USB accessory support library

This provides a mechanism for developing applications to work with
USB accessories in versions of android prior to the introduction
of the android.hardware.UsbManager APIs.

Applications should link against the com.google.android.usb library
to use this support.

Change-Id: I48ff80467fd9a6667aa84a758eca754132f546b9
Signed-off-by: Mike Lockwood <lockwood@android.com>

11 files changed, 724 insertions, 0 deletions

diff --git a/libs/usb/Android.mk b/libs/usb/Android.mk
new file mode 100644
index 0000000..d0ef6f0
--- /dev/null
+++ b/libs/usb/Android.mk
@@ -0,0 +1,27 @@
+#
+# Copyright (C) 2008 The Android Open Source Project
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+
+LOCAL_PATH := $(call my-dir)
+
+include $(CLEAR_VARS)
+
+LOCAL_SRC_FILES := $(call all-java-files-under,src)
+
+LOCAL_MODULE_TAGS := optional
+
+LOCAL_MODULE:= com.google.android.usb
+
+include $(BUILD_JAVA_LIBRARY)
diff --git a/libs/usb/src/com/google/android/usb/UsbAccessory.java b/libs/usb/src/com/google/android/usb/UsbAccessory.java
new file mode 100644
index 0000000..91095f3
--- /dev/null
+++ b/libs/usb/src/com/google/android/usb/UsbAccessory.java
@@ -0,0 +1,96 @@
+/*
+ * Copyright (C) 2011 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.google.android.usb;
+
+/**
+ * A class representing a USB accessory.
+ */
+public final class UsbAccessory {
+
+    private final String mManufacturer;
+    private final String mModel;
+    private final String mType;
+    private final String mVersion;
+
+    /* package */ UsbAccessory(android.hardware.UsbAccessory accessory) {
+        mManufacturer = accessory.getManufacturer();
+        mModel = accessory.getModel();
+        mType = accessory.getType();
+        mVersion = accessory.getVersion();
+    }
+
+    /**
+     * Returns the manufacturer of the accessory.
+     *
+     * @return the accessory manufacturer
+     */
+    public String getManufacturer() {
+        return mManufacturer;
+    }
+
+    /**
+     * Returns the model name of the accessory.
+     *
+     * @return the accessory model
+     */
+    public String getModel() {
+        return mModel;
+    }
+
+    /**
+     * Returns the type of the accessory.
+     *
+     * @return the accessory type
+     */
+    public String getType() {
+        return mType;
+    }
+
+    /**
+     * Returns the version of the accessory.
+     *
+     * @return the accessory version
+     */
+    public String getVersion() {
+        return mVersion;
+    }
+
+    private static boolean compare(String s1, String s2) {
+        if (s1 == null) return (s2 == null);
+        return s1.equals(s2);
+    }
+
+    @Override
+    public boolean equals(Object obj) {
+        if (obj instanceof UsbAccessory) {
+            UsbAccessory accessory = (UsbAccessory)obj;
+            return (compare(mManufacturer, accessory.getManufacturer()) &&
+                    compare(mModel, accessory.getModel()) &&
+                    compare(mType, accessory.getType()) &&
+                    compare(mVersion, accessory.getVersion()));
+        }
+        return false;
+    }
+
+    @Override
+    public String toString() {
+        return "UsbAccessory[mManufacturer=" + mManufacturer +
+                            ", mModel=" + mModel +
+                            ", mType=" + mType +
+                            ", mVersion=" + mVersion + "]";
+    }
+}
diff --git a/libs/usb/src/com/google/android/usb/UsbManager.java b/libs/usb/src/com/google/android/usb/UsbManager.java
new file mode 100644
index 0000000..1b9bff9
--- /dev/null
+++ b/libs/usb/src/com/google/android/usb/UsbManager.java
@@ -0,0 +1,127 @@
+/*
+ * Copyright (C) 2011 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+
+package com.google.android.usb;
+
+import android.content.Context;
+import android.content.Intent;
+import android.hardware.IUsbManager;
+import android.os.IBinder;
+import android.os.ParcelFileDescriptor;
+import android.os.RemoteException;
+import android.os.ServiceManager;
+import android.util.Log;
+
+/**
+ * This class allows you to access the state of USB, both in host and device mode.
