我尝试从我的评估板中读取数据。它是Stellaris EKK-LM4F232 Evalutaion Kit。它有五个按钮。我按下一个按钮并将数据发送到我的Android设备。例如，我按一次，然后发送到1，第二次发送到2 ....当我第一次按下按钮时，我从Android设备收到第一个值（它意味着1）。但是当我再次按下按钮时，我无法接收任何其他值，如2,3,4，.... 这是我的阅读代码。它在启动时连续读取。你能救我吗？
public void startDataRecieve() {
new Thread(new Runnable() {
@Override
public void run() {
UsbEndpoint endpoint = null;
for (int i = 0; i < intf.getEndpointCount(); i++) {
if (intf.getEndpoint(i).getDirection() == UsbConstants.USB_DIR_IN) {
endpoint = intf.getEndpoint(i);
break;
}
}
UsbRequest request = new UsbRequest(); // create an URB
boolean initilzed = request.initialize(connection, endpoint);
if (!initilzed) {
Log.e("USB CONNECTION FAILED", "Request initialization failed for reading");
return;
}
while (true) {
int bufferMaxLength = endpoint.getMaxPacketSize();
ByteBuffer buffer = ByteBuffer.allocate(bufferMaxLength);
if (request.queue(buffer, bufferMaxLength) == true) {
if (connection.requestWait() == request) {
String result = new String(buffer.array());
Log.i("GELEN DATA : ", result);
listener.readData(result);
}
}
}
}
}).start();
}
如果你不能很好地理解，那么一个人就会问同一个问题 Android bulkTransfer return -1 when read data but there is really some data in the buffer
与@Mike Ortiz讨论后，我把所有代码放在这里。当我点击按钮发送android设备发送“START”命令到设备然后读取开始。 当我发送到Android设备的第一个值，我可以得到它，但在第一个值后，我没有从USB设备获得任何价值。我确信usb设备会发送值。
public class MainActivity extends Activity implements Runnable {
private static final String TAG = "MAIN ACTIVITY TEST ";
private Button buttonConnect;
private Button butonSend;
private Button buttonDisconnect;
private TextView textViewResult;
private UsbDevice device;
private Thread readThread;
private UsbManager usbManager;
private UsbDeviceConnection connection;
private UsbInterface usbInterface;
private UsbEndpoint usbEndpointIn;
private UsbEndpoint usbEndpointOut;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
initView();
PendingIntent mPermissionIntent = PendingIntent.getBroadcast(this, 0, new Intent(ACTION_USB_PERMISSION), 0);
IntentFilter filter = new IntentFilter(ACTION_USB_PERMISSION);
registerReceiver(usbReceiver, filter);
usbManager = (UsbManager) getSystemService(Context.USB_SERVICE);
HashMap<String, UsbDevice> deviceList = usbManager.getDeviceList();
Iterator<UsbDevice> deviceIterator = deviceList.values().iterator();
while (deviceIterator.hasNext()) {
UsbDevice device = deviceIterator.next();
if (device.getVendorId() == 7358 && device.getProductId() == 3) {
this.device = device;
usbManager.requestPermission(device, mPermissionIntent);
break;
}
}
butonSend.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
usbInterface = device.getInterface(0);
connection = usbManager.openDevice(device);
connection.claimInterface(usbInterface, false);
for (int i = 0; i < usbInterface.getEndpointCount(); i++) {
UsbEndpoint end = usbInterface.getEndpoint(i);
if (end.getDirection() == UsbConstants.USB_DIR_IN) {
usbEndpointIn = end;
} else {
usbEndpointOut = end;
}
}
//SEND START COMMAND TO THE USB DEVICE;
int result = connection.bulkTransfer(usbEndpointOut, "START".getBytes(), "START".getBytes().length, 1000);
Log.e("SEND RESULT", result + "");
//START READING in run method
readThread = new Thread(MainActivity.this);
readThread.start();
}
});
buttonDisconnect.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
mRunning = false;
//readThread.stop();
connection.releaseInterface(usbInterface);
connection.close();
Log.e(TAG, "Connection CLosed.");
}
});
}
