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Stylus

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Android 6.0 and higher supports a standard data format for Bluetooth stylus connections over Bluetooth (BT), Bluetooth Low Energy (BTLE), or USB. The platform correlates timing between touch input and stylus data then provides stylus data to render MotionEvents to the active application. The following sections provide guidelines for OEM partners, stylus accessory creators, and stylus application developers.

Guidelines for OEM partners

To enable Bluetooth stylus support, OEM partners must support Bluetooth (and should support BTLE for wider compatibility). The platform handles data collection, timing correlation, and rendering to the application for supported stylus events.

At this time, the Android CTS does not include tests to ensure existing APIs for touch events support default behavior. As a workaround, we recommend creating a stylus accessory or emulator that can simulate stylus events.

Guidelines for stylus accessory creators

To implement support on a stylus device, partners must use the Stylus Human Interface Device (HID) Descriptor shown below to describe how stylus data (pressure sensitivity, eraser, side buttons, device ID, etc.) is represented. The stylus device sends the HID information to the Android mobile device, enabling the platform to correlate HID data with touch data from the touchscreen to produce stylus events via MotionEvent. Data can be sent over Bluetooth (BT), Bluetooth Low Energy (BTLE), or USB.

HID descriptor

UsagePage(Digitizer)
Usage(Pen)
Collection(Application)
    Usage(Stylus)
    Collection(Logical)
        Usage(Tip Pressure)
        Logical Minimum(0)
        Logical Maximum(1023)
        Report Count(1)
        Report Size(10)
        Input(Data, Variable, Absolute, No Null)

        Usage(Barrel Switch)
        Usage(Secondary Barrel Switch)
        Usage(Tip Switch)
        Usage(Invert)
        Logical Maximum(1)
        Report Count(4)
        Report Size(1)
        Input(Data, Variable, Absolute, No Null)

        Usage(Transducer Serial Number)
        Report Count(1)
        Report Size(128)
        Feature(Constant, Variable)
    EndCollection
EndCollection

unsigned char HID_DESC[] = {
    0x05, 0x0D, // UsagePage(Digitizer)
    0x09, 0x02, // Usage(Pen)
    0xA1, 0x01, // Collection(Application)
    0x09, 0x20, // Usage(Stylus)
    0xA1, 0x02, // Collection(Logical)
    0x09, 0x30, // Usage(Tip Pressure)
    0x15, 0x00, // Logical Minimum(0)
    0x26, 0xFF, 0x03, // Logical Maximum(1023)
    0x95, 0x01, // Report Count(1)
    0x75, 0x0A, // Report Size(10)
    0x81, 0x02, // Input(Data, Variable, Absolute, No Null)

    0x09, 0x44, // Usage(Barrel Switch)
    0x09, 0x5A, // Usage(Secondary Barrel Switch)
    0x09, 0x42, // Usage(Tip Switch)
    0x09, 0x3C, // Usage(Invert)
    0x25, 0x01, // Logical Maximum(1)
    0x95, 0x04, // Report Count(4)
    0x75, 0x01, // Report Size(1)
    0x81, 0x02, // Input(Data, Variable, Absolute, No Null)

    0x09, 0x5B, // Usage(Transducer Serial Number)
    0x95, 0x01, // Report Count(1)
    0x75, 0x80, // Report Size(128)
    0xB1, 0x03, // Feature(Constant, Variable)
    0xC0, // End Collection
    0xC0, // End Collection
}

Guidelines for stylus application developers

The Android 6.0 platform automatically handles pairing and event correlation, so both existing and new applications running on Android 6.0 support Bluetooth stylus by default. For details on Bluetooth stylus APIs, refer to developer.android.com.