Android Studio communicating with HID USB device with controlTransfer - java

I'm having issues communicating with a HID USB device in Android Studio.
I have code in Python which works perfectly, so the device is fine.
Also note, that I've used this java class for another device where I receive data only and it works wonderfully.
But this new device, I need to send and receive data. So I am using controlTransfer to send data on endpouint 0.
Here's the code (snippets) in Python:
import hid
DEVICEMODE = 0x0B
GBLINK = 0x02
self.dongle = hid.device()
self.dongle.open(self.idVendor, self.idProduct)
self.sendCommand(0, DEVICEMODE, 0x00, 0x01)
self.sendCommand(0, GBLINK, 0x40, 0xFF)
def sendCommand(self, pucknum, cmd, msb, lsb):
command = (0b11000000 & (devicenum << 6)) | cmd
self.dongle.set_nonblocking(1)
self.dongle.write([0x00, command, msb, lsb]) # first byte is report id
self.dongle.set_nonblocking(0)
The code then goes on to send various commands via the sendCommand method.
In Java, I have the following
public class DongleDevice implements Runnable {
protected final String TAG = "DongleDevice";
public UsbDevice usbDevice;
public UsbManager usbManager;
public UsbDeviceConnection usbDeviceConnection;
private UsbInterface intf;
private UsbEndpoint endpoint;
public int version = -1;
public Thread thread;
public volatile boolean threadRunning = false;
private boolean status = false;
private boolean firstTime = true;
private UsbRequest request = null;
public DongleDevice() {
thread = new Thread(this);
}
public void requestPermission() {
usbManager = (UsbManager) context.getSystemService(Context.USB_SERVICE);
HashMap<String, UsbDevice> deviceList = usbManager.getDeviceList();
Iterator<UsbDevice> deviceIterator = deviceList.values().iterator();
deviceFound = false;
deviceReady = false;
while (deviceIterator.hasNext()) {
usbDevice = deviceIterator.next();
if (usbDevice.getVendorId() == Constants.VENDOR_ID) {
deviceFound = true;
break;
}
}
if (deviceFound == true) {
PendingIntent pi = PendingIntent.getBroadcast(context, 0, new Intent("PERMISSION_GRANTED"), 0);
usbManager.requestPermission(usbDevice, pi);
}
}
public void openDevice () {
final Handler handler = new Handler();
boolean handlePlaced = handler.postDelayed(new Runnable() {
public void run() {
usbManager = (UsbManager) context.getSystemService(Context.USB_SERVICE);
HashMap<String, UsbDevice> deviceList = usbManager.getDeviceList();
Iterator<UsbDevice> deviceIterator = deviceList.values().iterator();
deviceFound = false;
deviceReady = false;
while (deviceIterator.hasNext()) {
usbDevice = deviceIterator.next();
if (usbDevice.getVendorId() == Constants.VENDOR_ID) {
deviceFound = true;
break;
}
}
if (deviceFound == true) {
if (usbManager.hasPermission(usbDevice)) open();
else closeDevice();
}
}
}, 2000);
}
private void open() {
endpoint = intf.getEndpoint(0);
usbDeviceConnection = usbManager.openDevice(usbDevice);
status = usbDeviceConnection.claimInterface(intf, true);
if (status) {
getVersion();
thread.start();
} else {
closeDevice();
}
}
private void getVersion() {
byte[] rawDescriptors;
rawDescriptors = usbDeviceConnection.getRawDescriptors();
version = (int)(rawDescriptors[12] & 0x01);
}
public void closeDevice() {
deviceReady = false;
deviceFound = false;
if (threadRunning == true) {
if (request != null) {
request.cancel();
}
}
}
public void onDestroy() {
closeDevice();
}
public boolean isOpen() {
return deviceFound;
}
#Override
public void run() {
threadRunning = true;
deviceReady = true;
ByteBuffer buffer = ByteBuffer.allocate(60);
if (request != null) request.cancel();
request = new UsbRequest();
status = request.initialize(usbDeviceConnection, endpoint);
P_Device pd1 = new P_Device(0); //a class for parsing the 60 byte data packet received
byte[] command;
int response;
int requestType = 0x21;
int requestId = 0x9;
int value = 0x200; // 0x300 also works
int index = 0;
int timeout = 5000;
byte DEVICEMODE = 0x0B;
byte GBLINK = 0x02;
while (deviceFound == true) {
command = new byte[] {DEVICEMODE, 0x00, 0x01}; // send command followed by two bytes
response = usbDeviceConnection.controlTransfer(requestType, requestId, value, index, command, command.length, timeout);
Logger.d(TAG,"controlTransfer response = " + response); // I get 3 as a response
try { thread.sleep(100); } catch (Exception e) { }
for (int i=0; i<20; i++) {
command = new byte[]{GBLINK, (byte) 64, (byte) 255}; // should blink for ~300 ms at full intensity
response = usbDeviceConnection.controlTransfer(requestType, requestId, value, index, command, command.length, timeout);
Logger.d(TAG, "controlTransfer response = " + response); // I get 3 as a response
try { thread.sleep(500); } catch (Exception e) { }
}
for (int i=0; i<20; i++) {
request.queue(buffer, 60);
if (usbDeviceConnection.requestWait().equals(request)) {
//buffer.flip();
buffer.position(0);
pd1.parse(buffer) // all results are 0, and they shouldn't be.
}
try { thread.sleep(100); } catch (Exception e) { }
}
command = new byte[] {DEVICEMODE , 0x00, 0x00};
response = usbDeviceConnection.controlTransfer(requestType, requestId, value, index, command, command.length, timeout);
Logger.d(TAG,"controlTransfer response = " + response); // I get 3 as a response
try { thread.sleep(100); } catch (Exception e) { }
deviceFound = false;
}
threadRunning = false;
deviceReady = false;
}
}
When I run my code I get the confirmation that the bytes sent are 3 (a -1 would indicate an error). But the device isn't blinking as it should, and I get all 0's from the read.
Any help would be appreciated.

Related

Cannot send and receive any data from bluetooth

I have an simple sender/receiver android app based on bluetooth. Connection between two phone is succesfully created. But data is not sending and receiving.
