USB host and accessory overview
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Android supports a variety of USB peripherals and Android USB accessories
(hardware that implements the Android accessory protocol) through two modes: USB
accessory and USB host. In USB accessory mode, the external USB hardware acts as
the USB host. Examples of accessories might include:
- robotics controllers
- docking stations
- diagnostic and musical equipment
- kiosks
- card readers
and many more. This gives Android-powered devices that don't have host
capabilities the ability to interact with USB hardware. Android
USB accessories must be
designed to work with Android-powered devices and must adhere to the Android
accessory communication protocol. In
USB host mode, the Android-powered device acts as the host. Examples of devices
include digital cameras, keyboards, mice, and game controllers. USB devices that
are designed for a wide range of applications and environments can still
interact with Android applications that can correctly communicate with the
device.
Figure 1 shows the differences between the two modes. When the Android-powered
device is in host mode, it acts as the USB host and powers the bus. When the
Android-powered device is in USB accessory mode, the connected USB hardware (an
Android USB accessory in this case) acts as the host and powers the bus.
Figure 1. USB Host and Accessory Modes
USB accessory and host modes are directly supported in Android 3.1 (API level
12) or newer platforms. USB accessory mode is also backported to Android 2.3.4
(API level 10) as an add-on library to support a broader range of devices.
Device manufacturers can choose whether or not to include the add-on library on
the device\'s system image.
Note: Support for USB host and accessory modes are ultimately dependant on
the device\'s hardware, regardless of platform level. You can filter for devices
that support USB host and accessory through a
<uses-feature> element.
See the USB accessory and
host documentation for more details.
Debug considerations
When debugging applications that use USB accessory or host features, you most
likely have USB hardware connected to your Android-powered device. This
prevents you from having an adb connection to the Android-powered device
using USB. You can still access adb over a network connection. To enable adb
over a network connection:
- Connect the Android-powered device using USB to your computer.
- From your SDK
platform-tools/ directory, enter adb tcpip 5555 at the
command prompt.
- Enter
adb connect <device-ip-address>:5555 You should now be connected to
the Android-powered device and can issue the usual adb commands like
adb logcat.
- To set your device to listen on USB, enter
adb usb.
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Last updated 2024-01-03 UTC.
[[["Easy to understand","easyToUnderstand","thumb-up"],["Solved my problem","solvedMyProblem","thumb-up"],["Other","otherUp","thumb-up"]],[["Missing the information I need","missingTheInformationINeed","thumb-down"],["Too complicated / too many steps","tooComplicatedTooManySteps","thumb-down"],["Out of date","outOfDate","thumb-down"],["Samples / code issue","samplesCodeIssue","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2024-01-03 UTC."],[],[],null,["# USB host and accessory overview\n\nAndroid supports a variety of USB peripherals and Android USB accessories\n(hardware that implements the Android accessory protocol) through two modes: USB\naccessory and USB host. In USB accessory mode, the external USB hardware acts as\nthe USB host. Examples of accessories might include:\n\n- robotics controllers\n- docking stations\n- diagnostic and musical equipment\n- kiosks\n- card readers\n\nand many more. This gives Android-powered devices that don't have host\ncapabilities the ability to interact with USB hardware. Android\nUSB accessories must be\ndesigned to work with Android-powered devices and must adhere to the [Android\naccessory communication protocol](http://accessories.android.com/demokit). In\nUSB host mode, the Android-powered device acts as the host. Examples of devices\ninclude digital cameras, keyboards, mice, and game controllers. USB devices that\nare designed for a wide range of applications and environments can still\ninteract with Android applications that can correctly communicate with the\ndevice.\n\nFigure 1 shows the differences between the two modes. When the Android-powered\ndevice is in host mode, it acts as the USB host and powers the bus. When the\nAndroid-powered device is in USB accessory mode, the connected USB hardware (an\nAndroid USB accessory in this case) acts as the host and powers the bus.\n\n**Figure 1.** USB Host and Accessory Modes\n\nUSB accessory and host modes are directly supported in Android 3.1 (API level\n12) or newer platforms. USB accessory mode is also backported to Android 2.3.4\n(API level 10) as an add-on library to support a broader range of devices.\nDevice manufacturers can choose whether or not to include the add-on library on\nthe device\\\\'s system image.\n\n**Note:** Support for USB host and accessory modes are ultimately dependant on\nthe device\\\\'s hardware, regardless of platform level. You can filter for devices\nthat support USB host and accessory through a\n[`\u003cuses-feature\u003e`](/guide/topics/manifest/uses-feature-element) element.\nSee the USB [accessory](/develop/connectivity/usb/accessory) and\n[host](/develop/connectivity/usb/host) documentation for more details.\n\nDebug considerations\n--------------------\n\nWhen debugging applications that use USB accessory or host features, you most\nlikely have USB hardware connected to your Android-powered device. This\nprevents you from having an `adb` connection to the Android-powered device\nusing USB. You can still access `adb` over a network connection. To enable `adb`\nover a network connection:\n\n1. Connect the Android-powered device using USB to your computer.\n2. From your SDK `platform-tools/` directory, enter `adb tcpip 5555` at the command prompt.\n3. Enter `adb connect \u003cdevice-ip-address\u003e:5555` You should now be connected to the Android-powered device and can issue the usual `adb` commands like `adb logcat`.\n4. To set your device to listen on USB, enter `adb usb`."]]
