<ol>
<li><a href="https://developers.google.com/events/io/sessions/gooio2012/128/">
Google I/O Session Video</a></li>
- <li><a href="aoa.html">Android Open Accessory Protocol</a></li>
- <li><a href="aoa2.html">Android Open Accessory Protocol 2.0</a></li>
+ <li><a href="http://source.android.com/tech/accessories/aoap/aoa.html">
+ Android Open Accessory Protocol</a></li>
+ <li><a href="http://source.android.com/tech/accessories/aoap/aoa2.html">
+ Android Open Accessory Protocol 2.0</a></li>
<li><a href="{@docRoot}guide/topics/connectivity/usb/accessory.html">
USB Accessory Dev Guide</a></li>
</ol>
</div>
</div>
-<p>The Android Accessory Development Kit (ADK) for 2012 is the latest reference implementation of
-an <a href="aoa.html">Android Open Accessory</a> device, designed to help Android hardware accessory
-builders and software developers create accessories for Android. The ADK 2012 is based on the <a
-href="http://arduino.cc">Arduino</a> open source electronics prototyping platform, with some
-hardware and software extensions that allow it to communicate with Android devices.</p>
+<p>The Android Accessory Development Kit (ADK) for 2012 is the latest reference implementation of an
+<a href="http://source.android.com/tech/accessories/index.html">Android Open Accessory</a> device,
+designed to help Android hardware accessory builders and software developers create accessories
+for Android. The ADK 2012 is based on the <a href="http://arduino.cc">Arduino</a> open source
+electronics prototyping platform, with some hardware and software extensions that allow it to
+communicate with Android devices.</p>
<p>A limited number of these kits were produced and distributed at the Google I/O 2012 developer
conference. If you did not receive one of these kits, fear not! The specifications and design files
L.accessorySend(outmsg, outmsgLen);
}
L.adkEventProcess();
-}
+}
</pre>
<p>For more details, review the implementations of these methods in the {@code clock.ino}
<p>One of the important new features introduced with the ADK 2012 is the ability to play audio over
a USB connection. This innovation was introduced as an update to Android Open Accessory (AOA)
-<a href="aoa2.html">protocol 2.0</a> and is available on devices running Android 4.1 (API Level 16)
-and higher.</p>
+<a href="http://source.android.com/tech/accessories/aoap/aoa2.html">protocol 2.0</a> and is
+available on devices running Android 4.1 (API Level 16) and higher.</p>
<p>The ADK 2012 provides a reference implementation of this functionality for accessory developers.
No software application is required to be installed on the connected Android device, accessory
+++ /dev/null
-page.title=Android Open Accessory Protocol
-@jd:body
-
-<div id="qv-wrapper">
- <div id="qv">
- <h2>In this document</h2>
- <ol>
- <li><a href="#accessory-protocol">Implementing the Android Accessory Protocol</a>
- <ol>
- <li><a href="#wait">Wait for and detect connected devices</a></li>
- <li><a href="#determine">Determine the device's accessory mode support</a></li>
- <li><a href="#start">Attempt to start the device in accessory mode</a></li>
- <li><a href="#establish">Establish communication with the device</a></li>
- </li>
- </ol>
-
- <h2>See also</h2>
- <ol>
- <li><a href="aoa2.html">Android Open Accessory Protocol 2.0</a></li>
- <li><a href="{@docRoot}guide/topics/connectivity/usb/accessory.html">USB Accessory Dev
-Guide</a></li>
- </ol>
- </div>
- </div>
-
- <p>With Android 3.1, the platform introduces Android Open Accessory
- support, which allows external USB hardware (an Android USB accessory) to interact with an
- Android-powered device in a special accessory mode. When an Android-powered powered device is
- in accessory mode, the connected accessory acts as the USB host (powers the bus and enumerates
- devices) and the Android-powered device acts as the USB device. Android USB accessories are
- specifically designed to attach to Android-powered devices and adhere to a simple protocol
- (Android accessory protocol) that allows them to detect Android-powered devices that support
- accessory mode. Accessories must also provide 500mA at 5V for charging power. Many previously
- released Android-powered devices are only capable of acting as a USB device and cannot initiate
- connections with external USB devices. Android Open Accessory support overcomes this limitation
- and allows you to build accessories that can interact with an assortment of Android-powered
- devices by allowing the accessory to initiate the connection.</p>
-
- <p class="note"><strong>Note:</strong> Accessory mode is ultimately dependent on the device's