Code what I tried :
public class MainActivity extends Activity
{
TextView myLabel;
EditText myTextbox;
BluetoothAdapter mBluetoothAdapter;
BluetoothSocket mmSocket;
BluetoothDevice mmDevice;
OutputStream mmOutputStream;
InputStream mmInputStream;
Thread workerThread;
byte[] readBuffer;
int readBufferPosition;
volatile boolean stopWorker;
void findBT()
{
mBluetoothAdapter = BluetoothAdapter.getDefaultAdapter();
if(mBluetoothAdapter == null)
{
myLabel.setText("No bluetooth adapter available");
}
if(!mBluetoothAdapter.isEnabled())
{
Intent enableBluetooth = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);
startActivityForResult(enableBluetooth, 0);
}
Set<BluetoothDevice> pairedDevices = mBluetoothAdapter.getBondedDevices();
if(pairedDevices.size() > 0)
{
for(BluetoothDevice device : pairedDevices)
{
String deviceName = device.getName();
deviceName=deviceName.replaceAll("[^A-Za-z]+", "");
//String deviceHardwareAddress = device.getAddress(); // MAC address
Log.i("## name : ",deviceName+" ");
if(deviceName.equals("GalaxyTabAwithSPen")) {
mmDevice = device;
break;
}
}
}
// tel GalaxyTabAwithSPen
// tablet GhhBbbGalaxyS
}
void openBT()
{
if(mmDevice==null)
Log.i("test","notnull");
ParcelUuid list[] = mmDevice.getUuids();
for(ParcelUuid x: list){
System.out.println(x.toString());
}
Log.i("size :"+list.length," "+list[1].toString());
UUID uuid = UUID.fromString(list[1].toString()); //Standard SerialPortService ID
//UUID uuid = UUID.fromString("00001101-0000-1000-8000-00805F9B34FB");
try {
mmSocket = mmDevice.createRfcommSocketToServiceRecord(uuid);
mmSocket.connect();
mmOutputStream = mmSocket.getOutputStream();
mmInputStream = mmSocket.getInputStream();
beginListenForData();
myLabel.setText("Bluetooth Opened");
}
catch (Exception ex){
Log.i("IO ex : ", ex.getMessage());
}
}
void beginListenForData()
{
final Handler handler = new Handler();
final byte delimiter = 10; //This is the ASCII code for a newline character
stopWorker = false;
readBufferPosition = 0;
readBuffer = new byte[1024];
workerThread = new Thread(new Runnable()
{
public void run()
{
while(!Thread.currentThread().isInterrupted() && !stopWorker)
{
try
{
int bytesAvailable = mmInputStream.available();
if(bytesAvailable > 0)
{
byte[] packetBytes = new byte[bytesAvailable];
mmInputStream.read(packetBytes);
for(int i=0;i<bytesAvailable;i++)
{
byte b = packetBytes[i];
if(b == delimiter)
{
byte[] encodedBytes = new byte[readBufferPosition];
System.arraycopy(readBuffer, 0, encodedBytes, 0, encodedBytes.length);
final String data = new String(encodedBytes, "US-ASCII");
readBufferPosition = 0;
handler.post(new Runnable()
{
public void run()
{
myLabel.setText(data);
}
});
}
else
{
readBuffer[readBufferPosition++] = b;
}
}
}
}
catch (IOException ex)
{
Log.i("IO ex read " ,ex.getMessage());
stopWorker = true;
}
}
}
});
workerThread.start();
}
void sendData() throws IOException
{
String msg = myTextbox.getText().toString();
msg += "\n";
mmOutputStream.write(msg.getBytes());
myLabel.setText("Data Sent");
}
When I click open both tablet and mobile phone, myLabel text changed to "Blueetooth Opened" succesfully.
But when I try to send text to phone from tablet or to table from phone, nothing sended. Data listener is working. mmInputStream.available() always returns 0.
Some log details :
D/BluetoothUtils: isSocketAllowedBySecurityPolicy start : device null
W/BluetoothAdapter: getBluetoothService() called with no BluetoothManagerCallback
D/BluetoothSocket: connect(), SocketState: INIT, mPfd: {ParcelFileDescriptor: FileDescriptor[49]}

Android read string via USB communication

I do not have much experience with USB connection in Android, so I followed the tutorial on the Android developer page. I tried to put together a code, which when I send a command to a USB device, for example
send("M?");
then the device sends me back some rows of string which my app processes and displays it to me. But unfortunately I do not get what I want. Sometimes I get just a part of that string, sometimes some strange characters, or nothing. Could you please help me, how to fix my code? This code should be able to read small strings(for example 20-25 characters) but also long strings.