+ *
+ * <p>You can obtain an instance of this class by calling {@link #getInstance}
+ *
+ */
+public class UsbManager {
+    private static final String TAG = "UsbManager";
+
+   /**
+     * Broadcast Action:  A broadcast for USB accessory attached event.
+     *
+     * This intent is sent when a USB accessory is attached.
+     * Call {@link #getAccessory(android.content.Intent)} to retrieve the
+     * {@link com.google.android.usb.UsbAccessory} for the attached accessory.
+     */
+    public static final String ACTION_USB_ACCESSORY_ATTACHED =
+            "android.hardware.action.USB_ACCESSORY_ATTACHED";
+
+   /**
+     * Broadcast Action:  A broadcast for USB accessory detached event.
+     *
+     * This intent is sent when a USB accessory is detached.
+     * Call {@link #getAccessory(android.content.Intent)} to retrieve the
+     * {@link com.google.android.usb.UsbAccessory} for the attached accessory that was detached.
+     */
+    public static final String ACTION_USB_ACCESSORY_DETACHED =
+            "android.hardware.action.USB_ACCESSORY_DETACHED";
+
+    private final IUsbManager mService;
+
+    private UsbManager(IUsbManager service) {
+        mService = service;
+    }
+
+    /**
+     * Returns a new instance of this class.
+     *
+     * @return UsbManager instance.
+     */
+    public static UsbManager getInstance() {
+        IBinder b = ServiceManager.getService(Context.USB_SERVICE);
+        return new UsbManager(IUsbManager.Stub.asInterface(b));
+    }
+
+    /**
+     * Returns the {@link com.google.android.usb.UsbAccessory} for
+     * a {@link #ACTION_USB_ACCESSORY_ATTACHED} or {@link #ACTION_USB_ACCESSORY_ATTACHED}
+     * broadcast Intent
+     *
+     * @return UsbAccessory for the broadcast.
+     */
+    public static UsbAccessory getAccessory(Intent intent) {
+        android.hardware.UsbAccessory accessory =
+            intent.getParcelableExtra(android.hardware.UsbManager.EXTRA_ACCESSORY);
+        if (accessory == null) {
+            return null;
+        } else {
+            return new UsbAccessory(accessory);
+        }
+    }
+
+    /**
+     * Returns a list of currently attached USB accessories.
+     * (in the current implementation there can be at most one)
+     *
+     * @return list of USB accessories, or null if none are attached.
+     */
+    public UsbAccessory[] getAccessoryList() {
+        try {
+            android.hardware.UsbAccessory accessory = mService.getCurrentAccessory();
+            if (accessory == null) {
+                return null;
+            } else {
+                return new UsbAccessory[] { new UsbAccessory(accessory) };
+            }
+        } catch (RemoteException e) {
+            Log.e(TAG, "RemoteException in getAccessoryList" , e);
+            return null;
+        }
+    }
+
+    /**
+     * Opens a file descriptor for reading and writing data to the USB accessory.
+     *
+     * @param accessory the USB accessory to open
+     * @return file descriptor, or null if the accessor could not be opened.
