Android – USB interface in android

Probably you will actually need to read the Raw USB Descriptors to get at the data you want. Here's a basic USB device discovery program I wrote for my own purposes. Mind you that I'm looking for a specific device (a Dajac Easy I/O 1000 data acquisition system) but you can apply the same principles. I do show you how to get the data you're looking for.

Here's the code first. My package is usbtest3, and the file is MainActivity.java:

package com.hotspotoffice.usbtest3;

// David Schofield, Hotspot Office, LLC., Pittsburgh, PA.
// Donations via PayPal always welcome! schofield (dot) david (at) verizon.net

import java.io.UnsupportedEncodingException;
import java.util.HashMap;
import java.util.Iterator;
import android.os.Bundle;
import android.app.Activity;
import android.app.PendingIntent;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.content.IntentFilter;
import android.view.View;
import android.view.Menu;
import android.widget.Button;
import android.widget.TextView;
import android.hardware.usb.UsbConstants;
import android.hardware.usb.UsbManager;
import android.hardware.usb.UsbDevice;
import android.hardware.usb.UsbDeviceConnection;
import android.hardware.usb.UsbInterface;


public class MainActivity extends Activity {

    protected static final int STD_USB_REQUEST_GET_DESCRIPTOR = 0x06;
    // http://libusb.sourceforge.net/api-1.0/group__desc.html
    protected static final int LIBUSB_DT_STRING = 0x03;
    private static final String ACTION_USB_PERMISSION = "com.android.example.USB_PERMISSION";

    private Button btnDiscover;
    private TextView txtInfo;
    private PendingIntent mPermissionIntent; 

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

        btnDiscover=(Button)findViewById(R.id.btnDiscover);
        txtInfo=(TextView)findViewById(R.id.txtInfo);

        mPermissionIntent = PendingIntent.getBroadcast(this, 0, new Intent(ACTION_USB_PERMISSION), 0);
        IntentFilter filter = new IntentFilter(ACTION_USB_PERMISSION);
        registerReceiver(mUsbReceiver, filter);

        btnDiscover.setOnClickListener(new View.OnClickListener() {

            @Override
            public void onClick(View v) {
                // txtInfo.setText("Button has been Pressed for "+(++i)+" Times.");

                UsbManager manager = (UsbManager)getSystemService(Context.USB_SERVICE);

                HashMap<String, UsbDevice> deviceList = manager.getDeviceList();
                Iterator<UsbDevice> deviceIterator = deviceList.values().iterator();
                while(deviceIterator.hasNext()){
                    UsbDevice device = deviceIterator.next();

                    manager.requestPermission(device, mPermissionIntent);

                    txtInfo.append("Model:" + device.getDeviceName() + "\n");  
                    txtInfo.append("DeviceID:" + device.getDeviceId() + "\n");
                    txtInfo.append("Vendor:" + device.getVendorId() + "\n");
                    txtInfo.append("Product:" + device.getProductId() + "\n");
                    txtInfo.append("Class:" + device.getDeviceClass() + "\n");
                    txtInfo.append("Subclass:" + device.getDeviceSubclass() + "\n");
                    txtInfo.append("Protocol:" + device.getDeviceProtocol() + "\n");

                    UsbInterface intf = device.getInterface(0);
                    int epc = 0;
                    epc = intf.getEndpointCount();
                    txtInfo.append("Endpoints:" + epc + "\n");

                    txtInfo.append("Permission:" + Boolean.toString(manager.hasPermission(device))  + "\n");

                    UsbDeviceConnection connection = manager.openDevice(device);
                    if(null==connection){
                        txtInfo.append("(unable to establish connection)\n");
                    } else {

                        // Claims exclusive access to a UsbInterface. 
                        // This must be done before sending or receiving data on 
                        // any UsbEndpoints belonging to the interface.
                        connection.claimInterface(intf, true);

                        // getRawDescriptors can be used to access descriptors 
                        // not supported directly via the higher level APIs, 
                        // like getting the manufacturer and product names.
                        // because it returns bytes, you can get a variety of
                        // different data types.
                        byte[] rawDescs = connection.getRawDescriptors();
                        String manufacturer = "", product = "";

                        try
                        {
                            byte[] buffer = new byte[255];
                            int idxMan = rawDescs[14];
                            int idxPrd = rawDescs[15];

                            int rdo = connection.controlTransfer(UsbConstants.USB_DIR_IN
                                    | UsbConstants.USB_TYPE_STANDARD, STD_USB_REQUEST_GET_DESCRIPTOR,
                                    (LIBUSB_DT_STRING << 8) | idxMan, 0, buffer, 0xFF, 0);
                            manufacturer = new String(buffer, 2, rdo - 2, "UTF-16LE");