I have the following code:
UsbReadWrite.java
public class UsbReadWrite extends AppCompatActivity {
static UsbDevice device;
private static final String ACTION_USB_PERMISSION = "com.android.example.USB_PERMISSION";
static UsbManager mUsbManager;
static PendingIntent mPermissionIntent;
private static byte[] bytes;
private static boolean forceClaim = true;
static int controlTransferResult;
static byte[] readBytes = new byte[4096];
static UsbEndpoint epOut = null, epIn = null;
static UsbDeviceConnection connection;
static int recvBytes;
static String readString = "";
static Thread thread;
static Runnable r;
static UsbInterface intf;
static UsbRequest request;
Handler handler;
static UsbManager manager;
static HashMap<String, UsbDevice> deviceList;
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
}
public UsbReadWrite(Handler handler){
this.handler = handler;
}
public static boolean connectDevice(Context context){
manager = (UsbManager) context.getSystemService(Context.USB_SERVICE);
deviceList = manager.getDeviceList();
if (deviceList.toString().equals("{}")) {
return false;
}
Iterator<UsbDevice> deviceIterator = deviceList.values().iterator();
device = deviceIterator.next();
mUsbManager = (UsbManager) context.getSystemService(Context.USB_SERVICE);
mPermissionIntent = PendingIntent.getBroadcast(context, 0, new Intent(ACTION_USB_PERMISSION), 0);
IntentFilter filter = new IntentFilter(ACTION_USB_PERMISSION);
try {
context.registerReceiver(mUsbReceiver, filter);
}catch (Exception e){
e.printStackTrace();
}
mUsbManager.requestPermission(device, mPermissionIntent);
intf = device.getInterface(0);
// look for our bulk endpoints
for (int i = 0; i < intf.getEndpointCount(); i++) {
UsbEndpoint ep = intf.getEndpoint(i);
if (ep.getType() == UsbConstants.USB_ENDPOINT_XFER_BULK) {
if (ep.getDirection() == UsbConstants.USB_DIR_OUT) {
epOut = ep;
} else if (ep.getDirection() == UsbConstants.USB_DIR_IN) {
epIn = ep;
}
}
}
if (epOut == null || epIn == null) {
throw new IllegalArgumentException("Not all endpoints found.");
}
Thread t = new Thread(new Runnable() {
#Override
public void run() {
while (!mUsbManager.hasPermission(device)){
try {
Thread.sleep(10);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
connection = mUsbManager.openDevice(device);
connection.claimInterface(intf, forceClaim);
connection.controlTransfer(0x40, 0, 0, 0, null, 0, 0);// reset
connection.controlTransfer(0x40, 0, 1, 0, null, 0, 0);// clear Rx
connection.controlTransfer(0x40, 0, 2, 0, null, 0, 0);// clear Tx
controlTransferResult = connection.controlTransfer(0x40, 0x03, 0x4138, 0, null, 0, 0);
connection.controlTransfer(0x40, 0x04, 0x0008, 0, null, 0, 0);
request = new UsbRequest();
request.initialize(connection, epOut);
}
});
t.start();
return true;
}
public static final BroadcastReceiver mUsbReceiver = new BroadcastReceiver() {
public void onReceive(Context context, Intent intent) {
String action = intent.getAction();
if (ACTION_USB_PERMISSION.equals(action)) {
synchronized (this) {
UsbDevice device = (UsbDevice) intent.getParcelableExtra(UsbManager.EXTRA_DEVICE);
if (intent.getBooleanExtra(UsbManager.EXTRA_PERMISSION_GRANTED, false)) {
if (device != null) {
//call method to set up device communication
intf = device.getInterface(0);
// look for our bulk endpoints
for (int i = 0; i < intf.getEndpointCount(); i++) {
UsbEndpoint ep = intf.getEndpoint(i);
if (ep.getType() == UsbConstants.USB_ENDPOINT_XFER_BULK) {
if (ep.getDirection() == UsbConstants.USB_DIR_OUT) {
epOut = ep;
} else if (ep.getDirection() == UsbConstants.USB_DIR_IN) {
epIn = ep;
}
}
}
if (epOut == null || epIn == null) {
throw new IllegalArgumentException("Not all endpoints found.");
}
connection = mUsbManager.openDevice(device);
connection.claimInterface(intf, forceClaim);
connection.controlTransfer(0x40, 0, 0, 0, null, 0, 0);// reset
connection.controlTransfer(0x40, 0, 1, 0, null, 0, 0);// clear Rx
connection.controlTransfer(0x40, 0, 2, 0, null, 0, 0);// clear Tx
controlTransferResult = connection.controlTransfer(0x40, 0x03, 0x4138, 0, null, 0, 0);
connection.controlTransfer(0x40, 0x04, 0x0008, 0, null, 0, 0);
request = new UsbRequest();
request.initialize(connection, epOut);
}
} else {
Log.d("MyActivity", "permission denied for device " + device);
}
}
}
}
};
public static void read2(){
r = new Runnable() {
#Override
public void run() {
synchronized (this) {
readString="";
send("M?");
while (true) {
try {
Thread.sleep(400);
} catch (InterruptedException e) {
e.printStackTrace();
}
if (mUsbManager.hasPermission(device)){
recvBytes = connection.bulkTransfer(epIn, readBytes, readBytes.length, 100);
Log.e("Database","M?="+readBytes);
if (recvBytes != 0) {
readString += new String(readBytes);
readString = readString.replace("\u0001`","");
readString = readString.replace("\u0000","");
Log.e("Database","M?="+readString);
}
}
}
}
}
};
thread = new Thread(r);
thread.start();
}
public static void send(String command){
String fullCommand = "#" + command + "\r\n"; /*+ "\r\n"*/
bytes = fullCommand.getBytes();
while (connection==null){
continue;
}
connection.bulkTransfer(epOut, bytes, bytes.length, 100); //0
}
}
Thanks in advance.

Accoure Error 500 when i use HttpClient of android?

I have below code and in this code i am using from HttpClient for connect to webservice .Net but when i using this, i get Error 500 from here Log.i("OK", Integer.toString(code)); but i need that when i get 200 i login to webSite and etc..
public class MainActivity extends Activity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Thread thread = new Thread(new Runnable() {
#Override
public void run() {
HttpClient client = new DefaultHttpClient();
HttpPost methodPost = new HttpPost("http://online.test.com/MobileWebService/Related.asmx/Login");
try {
HttpResponse response = client.execute(methodPost);
int code = response.getStatusLine().getStatusCode();
Log.i("OK", Integer.toString(code));
} catch (ClientProtocolException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
});
thread.start();
}
}
Notice 1 : ..../Login is a method in webService for login. It get 4 parameters .
Notice 2 : As the first step i should be sure that it is connected successfully (I mean I should get the "200") and then Login to webSite.
I don't like use KSOAP .
And below is my webService .Net:
[WebMethod(EnableSession = true)]
public int Login(string username, string pass, string device, int? security)
{
var ret = -3;
try
{
var bs = new BaseMaster();
if (!bs.securityRequest(10))
{
return -10;
}
bs.setLogMobileVisit();
if (string.IsNullOrEmpty(pass) || security == null || string.IsNullOrEmpty(username))
{
ret = -2;
}
else if (security != 128110)
{
ret = -1;
}
else
{
var user = GetUserByName(username);
var p = Hash.MD5(pass);
if (user != null && user.Hidden == false && user.Password == Hash.MD5(pass))
{
if (user.Firstname != device)
{
return -4;
}
var u = new UserDB();
u.LastLogDate = DateTime.Now;
u.UpdateDate = DateTime.Now;
u.UserID = user.UserID;
Makarem_Facade.MakaremFL.UpdateMobileUserDB(u);
ret = (int)user.UserID;
var pl = new PermissionDBList();
Security.Login(user,false,pl);
StartSession(user);
}
else if (user.Hidden == true)
{
ret = 0;
}
else if (user == null)
{
ret = -3;
}
else
{
ret = -5;
}
}
}
catch
{
ret = -6;
}
return ret;
}

Android Shoutcast internet Radio Streaming

I developed Shoutcastinternet Radio Streaming and I'm able to stream and play Successfully.
