1. 检查系统是否开启了usb host功能

  确认/system/etc/permissions目录有android.hardware.usb.host.xml这个文件。

2. 查找设备

在AndroidManifest.xml中添加：
<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" />

res/xml/device_filter.xml的内容如下，注意为10进制数

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <usb-device vendor-id="1234" product-id="5678" class="255" subclass="66" protocol="1" />
</resources>

方法1

在<activity ...></activity>之间加intent-filter之间，这样当USB设备插入时会启动这个Activity，通过
UsbDevice device = (UsbDevice) intent.getParcelableExtra(UsbManager.EXTRA_DEVICE);获取设备

方法2

不用系统的广播的话，可以遍历设备列表，得到设备

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()
    //查找想要的设备
    if (device.getVenderId()==venderID && device.getProductId==productId)
        //your code
}

通过UsbManager的requestPermission方法申请usb权限 manager.requestPermission(device, null);会弹出选择框让用户选择是否允许应用访问usb设备。

3. 通信

官网例子

private Byte[] bytes
private static int TIMEOUT = 0;
private boolean forceClaim = true;
...
UsbInterface intf = device.getInterface(0);
UsbEndpoint endpoint = intf.getEndpoint(0);
UsbDeviceConnection connection = mUsbManager.openDevice(device); 
connection.claimInterface(intf, forceClaim);
connection.bulkTransfer(endpoint, bytes, bytes.length, TIMEOUT); //do in another thread

获取usb设备端点

  UsbEndpoint ep = intf.getEndpoint(i);
  ep.getType() == UsbConstants.USB_ENDPOINT_XFER_INT;//中断
  ep.getDirection()==UsbConstants.USB_DIR_OUT;//相对主机来说

使用UsbRequest

发送

ByteBuffer mOutData = ByteBuffer.allocate(len);
UsbRequest mUsbRequest = new UsbRequest();
mUsbRequest.initialize(connection, mEndpointOut);
mUsbRequest.queue(mOutData, len);
if (connection.requestWait()==mUsbRequest)
    //成功

接收，不知道为什么在4.2上mInData要ByteBuffer.allocate(len*2)

//ByteBuffer mInData = ByteBuffer.allocate(len);//4.0
ByteBuffer mInData = ByteBuffer.allocate(len*2);
UsbRequest mUsbRequest = new UsbRequest();
mUsbRequest.initialize(connection, mEndpointIn);
mUsbRequest.queue(mInData, len);
if (connection.requestWait()==mUsbRequest)
    byte[] data = mInData.array();