+     */
+    public ParcelFileDescriptor openAccessory(UsbAccessory accessory) {
+        try {
+            return mService.openAccessory(new android.hardware.UsbAccessory(
+                    accessory.getManufacturer(),accessory.getModel(),
+                    accessory.getType(), accessory.getVersion()));
+        } catch (RemoteException e) {
+            Log.e(TAG, "RemoteException in openAccessory" , e);
+            return null;
+        }
+    }
+}
diff --git a/libs/usb/tests/AccessoryChat/Android.mk b/libs/usb/tests/AccessoryChat/Android.mk
new file mode 100644
index 0000000..b854569
--- /dev/null
+++ b/libs/usb/tests/AccessoryChat/Android.mk
@@ -0,0 +1,15 @@
+LOCAL_PATH:= $(call my-dir)
+include $(CLEAR_VARS)
+
+LOCAL_MODULE_TAGS := tests
+
+LOCAL_SRC_FILES := $(call all-subdir-java-files)
+
+LOCAL_PACKAGE_NAME := AccessoryChatGB
+
+LOCAL_JAVA_LIBRARIES := com.google.android.usb
+
+# Force an old SDK version to make sure we aren't using newer UsbManager APIs
+LOCAL_SDK_VERSION := 8
+
+include $(BUILD_PACKAGE)
diff --git a/libs/usb/tests/AccessoryChat/AndroidManifest.xml b/libs/usb/tests/AccessoryChat/AndroidManifest.xml
new file mode 100644
index 0000000..b63999c
--- /dev/null
+++ b/libs/usb/tests/AccessoryChat/AndroidManifest.xml
@@ -0,0 +1,23 @@
+<manifest xmlns:android="http://schemas.android.com/apk/res/android"
+        package="com.google.android.accessorychat">
+
+    <application>
+        <uses-library android:name="com.google.android.usb" />
+
+        <activity android:name="AccessoryChat" android:label="Accessory Chat GB">
+            <intent-filter>
+                <action android:name="android.intent.action.MAIN" />
+                <category android:name="android.intent.category.DEFAULT" />
+                <category android:name="android.intent.category.LAUNCHER" />
+            </intent-filter>
+
+            <intent-filter>
+                <action android:name="android.hardware.action.USB_ACCESSORY_ATTACHED" />
+            </intent-filter>
+
+            <meta-data android:name="android.hardware.action.USB_ACCESSORY_ATTACHED"
+                android:resource="@xml/accessory_filter" />
+        </activity>
+    </application>
+    <uses-sdk android:minSdkVersion="8" />
+</manifest>
diff --git a/libs/usb/tests/AccessoryChat/README.txt b/libs/usb/tests/AccessoryChat/README.txt
new file mode 100644
index 0000000..d2ce11e
--- /dev/null
+++ b/libs/usb/tests/AccessoryChat/README.txt
@@ -0,0 +1,10 @@
+This is a test app for the USB accessory APIs.  It consists of two parts:
+
+AccessoryChat - A Java app with a chat-like UI that sends and receives strings
+                via the UsbAccessory class.
+
+accessorychat - A C command-line program that communicates with AccessoryChat.
+                This program behaves as if it were a USB accessory.
+                It builds both for the host (Linux PC) and as an android
+                command line program, which will work if run as root on an
+                android device with USB host support
diff --git a/libs/usb/tests/AccessoryChat/accessorychat/Android.mk b/libs/usb/tests/AccessoryChat/accessorychat/Android.mk
new file mode 100644
index 0000000..300224a
--- /dev/null
+++ b/libs/usb/tests/AccessoryChat/accessorychat/Android.mk
@@ -0,0 +1,34 @@
+LOCAL_PATH:= $(call my-dir)
+
+# Build for Linux (desktop) host
+ifeq ($(HOST_OS),linux)
+
+include $(CLEAR_VARS)
+
+LOCAL_MODULE_TAGS := optional
+
+LOCAL_SRC_FILES := accessorychat.c
+
+LOCAL_MODULE := accessorychat
+
+LOCAL_C_INCLUDES += bionic/libc/kernel/common
+LOCAL_STATIC_LIBRARIES := libusbhost libcutils
+LOCAL_LDLIBS += -lpthread
+LOCAL_CFLAGS := -g -O0
+
+include $(BUILD_HOST_EXECUTABLE)
+
+endif
+
+# Build for device
+include $(CLEAR_VARS)
+
+LOCAL_MODULE_TAGS := optional
+
+LOCAL_SRC_FILES := accessorychat.c
+
+LOCAL_MODULE := accessorychat
+
+LOCAL_SHARED_LIBRARIES := libusbhost libcutils
+
+include $(BUILD_EXECUTABLE)
diff --git a/libs/usb/tests/AccessoryChat/accessorychat/accessorychat.c b/libs/usb/tests/AccessoryChat/accessorychat/accessorychat.c
new file mode 100644
index 0000000..94cc0ce