But the problem is: when i execute my application,I'm able to stream and play Continuously for halfanhour,after that the stream is getting stopped(not able to play, after that if i click on again play the stream Continues and again after some time FileNotFoundException)?
I logged the Error, after Stream get stopped.
The Error is :
java.io.FileNotFoundException: /data/data/com.torilt/cache/downloadingMediaFile430 (No such file or directory)
Can't find file. Android must have deleted it on a clean up
Getting Exception in setupplayer()
Source Code:
public class StreamingMediaPlayer extends Service {
final static public String AUDIO_MPEG = "audio/mpeg";
final static public String BITERATE_HEADER = "icy-br";
public int INTIAL_KB_BUFFER ;
private Handler handler;
//= 96*10/8
final public int BIT = 8;
final public int SECONDS = 60;
int bitrate = 56;
public File downloadingMediaFile;
final public String DOWNFILE = "downloadingMediaFile";
public Context context;
public int counter;
public int playedcounter;
public int preparecounter;
public MediaPlayer mp1;
public MediaPlayer mp2;
public boolean mp1prepared;
public boolean mp2prepared;
public boolean mp1preparing;
public boolean mp2preparing;
public boolean downloadingformp1;
public boolean downloadingformp2;
public boolean prepareState;
public String SONGURL = "";
// playing is "true" for mp1 and "false" for mp2
public boolean mp1playing;
public boolean started;
public boolean processHasStarted;
public boolean processHasPaused;
public boolean regularStream;
public BufferedInputStream stream;
public URL url;
public URLConnection urlConn;
public String station;
public String audiourl;
public Intent startingIntent = null;
public boolean stopping;
Thread preparringthread;
boolean waitingForPlayer;
// Setup all the variables
private void setupVars() {
counter = 0;
playedcounter = 0;
preparecounter = 0;
mp1 = new MediaPlayer();
mp2 = new MediaPlayer();
mp1prepared = false;
mp2prepared = false;
mp1preparing = false;
mp2preparing = false;
downloadingformp1 = false;
downloadingformp2 = false;
prepareState = true;
mp1playing = false;
started = false;
processHasStarted = false;
processHasPaused = true;
regularStream = false;
stream = null;
url = null;
urlConn = null;
station = null;
audiourl = null;
stopping = false;
preparringthread = null;
waitingForPlayer = false;
}
// This object will allow other processes to interact with our service
private final IStreamingMediaPlayer.Stub ourBinder = new IStreamingMediaPlayer.Stub() {
// String TAG = "IStreamingMediaPlayer.Stub";
public String getStation() {
// Log.d(TAG, "getStation");
return station;
}
public String getUrl() {
// Log.d(TAG, "getUrl");
return audiourl;
}
public boolean playing() {
// Log.d(TAG, "playing?");
return isPlaying();
}
public boolean pause() {
// Log.d(TAG, "playing?");
return isPause();
}
public void startAudio() {
// Log.d(TAG, "startAudio");
Runnable r = new Runnable() {
public void run() {
onStart(startingIntent, 0);
}
};
new Thread(r).start();
}
public void stopAudio() {
// Log.d(TAG, "stopAudio");
stop();
}
};
#Override
public void onCreate() {
super.onCreate();
context = this;
}
#Override
public void onStart(Intent intent, int startId) throws NullPointerException {
super.onStart(intent, startId);
// final String TAG = "StreamingMediaPlayer - onStart";
context = this;
setupVars();
if (intent.hasExtra("audiourl")) {
raiseThreadPriority();
processHasStarted = true;
processHasPaused = false;
audiourl = intent.getStringExtra("audiourl");
station = intent.getStringExtra("station");
downloadingMediaFile = new File(context.getCacheDir(), DOWNFILE+ counter);
downloadingMediaFile.deleteOnExit();
Runnable r = new Runnable() {
public void run() {
try {
startStreaming(audiourl);
} catch (IOException e) {
// Log.d(TAG, e.toString());
}
}
};
Thread t = new Thread(r);
t.start();
}
}
#Override
public void onDestroy() {
super.onDestroy();
mp1.stop();
mp2.stop();
}
#Override
public IBinder onBind(Intent intent) {
startingIntent = intent;
context = this;
return ourBinder;
}
#Override
public boolean onUnbind(Intent intent) {
super.onUnbind(intent);
stopSelf();
return true;
}
/**
* Progressivly download the media to a temporary location and update the
* MediaPlayer as new content becomes available.
*/
public void startStreaming(final String mediaUrl) throws IOException {
try {
url = new URL(mediaUrl);
urlConn = (HttpURLConnection) url.openConnection();
urlConn.setReadTimeout(1000 * 20);
urlConn.setConnectTimeout(1000 * 5);
//The getContentType method is used by the getContent method to determine the type of the remote object; subclasses may find it convenient to override the getContentType method.