- hardware and not all devices support accessory mode. Devices that support accessory mode can
- be filtered using a <code><uses-feature></code> element in your corresponding application's
- Android manifest. For more information, see the <a href=
- "{@docRoot}guide/topics/connectivity/usb/accessory.html#manifest">USB Accessory</a> developer
-guide.</p>
-
- <h2 id="accessory-protocol">Implementing the Android Accessory Protocol</h2>
-
- <p>An Android USB accessory must adhere to Android Accessory Protocol, which defines how
- an accessory detects and sets up communication with an Android-powered device. In general, an
- accessory should carry out the following steps:</p>
-
- <ol>
- <li>Wait for and detect connected devices</li>
-
- <li>Determine the device's accessory mode support</li>
-
- <li>Attempt to start the device in accessory mode if needed</li>
-
- <li>Establish communication with the device if it supports the Android accessory protocol</li>
- </ol>
-
- <p>The following sections go into depth about how to implement these steps.</p>
-
- <h3 id="wait">Wait for and detect connected devices</h3>
-
- <p>Your accessory should have logic to continuously check
- for connected Android-powered devices. When a device is connected, your accessory should
- determine if the device supports accessory mode.</p>
-
- <h3 id="determine">Determine the device's accessory mode support</h3>
-
-
- <p>When an Android-powered device is connected, it can be in one of three states:</p>
-
- <ol type="a">
- <li>The attached device supports Android accessory mode and is already in accessory mode.</li>
-
- <li>The attached device supports Android accessory mode, but it is not in accessory mode.</li>
-
- <li>The attached device does not support Android accessory mode.</li>
- </ol>
-
- <p>During the initial connection, the accessory should check the vendor and product IDs of the
- connected device's USB device descriptor. The vendor ID should match Google's ID (0x18D1) and the
- product ID should be 0x2D00 or 0x2D01 if the device is already in accessory mode (case A). If so,
- the accessory can now <a href="#establish">establish communication with the device</a> through
- bulk transfer endpoints with its own communication protocol. There is no need to start the device
- in accessory mode.</p>
-
- <p class="note"><strong>Note:</strong> 0x2D00 is reserved for Android-powered devices that
- support accessory mode. 0x2D01 is reserved for devices that support accessory mode as well as the
- ADB (Android Debug Bridge) protocol, which exposes a second interface with two bulk endpoints for
- ADB. You can use these endpoints for debugging the accessory application if you are simulating
- the accessory on a computer. In general, do not use this interface unless your accessory is
- implementing a passthrough to ADB on the device.</p>
-
- <p>If the vendor and product ID do not match, there is no way to distinguish between states b and
- c, so the accessory <a href="#start">attempts to start the device in accessory mode</a> to figure
- out if the device is supported.</p>
-
- <h3 id="start">Attempt to start the device in accessory mode</h3>
-
- <p>If the vendor and product IDs do not correspond to an Android-powered device in accessory
- mode, the accessory cannot discern whether the device supports accessory mode and is not in that
- state, or if the device does not support accessory mode at all. This is because devices that
- support accessory mode but aren't in it initially report the device's manufacturer vendor ID and
- product ID, and not the special Android Open Accessory ones. In either case, the accessory should
-try to start
- the device into accessory mode to figure out if the device supports it. The following steps
- explain how to do this:</p>
-
- <ol>
- <li>Send a 51 control request ("Get Protocol") to figure out if the device supports the Android
- accessory protocol. A non-zero number is returned if the protocol is supported, which
- represents the version of the protocol that the device supports (currently, only version 1
- exists). This request is a control request on endpoint 0 with the following characteristics:
- <pre>
-requestType: USB_DIR_IN | USB_TYPE_VENDOR
-request: 51
-value: 0
-index: 0
-data: protocol version number (16 bits little endian sent from the device to the
-accessory)
-</pre>
- </li>
-
- <li>If the device returns a proper protocol version, send identifying string information to the
- device. This information allows the device to figure out an appropriate application for this
- accessory and also present the user with a URL if an appropriate application does not exist.
