Android USB下的Accessory模式

Android USB开发麻烦还是比较多的。

第一种：host模式

这种模式比较不错，由Android设备提供电源，然后与外部设备通信。举个例子来说：电脑连接USB设备，都是这个模式，非常常见的模式。

但是有一个万恶的问题，android接外部USB设备的时候，驱动怎么办？又有那款芯片敢说Android系统支持他们家的芯片，又有哪个厂家说不动android系统装上他们家的驱动，他们家的设备就可以在Android上使用，或许这点上Android很难超越windows。

造成想现状：想加外部设备，都要：重新自己做底层驱动程序--->编译系统--->刷机--->编写android程序--->接入硬件实现功能。

整个一套下来饭都吃好几顿了。还是希望以后android发展发展能向window一样支持多设备驱动吧。

第二种：Accessory模式

这个模式比较揪心，外部设备要供给电源，数据间通信：电脑---手机就是这种模式，手机作为Accessory设备，电脑供给它电源，同时进行数据通信。

恰巧我也是用了这种模式：

程序需要做的：

（1）添加Action BoardCast

private static final String ACTION_USB_PERMISSION ="com.ukey.USB_PERMISSION";

/***********************USB handling******************************************/usbmanager = (UsbManager) context.getSystemService(Context.USB_SERVICE);mPermissionIntent = PendingIntent.getBroadcast(context, 0, new Intent(ACTION_USB_PERMISSION), 0);IntentFilter filter = new IntentFilter(ACTION_USB_PERMISSION);filter.addAction(UsbManager.ACTION_USB_ACCESSORY_DETACHED);context.registerReceiver(mUsbReceiver, filter);inputstream = null;outputstream = null;

（2）编写对应的boradCaset信息

/***********USB broadcast receiver*******************************************/private final BroadcastReceiver mUsbReceiver = new BroadcastReceiver() {@Overridepublic void onReceive(Context context, Intent intent) {String action = intent.getAction();if (ACTION_USB_PERMISSION.equals(action)) {synchronized (this){UsbAccessory accessory = (UsbAccessory) intent.getParcelableExtra(UsbManager.EXTRA_ACCESSORY);if (intent.getBooleanExtra(UsbManager.EXTRA_PERMISSION_GRANTED, false)){Toast.makeText(global_context, "Allow USB Permission", Toast.LENGTH_SHORT).show();OpenAccessory(accessory);}else{Toast.makeText(global_context, "Deny USB Permission", Toast.LENGTH_SHORT).show();}mPermissionRequestPending = false;}} else if (UsbManager.ACTION_USB_ACCESSORY_DETACHED.equals(action)){DestroyAccessory(true);}else{Log.d("LED", "....");}}};

（3）又来一个比较麻烦的事

android每次使用Accessory的时候都会询问你是否允许设备访问，这会点击是或否的结果又（2）中代码

if (intent.getBooleanExtra(UsbManager.EXTRA_PERMISSION_GRANTED, false))

去获得，然后才能使用OpenAccessory功能。

public int OpenAccessory(){// Intent intent = getIntent();if (inputstream != null && outputstream != null) {return 1;}UsbAccessory[] accessories = usbmanager.getAccessoryList();if(accessories != null){Toast.makeText(global_context, "Accessory Attached", Toast.LENGTH_SHORT).show();}else{// return 2 for accessory detached casereturn 2;}UsbAccessory accessory = (accessories == null ? null : accessories[0]);if (accessory != null) {if( -1 == accessory.toString().indexOf(ManufacturerString)){Toast.makeText(global_context, "Manufacturer is not matched!", Toast.LENGTH_SHORT).show();return 1;}if( -1 == accessory.toString().indexOf(ModelString1) && -1 == accessory.toString().indexOf(ModelString2)){Toast.makeText(global_context, "Model is not matched!", Toast.LENGTH_SHORT).show();return 1;}if( -1 == accessory.toString().indexOf(VersionString)){Toast.makeText(global_context, "Version is not matched!", Toast.LENGTH_SHORT).show();return 1;}Toast.makeText(global_context, "Manufacturer, Model & Version are matched!", Toast.LENGTH_SHORT).show();if (usbmanager.hasPermission(accessory)) {OpenAccessory(accessory);}else{synchronized (mUsbReceiver) {if (!mPermissionRequestPending) {Toast.makeText(global_context, "Request USB Permission", Toast.LENGTH_SHORT).show();usbmanager.requestPermission(accessory,mPermissionIntent);mPermissionRequestPending = true;}}}}return 0;}

启动请求。

（4）openAccessory功能

/*destroy accessory*/public void DestroyAccessory(boolean bConfiged){if(true == bConfiged){READ_ENABLE = false;  // set false condition for handler_thread to exit waiting data loopwriteusbdata[0] = 0;  // send dummy data for instream.read goingSendPacket(1, writeusbdata);}else{SetConfig((int)9600,(byte)8,(byte)1,(byte)0,(byte)0);  // send default setting data for configtry{Thread.sleep(10);}catch(Exception e){}READ_ENABLE = false;  // set false condition for handler_thread to exit waiting data loopwriteusbdata[0] = 0;  // send dummy data for instream.read goingSendPacket(1, writeusbdata);}try{Thread.sleep(10);}catch(Exception e){}CloseAccessory();}/*********************helper routines*************************************************/public void OpenAccessory(UsbAccessory accessory){filedescriptor = usbmanager.openAccessory(accessory);if(filedescriptor != null){usbaccessory = accessory;FileDescriptor fd = filedescriptor.getFileDescriptor();inputstream = new FileInputStream(fd);outputstream = new FileOutputStream(fd);/*check if any of them are null*/if(inputstream == null || outputstream==null){return;}if(READ_ENABLE == false){READ_ENABLE = true;readThread = new read_thread(inputstream);readThread.start();}}SetConfig((int)9600,(byte)8,(byte)1,(byte)0,(byte)0);}public void CloseAccessory(){try{if(filedescriptor != null)filedescriptor.close();}catch (IOException e){}try {if(inputstream != null)inputstream.close();} catch(IOException e){}try {if(outputstream != null)outputstream.close();}catch(IOException e){}/*FIXME, add the notfication also to close the application*/filedescriptor = null;inputstream = null;outputstream = null;//System.exit(0);}

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