String ctype = urlConn.getContentType();
if (ctype == null) {
ctype = "";
} else {
ctype = ctype.toLowerCase();
}
if (ctype.contains(AUDIO_MPEG) || ctype.equals("")) {
String temp = urlConn.getHeaderField(BITERATE_HEADER);
if (temp != null) {
bitrate = new Integer(temp).intValue();
}
} else {
stopSelf();
return;
}
}
catch(NullPointerException ne)
{
}
catch (IOException ioe) {
// Log.e(TAG, "Could not connect to " + mediaUrl);
stopSelf();
return;
}
if (!regularStream) {
INTIAL_KB_BUFFER = bitrate * SECONDS / BIT;
Runnable r = new Runnable() {
public void run() {
try {
downloadAudioIncrement(mediaUrl);
Log.i("TAG12344444", "Unable to play");
stopSelf();
return;
} catch (IOException e) {
Log.i("TAG123", "Unable to initialize the MediaPlayer for Audio Url = "+mediaUrl, e);
stopSelf();
return;
} catch (NullPointerException e) {
stopSelf();
return;
}
}
};
Thread t = new Thread(r);
t.start();
}
}
/**
* Download the url stream to a temporary location and then call the
* setDataSource for that local file
*/
public void downloadAudioIncrement(String mediaUrl) throws IOException{
int bufsizeForDownload = 8 * 1024;
int bufsizeForfile = 64 * 1024;
stream = new BufferedInputStream(urlConn.getInputStream(),bufsizeForDownload);
Log.i("bufsize",Integer.toString(urlConn.getInputStream().available()));
try{
if(stream == null || stream.available() == 0){
stopSelf();
Log.i("unable to create ","stream null");
return;
}
}catch (NullPointerException e) {
stopSelf();
Log.i("return1","return1");
return;
}
BufferedOutputStream bout = new BufferedOutputStream(new FileOutputStream(downloadingMediaFile), bufsizeForfile);
byte buf[] = new byte[bufsizeForDownload];
int totalBytesRead = 0, totalKbRead = 0, numread = 0;
do {
if (bout == null) {
counter++;
downloadingMediaFile = new File(context.getCacheDir(), DOWNFILE+ counter);
downloadingMediaFile.deleteOnExit();
bout = new BufferedOutputStream(new FileOutputStream(downloadingMediaFile), bufsizeForfile);
}
try {
numread = stream.read(buf);
} catch (IOException e) {
Log.d("Downloadingfile", "Bad read. Let's quit.");
// stop();
Log.i("return2","return2");
stopSelf();
// return;
}
catch (NullPointerException e) {
// Let's get out of here
e.printStackTrace();
break;
}
if (numread < 0) {
bout.flush();
stopSelf();
Log.i("Bad read from stream", "Bad read from stream3");
if(stream == null){
urlConn = new URL(mediaUrl).openConnection();
urlConn.setConnectTimeout(1000 * 30);
urlConn.connect();
stream = new BufferedInputStream(urlConn.getInputStream(),bufsizeForDownload);
}else{
handler.post(new Runnable() {
public void run() {
Log.i("Bad read from stream", "Bad read from xyz");
context.stopService(startingIntent);
Log.i("return3","return3");
return;
}
});
}
} else if (numread >= 1) {
bout.write(buf, 0, numread);
totalBytesRead += numread;
totalKbRead += totalBytesRead / 1000;
}
if (totalKbRead >= INTIAL_KB_BUFFER && stopping != true) {
bout.flush();
bout.close();
bout = null;
if (started == false) {
Runnable r = new Runnable() {
public void run() {
setupplayer();
}
};
Thread t = new Thread(r);
t.start();
}
totalBytesRead = 0;
totalKbRead = 0;
}
if (stopping == true) {
stream = null;
}
} while (stream != null);
}
/** oncompletelister for media player **/
class listener implements MediaPlayer.OnCompletionListener {
public void onCompletion(MediaPlayer mp) {
waitingForPlayer = false;
long timeInMilli = Calendar.getInstance().getTime().getTime();
long timeToQuit = (1000 * 30) + timeInMilli; // add 30 seconds
if (mp1playing)
{
mp1.reset();
removefile();
mp1prepared = false;
// Log.d(TAG, "mp1 is Free.");
if (downloadingformp2) {
if (mp2preparing && stopping == false) {
waitingForPlayer = true;
}
while (mp2preparing && stopping == false) {
if (timeInMilli > timeToQuit) {
stopSelf();
}
timeInMilli = Calendar.getInstance().getTime().getTime();
}
}
} else {
mp2.reset();
removefile();
mp2prepared = false;
if (downloadingformp1) {
if (mp1preparing && stopping == false) {
waitingForPlayer = true;
}
while (mp1preparing && stopping == false) {
if (timeInMilli > timeToQuit) {
stopSelf();
}
timeInMilli = Calendar.getInstance().getTime().getTime();
}
}
}
if (waitingForPlayer == true) {
// we must have been waiting
waitingForPlayer = false;
}
if (stopping == false) {
if (mp1playing) {
mp2.start();
mp1playing = false;
Runnable r = new Runnable() {
public void run() {
setupplayer();
}
};
Thread t = new Thread(r);
t.start();
} else {
mp1.start();
mp1playing = true;
Runnable r = new Runnable() {
public void run() {
setupplayer();
}
};
Thread t = new Thread(r);
t.start();
}
}
}
}
/** OnPreparedListener for media player **/
class preparelistener implements MediaPlayer.OnPreparedListener {
public void onPrepared(MediaPlayer mp) {
if (prepareState) {
prepareState = false;
mp1preparing = false;
mp1prepared = true;
if (started == false) {
started = true;
mp1.start();
mp1playing = true;
Runnable r = new Runnable() {
public void run() {
setupplayer();
}
};
Thread t = new Thread(r);
t.start();
}
} else {
prepareState = true;
mp2preparing = false;
mp2prepared = true;
}
}
};
/**
* Set Up player(s)
*/
public void setupplayer() {
final String TAG = "setupplayer";
Runnable r = new Runnable() {
public void run() {
try {
if (!mp1preparing && !mp1prepared) {
while (true) {
downloadingformp1 = true;
if (started == false)
break;
if (counter > preparecounter)
break;
}
File f = new File(context.getCacheDir(), DOWNFILE+ preparecounter);
FileInputStream ins = new FileInputStream(f);
mp1.setDataSource(ins.getFD());
mp1.setAudioStreamType(AudioManager.STREAM_MUSIC);//playing for live streaming
mp1.setOnCompletionListener(new listener());
mp1.setOnPreparedListener(new preparelistener());
if (started == false || waitingForPlayer == true){
}
mp1.prepareAsync();// .prepare();
mp1preparing = true;
downloadingformp1 = false;
preparecounter++;
} else if (!mp2preparing && !mp2prepared) {
while (true) {
downloadingformp2 = true;
if (started == false)
break;
if (counter > preparecounter)
break;
}
File f = new File(context.getCacheDir(), DOWNFILE+ preparecounter);
FileInputStream ins = new FileInputStream(f);