- These requests are control requests on endpoint 0 (for each string ID) with the following
- characteristics:
- <pre>
-requestType: USB_DIR_OUT | USB_TYPE_VENDOR
-request: 52
-value: 0
-index: string ID
-data zero terminated UTF8 string sent from accessory to device
-</pre>
-
- <p>The following string IDs are supported, with a maximum size of 256 bytes for each string
- (must be zero terminated with \0).</p>
- <pre>
-manufacturer name: 0
-model name: 1
-description: 2
-version: 3
-URI: 4
-serial number: 5
-</pre>
- </li>
-
- <li>When the identifying strings are sent, request the device start up in accessory mode. This
- request is a control request on endpoint 0 with the following characteristics:
- <pre>
-requestType: USB_DIR_OUT | USB_TYPE_VENDOR
-request: 53
-value: 0
-index: 0
-data: none
-</pre>
- </li>
- </ol>
-
- <p>After sending the final control request, the connected USB device should re-introduce itself
- on the bus in accessory mode and the accessory can re-enumerate the connected devices. The
- algorithm jumps back to <a href="#determine">determining the device's accessory mode support</a>
- to check for the vendor and product ID. The vendor ID and product ID of the device will be
- different if the device successfully switched to accessory mode and will now correspond to
- Google's vendor and product IDs instead of the device manufacturer's IDs. The accessory can now
- <a href="#establish">establish communication with the device</a>.</p>
-
- <p>If at any point these steps fail, the device does not support Android accessory mode and the
- accessory should wait for the next device to be connected.</p>
-
- <h3 id="establish">Establish communication with the device</h3>
-
- <p>If an Android-powered device in accessory mode is detected, the accessory can query the
- device's interface and endpoint descriptors to obtain the bulk endpoints to communicate with the
- device. An Android-powered device that has a product ID of 0x2D00 has one interface with two bulk
- endpoints for input and output communication. A device with product ID of 0x2D01 has two
- interfaces with two bulk endpoints each for input and output communication. The first interface
- is for standard communication while the second interface is for ADB communication. To communicate
- on an interface, all you need to do is find the first bulk input and output endpoints, set the
- device's configuration to a value of 1 with a SET_CONFIGURATION (0x09) device request, then
- communicate using the endpoints.</p>
-
+++ /dev/null
-page.title=Android Open Accessory Protocol 2.0
-@jd:body
-
-<div id="qv-wrapper">
- <div id="qv">
- <h2>In this document</h2>
- <ol>
- <li><a href="#detecting">Detecting Android Open Accessory 2.0 Support</a></li>
- <li><a href="#audio-support">Audio Support</a></li>
- <li><a href="#hid">HID Support</a></li>
- <li><a href="#interop-aoa">Interoperability with AOA 1.0 Features</a></li>
- <li><a href="#no-app-conn">Connecting AOA 2.0 without an Android App</a></li>
- </ol>
-
- <h2>See also</h2>
- <ol>
- <li><a href="aoa.html">Android Open Accessory Protocol</a></li>
- </ol>
- </div>
-</div>
-
-<p>This document describes the changes to the Android Open Accessory (AOA) protocol since its
-initial release, and is a supplement to the documentation of the <a href="aoa.html">first
-release of AOA</a>.</p>
-
-<p>The Android Open Accessory Protocol 2.0 adds two new features: audio output (from the Android
-device to the accessory) and support for the accessory acting as one or more human interface devices
-(HID) to the Android device. The Android SDK APIs available to Android application developers
-remain unchanged.</p>
-
-<h2 id="detecting">Detecting Android Open Accessory 2.0 Support</h2>
-
-<p>In order for an accessory to determine if a connected Android device supports accessories and at
-what protocol level, the accessory must send a {@code getProtocol()} command and check the result.
