7.7. USB

Device implementations SHOULD support USB peripheral mode and SHOULD support USB host mode.

7.7.1. USB peripheral mode

If a device implementation includes a USB port supporting peripheral mode:

  • The port MUST be connectable to a USB host that has a standard type-A or type-C USB port.
  • The port SHOULD use micro-B, micro-AB or Type-C USB form factor. Existing and new Android devices are STRONGLY RECOMMENDED to meet these requirements so they will be able to upgrade to the future platform releases.
  • The port SHOULD be located on the bottom of the device (according to natural orientation) or enable software screen rotation for all apps (including home screen), so that the display draws correctly when the device is oriented with the port at bottom. Existing and new Android devices are STRONGLY RECOMMENDED to meet these requirements so they will be able to upgrade to future platform releases.
  • It MUST allow a USB host connected with the Android device to access the contents of the shared storage volume using either USB mass storage or Media Transfer Protocol.
  • It SHOULD implement the Android Open Accessory (AOA) API and specification as documented in the Android SDK documentation, and if it is an Android Handheld device it MUST implement the AOA API. Device implementations implementing the AOA specification:
    • MUST declare support for the hardware feature android.hardware.usb.accessory.
    • MUST implement the USB audio class as documented in the Android SDK documentation.
    • The USB mass storage class MUST include the string “android” at the end of the interface description iInterface string of the USB mass storage
  • It SHOULD implement support to draw 1.5 A current during HS chirp and traffic as specified in the USB Battery Charging specification, revision 1.2. Existing and new Android devices are STRONGLY RECOMMENDED to meet these requirements so they will be able to upgrade to the future platform releases.
  • Type-C devices MUST detect 1.5A and 3.0A chargers per the Type-C resistor standard and it must detect changes in the advertisement.
  • Type-C devices also supporting USB host mode are STRONGLY RECOMMENDED to support Power Delivery for data and power role swapping.
  • Type-C devices SHOULD support Power Delivery for high-voltage charging and support for Alternate Modes such as display out.
  • The value of iSerialNumber in USB standard device descriptor MUST be equal to the value of android.os.Build.SERIAL.
  • Type-C devices are STRONGLY RECOMMENDED to not support proprietary charging methods that modify Vbus voltage beyond default levels, or alter sink/source roles as such may result in interoperability issues with the chargers or devices that support the standard USB Power Delivery methods. While this is called out as “STRONGLY RECOMMENDED”, in future Android versions we might REQUIRE all type-C devices to support full interoperability with standard type-C chargers.

7.7.2. USB host mode

If a device implementation includes a USB port supporting host mode, it:

  • SHOULD use a type-C USB port, if the device implementation supports USB 3.1.
  • MAY use a non-standard port form factor, but if so MUST ship with a cable or cables adapting the port to a standard type-A or type-C USB port.
  • MAY use a micro-AB USB port, but if so SHOULD ship with a cable or cables adapting the port to a standard type-A or type-C USB port.
  • is STRONGLY RECOMMENDED to implement the USB audio class as documented in the Android SDK documentation.
  • MUST implement the Android USB host API as documented in the Android SDK, and MUST declare support for the hardware feature android.hardware.usb.host.
  • SHOULD support device charging while in host mode; advertising a source current of at least 1.5A as specified in the Termination Parameters section of the [USB Type-C Cable and Connector Specification Revision 1.2] (http://www.usb.org/developers/docs/usb_31_021517.zip) for USB Type-C connectors or using Charging Downstream Port(CDP) output current range as specified in the USB Battery Charging specifications, revision 1.2 for Micro-AB connectors.
  • USB Type-C devices are STRONGLY RECOMMENDED to support DisplayPort, SHOULD support USB SuperSpeed Data Rates, and are STRONGLY RECOMMENDED to support Power Delivery for data and power role swapping.
  • Devices with any type-A or type-AB ports MUST NOT ship with an adapter converting from this port to a type-C receptacle.
  • MUST recognize any remotely connected MTP (Media Transfer Protocol) devices and make their contents accessible through the ACTION_GET_CONTENT, ACTION_OPEN_DOCUMENT, and ACTION_CREATE_DOCUMENT intents, if the Storage Access Framework (SAF) is supported.
  • MUST, if using a Type-C USB port and including support for peripheral mode, implement Dual Role Port functionality as defined by the USB Type-C specification (section 4.5.1.3.3).
  • SHOULD, if the Dual Role Port functionality is supported, implement the Try.* model that is most appropriate for the device form factor. For example a handheld device SHOULD implement the Try.SNK model.