Usages

USB HID devices and their components can be given a Usage code. The Usage code is an optional suggestion to the application on what the control is to be used for.

A usage code is broken up into two parts: the Usage Page and the Usage. Both are 16-bit numbers (0-65535). Any values can be used, but there are a set of defined values.

The Usage Page is used to group usages. A set of Usage Pages has been defined by the USB group. These are listed below...

GENERIC_DESKTOP_CONTROLS	0x01
SIMULATION_CONTROLS	0x02
VR_CONTROLS	0x03
SPORT_CONTROLS	0x04
GAME_CONTROLS	0x05
GENERIC_DEVICE_CONTROLS	0x06
KEYBOARD_KEYPAD	0x07
LEDS	0x08
BUTTON	0x09
ORDINAL	0x0A
TELEPHONY	0x0B
CONSUMER	0x0C
DIGITIZER	0x0D
PID_PAGE	0x0F
UNICODE	0x10
ALPHANUMERIC_DISPLAY	0x14
MEDICAL_INSTRUMENTS	0x40
MONITOR_PAGES	0x83
POWER_PAGES	0x87
BAR_CODE_SCANNER_PAGE	0x8C
SCALE_PAGE	0x8D
MAGNETIC_STRIPE_READING_DEVICES	0x8E
CAMERA_CONTROL_PAGE	0x90
ARCADE_PAGE	0x91
VENDOR_DEFINED	0xFF00

Each Usage Page has a collection of Usages. For example, these are Usages for the Usage Page GENERIC_DESKTOP_CONTROLS.

POINTER	0x01
MOUSE	0x02
JOYSTICK	0x04
GAME PAD	0x05
KEYBOARD	0x06
KEYPAD	0x07
X	0x30
Y	0x31
Z	0x32
RX	0x33
RY	0x34
RZ	0x35
SLIDER	0x36
DIAL	0x37
WHEEL	0x38
HATSWITCH	0x39
START	0x3D
SELECT	0x3E
DPAD_UP	0x90
DPAD_DOWN	0x91
DPAD_RIGHT	0x92
DPAD_LEFT	0x93

Generally, it is not important what the Usage Page and Usage are, however there are some exceptions...

LCD display modules must have a Usage of ALPHANUMERIC_DISPLAY:ALPHANUMERIC_DISPLAY otherwise it will not be identified as a display device. Generic HID will not let this be changed.
A directional switch/hat switch must be called GENERIC_DESKTOP_CONTROLS:HATSWITCH otherwise the values will not be reinterpreted as a directional angle.
To get Windows and other operating systems to recognise the device as a joystick or game pad, it must be called GENERIC_DESKTOP_CONTROLS:JOYSTICK or GENERIC_DESKTOP_CONTROLS:GAMEPAD. Windows will also typically want the usage of an axis set X, Y, Z, etc.
Avoid using GENERIC_DESKTOP_CONTROLS:MOUSE or GENERIC_DESKTOP_CONTROLS:POINTER as the usage for a device. The operating system will take control of the device and interpret actions as mouse moves and button presses.

The property field for the Usage is displayed as the Usage Page and the Usage. These are two drop down lists that contain the standard Usage Pages and Usages as shown below.

It is not necessary to use one of the predefined values. A user defined number may be entered. This is required on some usage pages like LED.