-Android devices supporting the initial version of the Android Open Accessory protocol return a
-{@code 1}, representing the protocol version number. Devices that support the new features described
-in this document must return {@code 2} for the protocol version. Version 2.0 of the protocol is
-upwardly compatible, so accessories designed for the original accessory protocol still work
-with newer Android devices. The following code from the <a href="adk.html">Android Development Kit
-2011</a> {@code AndroidAccessory} library demonstrates this protocol check:</p>
-
-<pre>
-bool AndroidAccessory::switchDevice(byte addr)
-{
- int protocol = getProtocol(addr);
- if (protocol >= 1) {
- Serial.print("device supports protocol 1 or higher\n");
- } else {
- Serial.print("could not read device protocol version\n");
- return false;
- }
-
- sendString(addr, ACCESSORY_STRING_MANUFACTURER, manufacturer);
- sendString(addr, ACCESSORY_STRING_MODEL, model);
- sendString(addr, ACCESSORY_STRING_DESCRIPTION, description);
- sendString(addr, ACCESSORY_STRING_VERSION, version);
- sendString(addr, ACCESSORY_STRING_URI, uri);
- sendString(addr, ACCESSORY_STRING_SERIAL, serial);
-
- usb.ctrlReq(addr, 0, USB_SETUP_HOST_TO_DEVICE | USB_SETUP_TYPE_VENDOR |
-USB_SETUP_RECIPIENT_DEVICE,
- ACCESSORY_START, 0, 0, 0, 0, NULL);
- return true;
-}
-</pre>
-
-<p>AOA 2.0 includes new USB product IDs, one for each combination of USB interfaces available when
-in accessory mode. The possible USB interfaces are:</p>
-
-<ul>
- <li><strong>accessory</strong> - An interface providing 2 bulk endpoints for communicating with an
-Android application.</li>
- <li><strong>audio</strong> -A new standard USB audio class interface for streaming audio
-from an Android device to an accessory.</li>
- <li><strong>adb</strong> - An interface intended only for debugging purposes while developing an
-accessory. Only enabled if the user has USB Debugging enabled in Settings on the Android device.
- </li>
-</ul>
-
-<p>In AOA 1.0, there are only two USB product IDs:</p>
-
-<ul>
- <li>{@code 0x2D00} - accessory</li>
- <li>{@code 0x2D01} - accessory + adb</li>
-</ul>
-
-<p>AOA 2.0 adds an optional USB audio interface and, therefore, includes product IDs for the new
-combinations of USB interfaces:</p>
-
-<ul>
- <li>{@code 0x2D02} - audio</li>
- <li>{@code 0x2D03} - audio + adb</li>
- <li>{@code 0x2D04} - accessory + audio</li>
- <li>{@code 0x2D05} - accessory + audio + adb</li>
-</ul>
-
-<h2 id="audio-support">Audio Support</h2>
-
-<p>AOA 2.0 includes optional support for audio output from an Android device to an accessory. This
-version of the protocol supports a standard USB audio class interface that is capable of 2 channel
-16-bit PCM audio with a bit rate of 44100 Khz. AOA 2.0 is currently limited to this output mode, but
-additional audio modes may be added in the future.</p>
-
-<p>To enable the audio support, the accessory must send a new USB control request:</p>
-
-<pre>
-<strong>SET_AUDIO_MODE</strong>
-requestType: USB_DIR_OUT | USB_TYPE_VENDOR
-request: 58
-value: 0 for no audio (default),
- 1 for 2 channel, 16-bit PCM at 44100 KHz
-index: 0
-data none
-</pre>
-
-<p>This command must be sent <em>before</em> sending the {@code ACCESSORY_START} command for
-entering accessory mode.</p>
-
-<h2 id="hid">HID Support</h2>
-