mp2.setDataSource(ins.getFD());
mp2.setAudioStreamType(AudioManager.STREAM_MUSIC);
mp2.setOnCompletionListener(new listener());
mp2.setOnPreparedListener(new preparelistener());
mp2.prepareAsync();
mp2preparing = true;
downloadingformp2 = false;
preparecounter++;
// }
} else
Log.d(TAG, "No Media player is available to setup.");
return;
} catch (FileNotFoundException e) {
Log.e(TAG, e.toString());
Log.e(TAG,"Can't find file. Android must have deleted it on a clean up ");
stop();
return;
} catch (IllegalStateException e) {
Log.e(TAG, e.toString());
stop();
} catch (IOException e) {
Log.e(TAG, e.toString());
stop();
}
}
};
preparringthread = new Thread(r);
preparringthread.start();
try {
preparringthread.join();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
private void removefile() {
File temp = new File(context.getCacheDir(), DOWNFILE + playedcounter);
temp.delete();
playedcounter++;
}
public boolean stop() {
final String TAG = "STOP";
stopping = true;
try {
if (mp1.isPlaying()){
if (!(stream == null)) {
Log.i("IN STOP", "MP1 is nill");
stopSelf();
}
mp1.stop();
}
if (mp2.isPlaying()){
Log.i("IN STOP", "MP2 is nill");
if (!(stream == null)){
stopSelf();
}
mp2.stop();
}
} catch (Exception e) {
Log.e(TAG, "error stopping players");
}
if (stream != null) {
try {
stream.close();
} catch (IOException e) {
Log.e(TAG, "error closing open connection");
}
}
stream = null;
processHasStarted = false;
processHasPaused = true;
if (preparringthread != null) {
preparringthread.interrupt();
}
stopSelf();
return true;
}
public boolean isPlaying() {
return processHasStarted;
}
public boolean isPause() {
return processHasPaused;
}
private void raiseThreadPriority() {
Process.setThreadPriority(Process.THREAD_PRIORITY_AUDIO);
}
}
you should call release(), to free the resources. If not released, too many MediaPlayer instances may result in an exception
Write this code when on youe Service
Updated
private void releaseMediaPlayer() {
if (mediaPlayer != null) {
if(mediaPlayer.isPlaying()) {
mediaPlayer.stop();
}
mediaPlayer.release();
mediaPlayer = null;
}
}
#Override
protected void onDestroy() {
super.onDestroy();
releaseMediaPlayer();
}
You can see this

Using Android USB Host API to read my USB game controller/Or other USB device data

I am trying to use Android USB Host API to read my USB game controller data, once I get this to work, I will connect other device to test.
My game controller is connected to my Android phone using OTG cable. I am now able to get device, endpoints information, but I don't know how to read the raw data and display it.
Can someone please help me? Some example codes will be appreciated.
TextView countDisplay;
ArrayList<String> listItems = new ArrayList<String>();
ArrayAdapter<String> adapter;
String values = "";
UsbManager mManager;
UsbDevice device = null;
private byte[] bytes;
private static int TIMEOUT = 0;
private boolean forceClaim = true;
static PendingIntent mPermissionIntent;
UsbDeviceConnection connection = null;
UsbEndpoint InputEndpoint = null;
UsbEndpoint OutputEndpoint = null;
private Handler mHandler = new Handler();
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
mManager = (UsbManager) getSystemService(Context.USB_SERVICE);
mPermissionIntent = PendingIntent.getBroadcast(this, 0, new Intent(
"com.android.example.USB_PERMISSION"), 0);
IntentFilter filter = new IntentFilter();
filter.addAction(UsbManager.ACTION_USB_DEVICE_ATTACHED);
filter.addAction(UsbManager.ACTION_USB_DEVICE_DETACHED);
registerReceiver(mUsbReceiver, filter);
HashMap<String, UsbDevice> deviceList = mManager.getDeviceList();
values = values + "deviceListSize:" + deviceList.size() + ",tostring:"
+ deviceList.toString();
Iterator<UsbDevice> deviceIterator = deviceList.values().iterator();
while (deviceIterator.hasNext()) {
device = deviceIterator.next();
values = values + ",device id:" + device.getDeviceId()
+ ",device name:" + device.getDeviceName();
values = values + ",Protocol:" + device.getDeviceProtocol()
+ ",ProductId:" + device.getProductId();
values = values + ",DeviceClass:" + device.getDeviceClass()
+ ",VendorId:" + device.getVendorId();
}
if (device != null) {
values = values + ",getInterfaceCount:"
+ device.getInterfaceCount();
UsbInterface intf = device.getInterface(0);
values = values + ",intf.getEndpointCount():"
+ intf.getEndpointCount();
UsbEndpoint endpoint1 = intf.getEndpoint(0);
UsbEndpoint endpoint2 = intf.getEndpoint(1);
mManager.requestPermission(device, mPermissionIntent);
if (mManager.hasPermission(device)) {
values = values + ",has permission over device!";
connection = mManager.openDevice(device);
if (connection == null) {
values = values + ",connection null";
} else {
values = values + ",getFileDescriptor:"
+ connection.getFileDescriptor();
if (endpoint1.getDirection() == UsbConstants.USB_DIR_IN) {
InputEndpoint = endpoint1;
} else {
OutputEndpoint = endpoint1;
}
if (endpoint2.getDirection() == UsbConstants.USB_DIR_IN) {
InputEndpoint = endpoint2;
} else {
OutputEndpoint = endpoint2;
}
}
if (InputEndpoint == null) {
countDisplay.setText(values + ",InputEndpoint is null");
}
if (OutputEndpoint == null) {
countDisplay.setText(values + ",OutputEndPoint is null");
}
connection.claimInterface(intf, forceClaim);
mHandler.postDelayed(runnable, 1);
} else {
values = values + ",Do not have permission over device!";
}
}
setContentView(R.layout.activity_main);
LayoutInflater inflater = (LayoutInflater) getSystemService(Context.LAYOUT_INFLATER_SERVICE);
View v = inflater.inflate(R.layout.activity_main, null);
LinearLayout ll = new LinearLayout(this);
ll.setOrientation(LinearLayout.VERTICAL);
int counter = 1;
countDisplay = new TextView(this);
ll.addView(countDisplay);
countDisplay.setText(values + ",counter here");
final Button button = new Button(this);
button.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View v) {
// TODO Auto-generated method stub
if (device != null && mManager.hasPermission(device)) {
values = values + ",device id:" + device.getDeviceId()
+ ",device name:" + device.getDeviceName();
values = values + ",Protocol:" + device.getDeviceProtocol()