--- /dev/null
+++ b/libs/usb/tests/AccessoryChat/accessorychat/accessorychat.c
@@ -0,0 +1,174 @@
+/*
+ * Copyright (C) 2011 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <unistd.h>
+#include <stdio.h>
+#include <string.h>
+#include <stdlib.h>
+
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <errno.h>
+#include <pthread.h>
+
+#include <usbhost/usbhost.h>
+#include <linux/usb/f_accessory.h>
+
+struct usb_device *sDevice = NULL;
+
+static void* read_thread(void* arg) {
+    int endpoint = (int)arg;
+    int ret = 0;
+
+    while (sDevice && ret >= 0) {
+        char    buffer[16384];
+
+        ret = usb_device_bulk_transfer(sDevice, endpoint, buffer, sizeof(buffer), 1000);
+        if (ret < 0 && errno == ETIMEDOUT)
+            ret = 0;
+        if (ret > 0) {
+            fwrite(buffer, 1, ret, stdout);
+            printf("\n");
+            fflush(stdout);
+        }
+    }
+
+    return NULL;
+}
+
+static void* write_thread(void* arg) {
+    int endpoint = (int)arg;
+    int ret = 0;
+
+    while (ret >= 0) {
+        char    buffer[16384];
+        char *line = fgets(buffer, sizeof(buffer), stdin);
+        if (!line || !sDevice)
+            break;
+        ret = usb_device_bulk_transfer(sDevice, endpoint, line, strlen(line), 1000);
+    }
+
+    return NULL;
+}
+
+static void send_string(struct usb_device *device, int index, const char* string) {
+    int ret = usb_device_control_transfer(device, USB_DIR_OUT | USB_TYPE_VENDOR,
+            ACCESSORY_SEND_STRING, 0, index, (void *)string, strlen(string) + 1, 0);
+}
+
+static int usb_device_added(const char *devname, void* client_data) {
+    struct usb_descriptor_header* desc;
+    struct usb_descriptor_iter iter;
+    uint16_t vendorId, productId;
+    int ret;
+    pthread_t th;
+
+    struct usb_device *device = usb_device_open(devname);
+    if (!device) {
+        fprintf(stderr, "usb_device_open failed\n");
+        return 0;
+    }
+
+    vendorId = usb_device_get_vendor_id(device);
+    productId = usb_device_get_product_id(device);
+
+    if (vendorId == 0x18D1 || vendorId == 0x22B8) {
+        if (!sDevice && (productId == 0x2D00 || productId == 0x2D01)) {
+            struct usb_descriptor_header* desc;
+            struct usb_descriptor_iter iter;
+            struct usb_interface_descriptor *intf = NULL;
+            struct usb_endpoint_descriptor *ep1 = NULL;
+            struct usb_endpoint_descriptor *ep2 = NULL;
+
+            printf("Found android device in accessory mode\n");
+            sDevice = device;
+
+            usb_descriptor_iter_init(device, &iter);
+            while ((desc = usb_descriptor_iter_next(&iter)) != NULL && (!intf || !ep1 || !ep2)) {
+                if (desc->bDescriptorType == USB_DT_INTERFACE) {
+                    intf = (struct usb_interface_descriptor *)desc;
+                } else if (desc->bDescriptorType == USB_DT_ENDPOINT) {
+                    if (ep1)
+                        ep2 = (struct usb_endpoint_descriptor *)desc;
+                    else
+                        ep1 = (struct usb_endpoint_descriptor *)desc;
+                }
+            }
+
+            if (!intf) {
+                fprintf(stderr, "interface not found\n");
+                exit(1);
+            }
+            if (!ep1 || !ep2) {
+                fprintf(stderr, "endpoints not found\n");
+                exit(1);
+            }
+
+            if (usb_device_claim_interface(device, intf->bInterfaceNumber)) {
+                fprintf(stderr, "usb_device_claim_interface failed errno: %d\n", errno);
+                exit(1);
+            }
+
+            if ((ep1->bEndpointAddress & USB_ENDPOINT_DIR_MASK) == USB_DIR_IN) {
+                pthread_create(&th, NULL, read_thread, (void *)ep1->bEndpointAddress);
+                pthread_create(&th, NULL, write_thread, (void *)ep2->bEndpointAddress);
+            } else {
+                pthread_create(&th, NULL, read_thread, (void *)ep2->bEndpointAddress);
+                pthread_create(&th, NULL, write_thread, (void *)ep1->bEndpointAddress);
+            }
+        } else {