-<p>AOA 2.0 allows the accessory to register one or more HID devices with
-an Android device. This approach reverses the direction of communication for typical USB HID
-devices like USB mice and keyboards. Normally, the HID device is a peripheral connected to a USB
-host like a personal computer. But in the case of the AOA protocol, the USB host acts as one or more
-input devices to a USB peripheral.</p>
-
-<p>HID support in AOA 2.0 is simply a proxy for standard HID events. The implementation makes no
-assumptions about the content or type of events and merely passes it through to the input system,
-so an AOA 2.0 accessory can act as any HID device (mouse, keyboard, game controller, etc.). It
-can be used for something as simple as the play/pause button on a media dock, or something as
-complicated as a docking station with a mouse and full QWERTY keyboard.</p>
-
-<p>The AOA 2.0 protocol adds four new USB control requests to allow the accessory to act as one or
-more HID input devices to the Android device. Since HID support is done entirely through
-control requests on endpoint zero, no new USB interface is needed to provide this support. The
-control requests are as follows:</p>
-
-<ul>
- <li><strong>ACCESSORY_REGISTER_HID</strong> registers a new HID device with the Android device.
-The accessory provides an ID number that is used to identify the HID device for the other three
-calls. This ID is valid until USB is disconnected or until the accessory sends
-ACCESSORY_UNREGISTER_HID to unregister the HID device.</li>
- <li><strong>ACCESSORY_UNREGISTER_HID</strong> unregisters a HID device that was previously
-registered with ACCESSORY_REGISTER_HID.</li>
- <li><strong>ACCESSORY_SET_HID_REPORT_DESC</strong> sends a report descriptor for a HID device to
-the Android device. This request is used to describe the capabilities of the HID device, and must
-be sent before reporting any HID events to the Android device. If the report descriptor is larger
-than the maximum packet size for endpoint zero, multiple ACCESSORY_SET_HID_REPORT_DESC commands are
-sent in order to transfer the entire descriptor.</li>
- <li><strong>ACCESSORY_SEND_HID_EVENT</strong> sends input events from the accessory to the Android
-device.</li>
-</ul>
-
-<p>The code definitions for these new control requests are as follows:</p>
-
-<pre>
-/* Control request for registering a HID device.
- * Upon registering, a unique ID is sent by the accessory in the
- * value parameter. This ID will be used for future commands for
- * the device
- *
- * requestType: USB_DIR_OUT | USB_TYPE_VENDOR
- * request: ACCESSORY_REGISTER_HID_DEVICE
- * value: Accessory assigned ID for the HID device
- * index: total length of the HID report descriptor
- * data none
- */
-#define ACCESSORY_REGISTER_HID 54
-
-/* Control request for unregistering a HID device.
- *
- * requestType: USB_DIR_OUT | USB_TYPE_VENDOR
- * request: ACCESSORY_REGISTER_HID
- * value: Accessory assigned ID for the HID device
- * index: 0
- * data none
- */
-#define ACCESSORY_UNREGISTER_HID 55
-
-/* Control request for sending the HID report descriptor.
- * If the HID descriptor is longer than the endpoint zero max packet size,
- * the descriptor will be sent in multiple ACCESSORY_SET_HID_REPORT_DESC
- * commands. The data for the descriptor must be sent sequentially
- * if multiple packets are needed.