+ ",ProductId:" + device.getProductId();
values = values + ",DeviceClass:" + device.getDeviceClass()
+ ",VendorId:" + device.getVendorId();
countDisplay.setText(values + ",okok");
} else {
if (device != null)
mManager.requestPermission(device, mPermissionIntent);
}
}
});
ll.addView(button);
setContentView(ll);
}
And Runnable:
private Runnable runnable = new Runnable() {
public void run() {
if (connection != null) {
int count = connection.bulkTransfer(InputEndpoint, bytes,
bytes.length, TIMEOUT);
countDisplay.setText(values + ",bultTransferNo:" + count);
countDisplay.setText(values + "bulkValue:" + bytes);
} else {
countDisplay.setText(values + ",connection is null");
}
}
};
This program serves as an example of the following USB host features:
Matching devices based on interface class, subclass and protocol (see device_filter.xml)
Asynchronous IO on bulk endpoints
All code Copyright:
/*
* Copyright (C) 2011 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
AdbDevice
package com.android.adb;
import android.hardware.usb.UsbConstants;
import android.hardware.usb.UsbDeviceConnection;
import android.hardware.usb.UsbEndpoint;
import android.hardware.usb.UsbInterface;
import android.hardware.usb.UsbRequest;
import android.util.SparseArray;
import java.util.LinkedList;
/* This class represents a USB device that supports the adb protocol. */
public class AdbDevice {
private final AdbTestActivity mActivity;
private final UsbDeviceConnection mDeviceConnection;
private final UsbEndpoint mEndpointOut;
private final UsbEndpoint mEndpointIn;
private String mSerial;
// pool of requests for the OUT endpoint
private final LinkedList<UsbRequest> mOutRequestPool = new LinkedList<UsbRequest>();
// pool of requests for the IN endpoint
private final LinkedList<UsbRequest> mInRequestPool = new LinkedList<UsbRequest>();
// list of currently opened sockets
private final SparseArray<AdbSocket> mSockets = new SparseArray<AdbSocket>();
private int mNextSocketId = 1;
private final WaiterThread mWaiterThread = new WaiterThread();
public AdbDevice(AdbTestActivity activity, UsbDeviceConnection connection,
UsbInterface intf) {
mActivity = activity;
mDeviceConnection = connection;
mSerial = connection.getSerial();
UsbEndpoint epOut = null;
UsbEndpoint epIn = null;
// look for our bulk endpoints
for (int i = 0; i < intf.getEndpointCount(); i++) {
UsbEndpoint ep = intf.getEndpoint(i);
if (ep.getType() == UsbConstants.USB_ENDPOINT_XFER_BULK) {
if (ep.getDirection() == UsbConstants.USB_DIR_OUT) {
epOut = ep;
} else {
epIn = ep;
}
}
}
if (epOut == null || epIn == null) {
throw new IllegalArgumentException("not all endpoints found");
}
mEndpointOut = epOut;
mEndpointIn = epIn;
}
// return device serial number
public String getSerial() {
return mSerial;
}
// get an OUT request from our pool
public UsbRequest getOutRequest() {
synchronized(mOutRequestPool) {
if (mOutRequestPool.isEmpty()) {
UsbRequest request = new UsbRequest();
request.initialize(mDeviceConnection, mEndpointOut);
return request;
} else {
return mOutRequestPool.removeFirst();
}
}
}
// return an OUT request to the pool
public void releaseOutRequest(UsbRequest request) {
synchronized (mOutRequestPool) {
mOutRequestPool.add(request);
}
}
// get an IN request from the pool
public UsbRequest getInRequest() {
synchronized(mInRequestPool) {
if (mInRequestPool.isEmpty()) {
UsbRequest request = new UsbRequest();
request.initialize(mDeviceConnection, mEndpointIn);
return request;
} else {
return mInRequestPool.removeFirst();
}
}
}
public void start() {
mWaiterThread.start();
connect();
}
public AdbSocket openSocket(String destination) {
AdbSocket socket;
synchronized (mSockets) {
int id = mNextSocketId++;
socket = new AdbSocket(this, id);
mSockets.put(id, socket);
}
if (socket.open(destination)) {
return socket;
} else {
return null;
}
}
private AdbSocket getSocket(int id) {
synchronized (mSockets) {
return mSockets.get(id);
}
}
public void socketClosed(AdbSocket socket) {
synchronized (mSockets) {
mSockets.remove(socket.getId());
}
}
// send a connect command
private void connect() {
AdbMessage message = new AdbMessage();
message.set(AdbMessage.A_CNXN, AdbMessage.A_VERSION, AdbMessage.MAX_PAYLOAD, "host::\0");
message.write(this);
}
// handle connect response
private void handleConnect(AdbMessage message) {
if (message.getDataString().startsWith("device:")) {
log("connected");
mActivity.deviceOnline(this);
}
}
public void stop() {
synchronized (mWaiterThread) {
mWaiterThread.mStop = true;
}
}
// dispatch a message from the device
void dispatchMessage(AdbMessage message) {
int command = message.getCommand();
switch (command) {
case AdbMessage.A_SYNC:
log("got A_SYNC");
break;
case AdbMessage.A_CNXN:
handleConnect(message);
break;
case AdbMessage.A_OPEN:
case AdbMessage.A_OKAY:
case AdbMessage.A_CLSE:
case AdbMessage.A_WRTE:
AdbSocket socket = getSocket(message.getArg1());
if (socket == null) {
log("ERROR socket not found");
} else {
socket.handleMessage(message);
}
break;
}
}
void log(String s) {
mActivity.log(s);
}
private class WaiterThread extends Thread {
public boolean mStop;
public void run() {
// start out with a command read
AdbMessage currentCommand = new AdbMessage();
AdbMessage currentData = null;
// FIXME error checking
currentCommand.readCommand(getInRequest());
while (true) {
synchronized (this) {
if (mStop) {
return;
}
}
UsbRequest request = mDeviceConnection.requestWait();
if (request == null) {
break;
}
AdbMessage message = (AdbMessage)request.getClientData();
request.setClientData(null);
AdbMessage messageToDispatch = null;
if (message == currentCommand) {
int dataLength = message.getDataLength();
// read data if length > 0
if (dataLength > 0) {
message.readData(getInRequest(), dataLength);
currentData = message;
} else {
messageToDispatch = message;
}
currentCommand = null;
} else if (message == currentData) {
messageToDispatch = message;
currentData = null;
}
if (messageToDispatch != null) {
// queue another read first
currentCommand = new AdbMessage();
currentCommand.readCommand(getInRequest());