                            rdo = connection.controlTransfer(UsbConstants.USB_DIR_IN
                                            | UsbConstants.USB_TYPE_STANDARD, STD_USB_REQUEST_GET_DESCRIPTOR,
                                    (LIBUSB_DT_STRING << 8) | idxPrd, 0, buffer, 0xFF, 0);
                            product = new String(buffer, 2, rdo - 2, "UTF-16LE");

                        } catch (UnsupportedEncodingException e)
                        {
                        e.printStackTrace();
                        }

                        txtInfo.append("Manufacturer:" + manufacturer + "\n");                      
                        txtInfo.append("Product:" + product + "\n");                        
                        txtInfo.append("Serial#:" + connection.getSerial() + "\n");                     
                    }

                    txtInfo.append("------------------------------------\n");                   
                }               

            }
        });

    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.activity_main, menu);
        return true;
    }

    private 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
                       }
                    } 
                    else {
                        txtInfo.append("permission denied for device " + device);
                    }
                }
            }
        }
    };

}

My manifest file containing the intents and requirements for the USB Host device support:

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.hotspotoffice.usbtest3"
    android:versionCode="1"
    android:versionName="1.0" >

    <uses-feature android:name="android.hardware.usb.host" />

    <uses-sdk
        android:minSdkVersion="15"
        android:targetSdkVersion="15" />

    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >

        <activity
            android:name="com.hotspotoffice.usbtest3.MainActivity"
            android:label="@string/app_name" >

            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>

            <intent-filter>
                <action android:name="android.hardware.usb.action.USB_DEVICE_ATTACHED" />
            </intent-filter>

            <meta-data android:name="android.hardware.usb.action.USB_DEVICE_ATTACHED"
                android:resource="@xml/device_filter" />

        </activity>
    </application>

</manifest>

Finally, you will need a device filter. This is located under \res\xml\device_filter.xml Note that I had to create the xml folder myself, under \res.

<?xml version="1.0" encoding="utf-8"?>

<resources>
    <usb-device vendor-id="7635" product-id="1" class="255" subclass="255" protocol="0" />
</resources>

Note that all the fields need to be in decimal, not hex. You'll need to substitute your own vendor, product, class and subclass values from your own device. You can use a program like "USB Host View" or "USB Device Info" to discover these values. (download them free from the Play Store.)

Finally, here's how I defined the user interface in Activity_Main.xml
You'll need at least the Discover button, and the TextMultiline for output. (Ignore the Init and On/Off buttons.)

BTW, I'm using a 10" Toshiba Thrive tablet, so YMMV.

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity" >

    <EditText
        android:id="@+id/txtInfo"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignLeft="@+id/btnDiscover"
        android:layout_alignRight="@+id/textView1"
        android:layout_centerVertical="true"
        android:ems="10"
        android:inputType="textMultiLine"
        android:maxLines="50"
        android:minLines="20"
        android:minWidth="400dp" >

        <requestFocus />
    </EditText>

    <TextView
        android:id="@+id/textView1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_above="@+id/btnToggleDIO"
        android:layout_marginLeft="192dp"
        android:layout_toRightOf="@+id/btnDiscover"
        android:text="@string/lblDIO"
        android:textAppearance="?android:attr/textAppearanceMedium" />

    <Button
        android:id="@+id/btnDiscover"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignBaseline="@+id/btnInit"
        android:layout_alignBottom="@+id/btnInit"
        android:layout_alignParentLeft="true"
        android:layout_marginLeft="73dp"
        android:text="@string/strDiscover" />

    <ToggleButton
        android:id="@+id/btnToggleDIO"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignBaseline="@+id/btnInit"
        android:layout_alignBottom="@+id/btnInit"
        android:layout_alignLeft="@+id/textView1"
        android:text="@string/strIOState" />

    <Button
        android:id="@+id/btnInit"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_above="@+id/txtInfo"
        android:layout_marginBottom="29dp"
        android:layout_marginLeft="48dp"
        android:layout_toRightOf="@+id/btnDiscover"
        android:text="@string/strInit" />

</RelativeLayout>

When I run my program and plug in my device, it asks for my permission to connect and I say "Ok". then I click Discover, and it tells me among other things that the manufacturer is "Dajac Inc." the product is "EIO1000" and the serial# is "0000004B".

I wish you good providence; you can give me credit but it's only by standing on the shoulders of others (with a lot of my own sweat) I've been able to see this far. Pass it forward! -David