- *
- * requestType: USB_DIR_OUT | USB_TYPE_VENDOR
- * request: ACCESSORY_SET_HID_REPORT_DESC
- * value: Accessory assigned ID for the HID device
- * index: offset of data in descriptor
- * (needed when HID descriptor is too big for one packet)
- * data the HID report descriptor
- */
-#define ACCESSORY_SET_HID_REPORT_DESC 56
-
-/* Control request for sending HID events.
- *
- * requestType: USB_DIR_OUT | USB_TYPE_VENDOR
- * request: ACCESSORY_SEND_HID_EVENT
- * value: Accessory assigned ID for the HID device
- * index: 0
- * data the HID report for the event
- */
-#define ACCESSORY_SEND_HID_EVENT 57
-</pre>
-
-<h2 id="interop-aoa">Interoperability with AOA 1.0 Features</h2>
-
-<p>The original <a href="aoa.html">AOA protocol</a> provided support for an Android application to
-communicate directly with a USB host (accessory) over USB. AOA 2.0 keeps that support, but adds new
-features to allow the accessory to communicate with the Android operating system itself
-(specifically the audio and input systems). The design of the AOA 2.0 makes it is possible to build
-an accessory that also makes use of the new audio and/or HID support in addition to the original
-feature set. Simply use the new features described in this document in addition to the original AOA
-protocol features.</p>
-
-<h2 id="no-app-conn">Connecting AOA 2.0 without an Android App</h2>
-
-<p>It is possible to design an accessory (for example, an audio dock) that uses the new audio and
-HID support, but does not need to communicate with an application on the Android device. In that
-case, the user would not want to see the dialog prompts related to finding and associating the newly
-attached accessory with an Android application that can communicate with it. To prevent these
-dialogs from appearing after the device and accessory are connected, the accessory can simply not
-send the manufacturer and model names to the Android device. If these strings are not provided to
-the Android device, then the accessory is able to make use of the new audio and HID support in AOA
-2.0 without the system attempting to find an application to communicate with the accessory. Also,
-if these strings are not provided, the accessory USB interface is not present in the Android
-device USB configuration after the device enters accessory mode.</p>
\ No newline at end of file
Android.</p>
<p>Accessories use the Android Open Accessory (AOA) protocol to communicate with Android
-devices, over USB cable or through a Bluetooth connection. If you are building an accessory for
-Android devices, make sure you review the information below to understand about how to implement the
-AOA protocol.</p>
+devices, over a USB cable or through a Bluetooth connection. If you are building an accessory that
+uses USB, make sure you understand how to implement the AOA protocol to establish communication
+between your accessory hardware and Android. For more information, see the
+<a href="http://source.android.com/tech/accessories/index.html">Android Open Acessory protocol</a>.
+</p>
<p>The following sections provide more information about the Android Accessory Development Kits, how
to use them, and how to get started building your own accessories for Android.</p>
<dt><a href="adk.html">ADK 2011 Guide</a></dt>
<dd>Guide to getting started with the original ADK, released at Google I/O 2011.</dd>
-
- <dt><a href="aoa.html">Android Open Accessory Protocol</a></dt>
- <dd>Guide to implementing the Android Open Accessory Protocol.</dd>
-
- <dt><a href="aoa2.html">Android Open Accessory Protocol 2.0</a></dt>
- <dd>A description and guide to implementing the extended Android Open Accessory Protocol which
- supports audio dock accessories.</dd>
</dl>
<ul>
<li><a href="<?cs var:toroot ?>tools/adk/adk2.html">ADK 2012 Guide</a></li>
<li><a href="<?cs var:toroot ?>tools/adk/adk.html">ADK 2011 Guide</a></li>
- <li class="nav-section">
- <div class="nav-section-header">
- <a href="<?cs var:toroot ?>tools/adk/aoa.html">Android Open Accessory Protocol</a>
- </div>
- <ul>
- <li><a href="<?cs var:toroot ?>tools/adk/aoa2.html">AOA 2.0</a></li>
- </ul>
- </li>
</ul>
</li>
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