// then dispatch the current message
dispatchMessage(messageToDispatch);
}
// put request back into the appropriate pool
if (request.getEndpoint() == mEndpointOut) {
releaseOutRequest(request);
} else {
synchronized (mInRequestPool) {
mInRequestPool.add(request);
}
}
}
}
}
}
AdbMessage
package com.android.adb;
import android.hardware.usb.UsbRequest;
import java.nio.ByteBuffer;
import java.nio.ByteOrder;
/* This class encapsulates and adb command packet */
public class AdbMessage {
// command names
public static final int A_SYNC = 0x434e5953;
public static final int A_CNXN = 0x4e584e43;
public static final int A_OPEN = 0x4e45504f;
public static final int A_OKAY = 0x59414b4f;
public static final int A_CLSE = 0x45534c43;
public static final int A_WRTE = 0x45545257;
// ADB protocol version
public static final int A_VERSION = 0x01000000;
public static final int MAX_PAYLOAD = 4096;
private final ByteBuffer mMessageBuffer;
private final ByteBuffer mDataBuffer;
public AdbMessage() {
mMessageBuffer = ByteBuffer.allocate(24);
mDataBuffer = ByteBuffer.allocate(MAX_PAYLOAD);
mMessageBuffer.order(ByteOrder.LITTLE_ENDIAN);
mDataBuffer.order(ByteOrder.LITTLE_ENDIAN);
}
// sets the fields in the command header
public void set(int command, int arg0, int arg1, byte[] data) {
mMessageBuffer.putInt(0, command);
mMessageBuffer.putInt(4, arg0);
mMessageBuffer.putInt(8, arg1);
mMessageBuffer.putInt(12, (data == null ? 0 : data.length));
mMessageBuffer.putInt(16, (data == null ? 0 : checksum(data)));
mMessageBuffer.putInt(20, command ^ 0xFFFFFFFF);
if (data != null) {
mDataBuffer.put(data, 0, data.length);
}
}
public void set(int command, int arg0, int arg1) {
set(command, arg0, arg1, (byte[])null);
}
public void set(int command, int arg0, int arg1, String data) {
// add trailing zero
data += "\0";
set(command, arg0, arg1, data.getBytes());
}
// returns the command's message ID
public int getCommand() {
return mMessageBuffer.getInt(0);
}
// returns command's first argument
public int getArg0() {
return mMessageBuffer.getInt(4);
}
// returns command's second argument
public int getArg1() {
return mMessageBuffer.getInt(8);
}
// returns command's data buffer
public ByteBuffer getData() {
return mDataBuffer;
}
// returns command's data length
public int getDataLength() {
return mMessageBuffer.getInt(12);
}
// returns command's data as a string
public String getDataString() {
int length = getDataLength();
if (length == 0) return null;
// trim trailing zero
return new String(mDataBuffer.array(), 0, length - 1);
}
public boolean write(AdbDevice device) {
synchronized (device) {
UsbRequest request = device.getOutRequest();
request.setClientData(this);
if (request.queue(mMessageBuffer, 24)) {
int length = getDataLength();
if (length > 0) {
request = device.getOutRequest();
request.setClientData(this);
if (request.queue(mDataBuffer, length)) {
return true;
} else {
device.releaseOutRequest(request);
return false;
}
}
return true;
} else {
device.releaseOutRequest(request);
return false;
}
}
}
public boolean readCommand(UsbRequest request) {
request.setClientData(this);
return request.queue(mMessageBuffer, 24);
}
public boolean readData(UsbRequest request, int length) {
request.setClientData(this);
return request.queue(mDataBuffer, length);
}
private static String extractString(ByteBuffer buffer, int offset, int length) {
byte[] bytes = new byte[length];
for (int i = 0; i < length; i++) {
bytes[i] = buffer.get(offset++);
}
return new String(bytes);
}
#Override
public String toString() {
String commandName = extractString(mMessageBuffer, 0, 4);
int dataLength = getDataLength();
String result = "Adb Message: " + commandName + " arg0: " + getArg0() +
" arg1: " + getArg1() + " dataLength: " + dataLength;
if (dataLength > 0) {
result += (" data: \"" + getDataString() + "\"");
}
return result;
}
private static int checksum(byte[] data) {
int result = 0;
for (int i = 0; i < data.length; i++) {
int x = data[i];
// dang, no unsigned ints in java
if (x < 0) x += 256;
result += x;
}
return result;
}
}
AdbSocket
package com.android.adb;
/* This class represents an adb socket. adb supports multiple independent
* socket connections to a single device. Typically a socket is created
* for each adb command that is executed.
*/
public class AdbSocket {
private final AdbDevice mDevice;
private final int mId;
private int mPeerId;
public AdbSocket(AdbDevice device, int id) {
mDevice = device;
mId = id;
}
public int getId() {
return mId;
}
public boolean open(String destination) {
AdbMessage message = new AdbMessage();
message.set(AdbMessage.A_OPEN, mId, 0, destination);
if (! message.write(mDevice)) {
return false;
}
synchronized (this) {
try {
wait();
} catch (InterruptedException e) {
return false;
}
}
return true;
}
public void handleMessage(AdbMessage message) {
switch (message.getCommand()) {
case AdbMessage.A_OKAY:
mPeerId = message.getArg0();
synchronized (this) {
notify();
}
break;
case AdbMessage.A_WRTE:
mDevice.log(message.getDataString());
sendReady();
break;
}
}
private void sendReady() {
AdbMessage message = new AdbMessage();
message.set(AdbMessage.A_OKAY, mId, mPeerId);
message.write(mDevice);
}
}
For additional information on usb and connecting you might find the following article helpfull.
http://android.serverbox.ch/?p=549
The last paragraph explains some of the issue you might face. The example they provide may also show you how to go about reading the data and how you will have to format the messages.
It looks like you face two issue. One setting up your code to read message, which Puspendu's answer aludes to, and the second issue which is "how" to communicate, what messages you will need to send to establish a connection, handshake, and determine the good stuff, i.e. the data you want.
Puspendu has shown one example of reading and writing to a device. However i would imagine that depending on the device you connect, the handshake and message structure will change, hence you'll have to look those parts up (afraid i dont know of any other examples).

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