+            printf("Found possible android device - attempting to switch to accessory mode\n");
+
+            send_string(device, ACCESSORY_STRING_MANUFACTURER, "Google, Inc.");
+            send_string(device, ACCESSORY_STRING_MODEL, "AccessoryChat");
+            send_string(device, ACCESSORY_STRING_TYPE, "Sample Program");
+            send_string(device, ACCESSORY_STRING_VERSION, "1.0");
+
+            ret = usb_device_control_transfer(device, USB_DIR_OUT | USB_TYPE_VENDOR,
+                    ACCESSORY_START, 0, 0, 0, 0, 0);
+            return 0;
+        }
+    }
+
+    if (device != sDevice)
+        usb_device_close(device);
+
+    return 0;
+}
+
+static int usb_device_removed(const char *devname, void* client_data) {
+    if (sDevice && !strcmp(usb_device_get_name(sDevice), devname)) {
+        usb_device_close(sDevice);
+        sDevice = NULL;
+        // exit when we are disconnected
+        return 1;
+    }
+    return 0;
+}
+
+
+int main(int argc, char* argv[]) {
+    struct usb_host_context* context = usb_host_init();
+    if (!context) {
+        fprintf(stderr, "usb_host_init failed");
+        return 1;
+    }
+
+    // this will never return so it is safe to pass thiz directly
+    usb_host_run(context, usb_device_added, usb_device_removed, NULL, NULL);
+    return 0;
+}
diff --git a/libs/usb/tests/AccessoryChat/res/layout/accessory_chat.xml b/libs/usb/tests/AccessoryChat/res/layout/accessory_chat.xml
new file mode 100644
index 0000000..596ecbf
--- /dev/null
+++ b/libs/usb/tests/AccessoryChat/res/layout/accessory_chat.xml
@@ -0,0 +1,47 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!-- Copyright (C) 2011 The Android Open Source Project
+
+     Licensed under the Apache License, Version 2.0 (the "License");
+     you may not use this file except in compliance with the License.
+     You may obtain a copy of the License at
+
+          http://www.apache.org/licenses/LICENSE-2.0
+
+     Unless required by applicable law or agreed to in writing, software
+     distributed under the License is distributed on an "AS IS" BASIS,
+     WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+     See the License for the specific language governing permissions and
+     limitations under the License.
+-->
+
+<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    android:layout_width="match_parent"
+    android:layout_height="match_parent"
+    android:orientation="vertical"
+    >
+
+    <ScrollView android:id="@+id/scroll"
+        android:layout_width="match_parent"
+        android:layout_height="0px"
+        android:layout_weight="1"
+        >
+        <TextView android:id="@+id/log"
+            android:layout_width="match_parent"
+            android:layout_height="wrap_content"
+            android:layout_marginTop="25dp"
+            android:textSize="12sp"
+            android:textColor="#ffffffff"
+            />
+    </ScrollView>
+
+    <EditText android:id="@+id/message"
+        android:layout_width="match_parent"
+        android:layout_height="wrap_content"
+        android:capitalize="sentences"
+        android:autoText="true"
+        android:singleLine="true"
+        />
+
+</LinearLayout>
+
+
diff --git a/libs/usb/tests/AccessoryChat/res/xml/accessory_filter.xml b/libs/usb/tests/AccessoryChat/res/xml/accessory_filter.xml
new file mode 100644
index 0000000..588946f
--- /dev/null
+++ b/libs/usb/tests/AccessoryChat/res/xml/accessory_filter.xml
@@ -0,0 +1,18 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!-- Copyright (C) 2011 The Android Open Source Project
+
+     Licensed under the Apache License, Version 2.0 (the "License");
+     you may not use this file except in compliance with the License.
+     You may obtain a copy of the License at
+
+          http://www.apache.org/licenses/LICENSE-2.0
+
+     Unless required by applicable law or agreed to in writing, software
+     distributed under the License is distributed on an "AS IS" BASIS,
+     WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+     See the License for the specific language governing permissions and
+     limitations under the License.
