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Merge "docs: Remove Android Open Accessory docs, which are now on source.android.com" into jb-dev-docs

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Joe Fernandez
2012-10-04 13:05:12 -07:00
committed by Android (Google) Code Review
parent 688447e512 069bc4a3b6
commit e3eeeb6d03
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23
docs/html/tools/adk/adk2.jd
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@@ -28,19 +28,22 @@ page.title=Accessory Development Kit 2012 Guide
<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
@@ -537,7 +540,7 @@ void loop() {
L.accessorySend(outmsg, outmsgLen);
}
L.adkEventProcess();
}
}
</pre>
<p>For more details, review the implementations of these methods in the {@code clock.ino}
@@ -604,8 +607,8 @@ implementation details.</p>
<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

186
docs/html/tools/adk/aoa.jd
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@@ -1,186 +0,0 @@
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>&lt;uses-feature&gt;</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>

227
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@@ -1,227 +0,0 @@
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>

15
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@@ -11,9 +11,11 @@ devices, weather stations, or any other external hardware device that adds to th
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>
@@ -24,11 +26,4 @@ to use them, and how to get started building your own accessories for Android.</
<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>

8
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@@ -213,14 +213,6 @@ class="en">USB Drivers</span></a>
<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>