private static final String ACTION_USB_PERMISSION = "com.android.example.USB_PERMISSION";
private final BroadcastReceiver usbReceiver = 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) {
Toast.makeText(MainActivity.this, "Cihaza izin verildi", Toast.LENGTH_LONG).show();
}
} else {
Toast.makeText(MainActivity.this, "Cihaza izin verilmedi.", Toast.LENGTH_LONG).show();
Log.d(TAG, "permission denied for device " + device);
}
}
}
}
};
private boolean mRunning;
private void initView() {
butonSend = (Button) findViewById(R.id.buttonSend);
buttonConnect = (Button) findViewById(R.id.buttonConnect);
textViewResult = (TextView) findViewById(R.id.textViewResult);
buttonDisconnect = (Button) findViewById(R.id.buttonDisconnect);
}
@Override
public void run() {
mRunning = true;
//READ VALUE UNTIL DISCONNECT
while (mRunning) {
byte[] bytes = new byte[usbEndpointIn.getMaxPacketSize()];
int result = connection.bulkTransfer(usbEndpointIn, bytes, bytes.length, 1000);
if(result > 0)
Log.e("RESULT : " + result, " VALUE : " + new String(bytes));
}
Log.d("Thread", "STOPPPED");
}
}
答案 0 :(得分：4)
你的循环中哪个条件失败了？ (request.queue(buffer, bufferMaxLength) == true)或(connection.requestWait() == request)？如果是第二个，我建议您使用.equals()代替参考比较==。
您是否尝试过使用批量转移而不是请求？
private UsbManager mManager;
private UsbDevice mDevice;
private UsbDeviceConnection mDeviceConnection;
private UsbInterface mInterface;
private UsbEndpoint mEndpointIn;
public void run() {
while (mEndpointIn != null && mDeviceConnection != null) {
byte[] recordIn = new byte[mEndpointIn.getMaxPacketSize()];
int receivedLength = mDeviceConnection.bulkTransfer(mEndpointIn, recordIn,
recordIn.length, mTimeout);
if (receivedLength > -1) passDataToListener(recordIn);
}
}
public void initializeCommunication(Context context) throws UsbDeviceException {
mInterface = findHidInterface();
if (mManager != null && mDevice != null && mInterface != null) {
mDeviceConnection = mManager.openDevice(mDevice);
if (mDeviceConnection != null) {
if (mDeviceConnection.claimInterface(mInterface, true)) {
UsbEndpoint usbEndpointOut = null;
UsbEndpoint usbEndpointIn = null;
//
// Look for Interrupt endpoints
//
for (int i = 0; i < mInterface.getEndpointCount(); i++) {
UsbEndpoint usbEndpoint = mInterface.getEndpoint(i);
if (usbEndpoint.getType() == UsbConstants.USB_ENDPOINT_XFER_INT) {
if (usbEndpoint.getDirection() == UsbConstants.USB_DIR_OUT) {
usbEndpointOut = usbEndpoint;
} else {
usbEndpointIn = usbEndpoint;
}
}
}
if (usbEndpointOut == null || usbEndpointIn == null) {
Log.w(DEBUG, "No USB endpoints found.");
}
mEndpointOut = usbEndpointOut;
mEndpointIn = usbEndpointIn;
} else {
mDeviceConnection.close();
Log.w(DEBUG, "USB claim interface failed.");
}
} else {
Log.w(DEBUG, "USB open device failed.");
}
} else {
Log.w(DEBUG, "Some essential USB variables were null.");
}
}
/**
* Find the HID interface.
*
* @return
* Return the HID interface if found, otherwise null.
*/
private UsbInterface findHidInterface() {
if (mDevice != null) {
final int interfaceCount = mDevice.getInterfaceCount();
for (int interfaceIndex = 0; interfaceIndex < interfaceCount; interfaceIndex++) {
UsbInterface usbInterface = mDevice.getInterface(interfaceIndex);
//
// Can add UsbInterface.getInterfaceSubclass() and
// UsbInterface.getInterfaceProtocol() for more specifics.
//
if (usbInterface.getInterfaceClass() == UsbConstants.USB_CLASS_HID) {
return usbInterface;
}
}
Log.w(DEBUG, "HID interface not found.");
}
return null;
}