Reading from Barcode reader with CdcAcmSerialDriver returns zeros

[vladaman]

I am trying to read data from Barcode, which is set to CDC Mode. Tested on Linux with cat /dev/ttyACM0 which it gives me proper output. Android code:

ProbeTable customTable = new ProbeTable();
customTable.addProduct(0x0525, 0xa4a7, CdcAcmSerialDriver.class);
customTable.addProduct(0x1eab, 0x1D06, CdcAcmSerialDriver.class); 
UsbSerialProber prober = new UsbSerialProber(customTable);
List<UsbSerialDriver> availableDrivers = prober.findAllDrivers(manager);

UsbSerialDriver driver = availableDrivers.get(0);
UsbDeviceConnection connection = manager.openDevice(driver.getDevice());
UsbSerialPort usbSerialPort = driver.getPorts().get(0);
usbSerialPort.open(connection);
usbSerialPort.setParameters(9600, 8, UsbSerialPort.STOPBITS_1, UsbSerialPort.PARITY_NONE); // whatever speed I set I get zeros bellow

byte[] response = new byte[6];
while (!Thread.interrupted() && active) {
  int len = usbSerialPort.read(response, READ_WAIT_MILLIS);
  // response byte content is 0x000000000000
}

 Available driver device=UsbDevice[mName=/dev/bus/usb/001/007,mVendorId=7851,mProductId=7430,mClass=2,mSubclass=0,mProtocol=0,mManufacturerName=Newland Auto-ID,mProductName=NLS-FM430MD-SR-U USB CDC,mVersion=0.01,mSerialNumberReader=android.hardware.usb.IUsbSerialReader$Stub$Proxy@43902ce, mHasAudioPlayback=false, mHasAudioCapture=false, mHasMidi=false, mHasVideoCapture=false, mHasVideoPlayback=false, mConfigurations=[
    UsbConfiguration[mId=1,mName=USB CDC mode,mAttributes=128,mMaxPower=250,mInterfaces=[
    UsbInterface[mId=0,mAlternateSetting=0,mName=CDC ACM Comm,mClass=2,mSubclass=2,mProtocol=1,mEndpoints=[
UsbEndpoint[mAddress=131,mAttributes=3,mMaxPacketSize=16,mInterval=8]]
      UsbInterface[mId=1,mAlternateSetting=0,mName=CDC ACM Data,mClass=10,mSubclass=0,mProtocol=0,mEndpoints=[
UsbEndpoint[mAddress=129,mAttributes=2,mMaxPacketSize=64,mInterval=0]
UsbEndpoint[mAddress=2,mAttributes=2,mMaxPacketSize=64,mInterval=0]]]] ports=[<CdcAcmSerialPort device_name=/dev/bus/usb/001/007 device_id=1007 port_number=0>]

It always reads zeros, regardless of setRTS/setDTR/setParameters values.

[kai-morich]

please try with a larger read buffer as explained here