如何从 Android 上的 USB 设备读取数据？

Question

I have a device which I need to connect via usb to my android phone. I simply want to read some data this device is sending and present it on my app screen. I've tried some API's such https://github.com/felHR85/UsbSerial and https://github.com/mik3y/usb-serial-for-android where I found the code below

    public class MainActivity extends AppCompatActivity {

    private TextView data;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        data = findViewById(R.id.data);

        UsbManager manager = (UsbManager) getSystemService(Context.USB_SERVICE);
        List<UsbSerialDriver> availableDrivers = UsbSerialProber.getDefaultProber().findAllDrivers(manager);
        if (availableDrivers.isEmpty()) {
            return;
        }

// Open a connection to the first available driver.
        UsbSerialDriver driver = availableDrivers.get(0);
        UsbDeviceConnection connection = manager.openDevice(driver.getDevice());
        if (connection == null) {
            // You probably need to call UsbManager.requestPermission(driver.getDevice(), ..)
            return;
        }

// Read some data! Most have just one port (port 0).
        UsbSerialPort port = driver.getPorts().get(0);
        try {
            port.open(connection);
            port.setParameters(57600, 8, UsbSerialPort.STOPBITS_1, UsbSerialPort.PARITY_NONE);

            byte buffer[] = new byte[8];
            int numBytesRead = port.read(buffer, 1000);
            //Log.d(TAG, "Read " + numBytesRead + " bytes.");
            data.setText(numBytesRead);
        } catch (IOException e) {
            // Deal with error.
        } finally {
            try {
                port.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
}

It simply does not read anything at all, is there a simpler way to do that?

The device I'm trying to read from is an oximeter (Ut-100). I only need some data to show up on the screen, is there a simple way to simple return an array of bytes and handle it by myself? Thanks for any help

Answer 1

You can start with Android Developer documentation USB HOST MODE to understand how to communicate over USB.

You should start with the section USB host overview .

Answer 2

Typically the UsbManager.requestPermission(...) handling is missing.

Please look at the recently enhanced examples @ https://github.com/mik3y/usb-serial-for-android