = read( 5 );
Log.i(TAG, "Before buf[5]" );
try {
buf[5] = '\0';
} catch( NullPointerException e ) {
return false;
}
When I use the original method, It passes this buf[5] call fine. But when I use the new method, it gives me an IndexOutOfBoundsException at that spot. Am I missing something? The expected input should be CMD\r\n

The bluetooth chat example is really poor in this respect, you should use an input scanner instead of mmInStream.read. Here's what I use and it works reasonably well...
For your use case you skip the entire buffer and byte and write and read (no need to use any of those when you are using a scanner and inputstreamreader as those handle that stuff for you)... in other words the below code takes care of all that for you. I changed the delimiter for you to CRLF. What the code below does is you send a string and it writes it and then reads. If you don't need to send anything to the remote device, just start at scan = new Scanner. Each time a line is read and it ends with \r\n it will store it in the string instring.
So if you want to send "a", you would write
String readIn = beginListenForData("a");
The a will be sent under the mmOutStream and then the scanner will read the mmInStream and collect all the characters, then once it sees a CRLF it will return the characters it read and return them in your readIn string. Make sense?
private String beginListenForData(String msg0) {
msg0 += "\r"; //this adds a return character to the string, you can omit this if you just send an a and the remote device understands what that means.
String instring = "";
try {
mmOutStream.write(msg0.getBytes());
} catch (IOException ex) {
stop();
}
scan = new Scanner(new InputStreamReader(mmInStream));
scan.useDelimiter(Pattern.compile("[\\r\\n]+"));
instring = scan.next();
scan = null;
return instring;
}

My bluetooth connexion is reading only zeros

From my Android phone, I'm trying to read (using Bluetooth) incomming strings from an external GPS device. I've followed mainly the BluetoothChat example and everything seems to work as expected so far. My reading thread is executing and I can see variable bytes packets incoming when looping with the following code:
Log.d(TAG, "BEGIN mConnectedThread");
byte[] buffer = new byte[1024];
int bytes;
// Keep listening to the InputStream while connected
while (true)
{
try
{
bytes = mmInStream.read(buffer);
// Test...
String strReadBuf = new String(buffer, 0, bytes);
// Send the obtained bytes to the UI Activity
mHandler.obtainMessage(BluetoothHandler.MessageType.READ,
bytes, buffer).sendToTarget();
} catch (IOException e) {
Log.e(TAG, "disconnected", e);
sendErrorMessage(R.string.bt_connection_lost);
break;
}
}
The strings I'm supposed to read are text strings (NMEA format) but I'm reading only 0 and -32 bytes in my buffer array. Any idea why I'm getting this?

Log.d(TAG, "BEGIN mConnectedThread");
byte[] buffer = new byte[1024];
int bytes;
// Keep listening to the InputStream while connected
while (true)
{
try
{
bytes = mmInStream.read(buffer);
// Test...
//String strReadBuf = new String(buffer, 0, bytes);
//I've changed for
String strReadBuf = new String(buffer);
// Send the obtained bytes to the UI Activity
mHandler.obtainMessage(BluetoothHandler.MessageType.READ,
bytes, buffer).sendToTarget();
} catch (IOException e) {
Log.e(TAG, "disconnected", e);
sendErrorMessage(R.string.bt_connection_lost);
break;
}
}
I used the String constructor String(byte[]), where byte[] is the buffer deprecating the byte[] size. I've used many times and that works for me even if the buffer size changes over time.

How to detect EOF on android bluetooth file transfer?

I have implemented a bluetooth connection using the now-classic Google Bluetooth Chat code. However, I have a question which I just cannot seem to wrap my brain around.
The reading of the input stream goes something like this:
public void run() {
byte[] buffer = new byte[1024]; // buffer store for the stream
int bytes; // bytes returned from read()
// 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
mHandler.obtainMessage(MESSAGE_READ, bytes, -1, buffer)
.sendToTarget();
} catch (IOException e) {
break;
}
}
}
Now, that's fine if I was just printing out the characters I was receiving as in the original example. However, suppose I wanted to transfer an image file. I don't know the size of the file, so I cannot count the bytes received or anything like that. In my tests, I don't seem to be ever receiving a "-1" from the input stream, which appears to be the "norm" for reading from input streams. So how can I know that I have reached the end of the file that was being sent?
Thank you for your help and your time.

It seems Android bluetooth input streams never return -1.
I guess setup a simple protocol by sending file size in the first place and EOF signals at last will help.

No it does not. Android sends -1 only when the Socket is closed as far as I know. So a workaround could be to do a reconnect, but I was trying that for hours and did not get it working, since I do not understand this "special" Code here (copied from a Stackoverflow Thread) for setting up the socket:
BluetoothSocket tmp = null;
Log.d(TAG, "New Connection initialized");
Method m;
try {
m = device.getClass().getMethod("createRfcommSocket",
new Class[] { int.class });
tmp = (BluetoothSocket) m.invoke(device, 1);
} catch (Exception e) {
e.printStackTrace();
}
mmSocket = tmp;
This Socket only works, when my App is started for the first filetransfer. If I want to "Reconnect" with a completely new instantiated Object (and a new Socket created with that Code), the program freezes on the blocking method mmSocket.connect(). It seems like the Method never comes to an ending. This is driving me nuts...

Try
while ((bytes = mmInStream.read(buffer) != -1)
and see if that helps.

Try this:
public void run() {
byte[] buffer;
ArrayList<Integer> arr_byte = new ArrayList<Integer>();
while (true) {
try {
int data = mmInStream.read();
if(mmInStream.available()>0) {
arr_byte.add(data);
} else {
arr_byte.add(data);
buffer = new byte[arr_byte.size()];
for(int i = 0 ; i < arr_byte.size() ; i++) {
buffer[i] = arr_byte.get(i).byteValue();
}
Log.e("INPUT",new String(buffer));
mHandler.obtainMessage(MESSAGE_READ, bytes, -1, buffer)
.sendToTarget();
arr_byte = new ArrayList<Integer>();
}
} catch (IOException e) {
break;
}
}
}