+-->
+<resources>
+    <usb-accessory manufacturer="Google, Inc." model="AccessoryChat" type="Sample Program" version="1.0" />
+</resources>
diff --git a/libs/usb/tests/AccessoryChat/src/com/google/android/accessorychat/AccessoryChat.java b/libs/usb/tests/AccessoryChat/src/com/google/android/accessorychat/AccessoryChat.java
new file mode 100644
index 0000000..0a5701c
--- /dev/null
+++ b/libs/usb/tests/AccessoryChat/src/com/google/android/accessorychat/AccessoryChat.java
@@ -0,0 +1,153 @@
+/*
+ * Copyright (C) 2011 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.google.android.accessorychat;
+
+import android.app.Activity;
+import android.content.BroadcastReceiver;
+import android.content.Context;
+import android.content.Intent;
+import android.os.Bundle;
+import android.os.Handler;
+import android.os.Message;
+import android.os.ParcelFileDescriptor;
+import android.view.KeyEvent;
+import android.view.View;
+import android.view.inputmethod.EditorInfo;
+import android.util.Log;
+import android.widget.EditText;
+import android.widget.TextView;
+
+import com.google.android.usb.UsbAccessory;
+import com.google.android.usb.UsbManager;
+
+import java.io.FileDescriptor;
+import java.io.FileInputStream;
+import java.io.FileOutputStream;
+import java.io.IOException;
+
+public class AccessoryChat extends Activity implements Runnable, TextView.OnEditorActionListener {
+
+    private static final String TAG = "AccessoryChat";
+    TextView mLog;
+    EditText mEditText;
+    ParcelFileDescriptor mFileDescriptor;
+    FileInputStream mInputStream;
+    FileOutputStream mOutputStream;
+
+    private static final int MESSAGE_LOG = 1;
+
+    @Override
+    public void onCreate(Bundle savedInstanceState) {
+        super.onCreate(savedInstanceState);
+
+        setContentView(R.layout.accessory_chat);
+        mLog = (TextView)findViewById(R.id.log);
+        mEditText = (EditText)findViewById(R.id.message);
+        mEditText.setOnEditorActionListener(this);
+    }
+
+    @Override
+    public void onResume() {
+        super.onResume();
+
+        Intent intent = getIntent();
+        Log.d(TAG, "intent: " + intent);
+        UsbManager manager = UsbManager.getInstance();
+        UsbAccessory[] accessories = manager.getAccessoryList();
+        UsbAccessory accessory = (accessories == null ? null : accessories[0]);
+        if (accessory != null) {
+            mFileDescriptor = manager.openAccessory(accessory);
+            if (mFileDescriptor != null) {
+                FileDescriptor fd = mFileDescriptor.getFileDescriptor();
+                mInputStream = new FileInputStream(fd);
+                mOutputStream = new FileOutputStream(fd);
+                Thread thread = new Thread(null, this, "AccessoryChat");
+                thread.start();
+            } else {
+                Log.d(TAG, "openAccessory fail");
+            }
+        } else {
+            Log.d(TAG, "mAccessory is null");
+        }
+    }
+
+    @Override
+    public void onPause() {
+        super.onPause();
+        if (mFileDescriptor != null) {
+            try {
+                mFileDescriptor.close();
+            } catch (IOException e) {
+            } finally {
+                mFileDescriptor = null;
+            }
+        }
+    }
+
+    @Override
+    public void onDestroy() {
+       super.onDestroy();
+    }
+
+    public boolean onEditorAction(TextView v, int actionId, KeyEvent event) {
+        if (actionId == EditorInfo.IME_ACTION_DONE && mOutputStream != null) {
+            try {
+                mOutputStream.write(v.getText().toString().getBytes());
+            } catch (IOException e) {
+                Log.e(TAG, "write failed", e);
+            }
+            v.setText("");
+            return true;
+        }
+        Log.d(TAG, "onEditorAction " + actionId + " event: " + event);
+        return false;
+    }
+
+    public void run() {
+        int ret = 0;
+        byte[] buffer = new byte[16384];
+        while (ret >= 0) {
+            try {
+                ret = mInputStream.read(buffer);
+            } catch (IOException e) {
+                break;
+            }
+
+            if (ret > 0) {
+                Message m = Message.obtain(mHandler, MESSAGE_LOG);
+                String text = new String(buffer, 0, ret);
+                Log.d(TAG, "chat: " + text);
+                m.obj = text;
+                mHandler.sendMessage(m);
+            }
+        }
+        Log.d(TAG, "thread out");
+    }
+
+   Handler mHandler = new Handler() {
+        @Override
+        public void handleMessage(Message msg) {
+            switch (msg.what) {
+                case MESSAGE_LOG:
+                    mLog.setText(mLog.getText() + "\n" + (String)msg.obj);
+                    break;
+             }
+        }
+    };
+}
+
+