HID Sensor Usage Tables - USB.org

65 HID Sensor Usages
DF Dynamic Data, Variable, A read/write single bit Boolean read/write Property
Flag Absolute
value
DV Dynamic Data, Variable, A read/write multi-bit Other typed read/write Property
Value Absolute
value
NAry Named Constant, Array, An enumerated value Enumerated-value Data Field or
Array Absolute or Data,
Array, Absolute
Property
Sel Selection N/A One of the selection One of the selections for the enumerated-
choices for a Named
Array
value of a Data Field or Property
Table 15. HID Usage Types
These Usage Types appear in the listed Sensor Usage Page (see Section 1, above). They give some
information about how the different types of Usages should be employed.
See Also
For more information about HID Usage Types; please refer to Section 3.4.2, 3.4.3 of the USB HID Usage
Tables specification (Reference Document [3]).
3.7.2 HID Selectors
One particularly interesting Usage Type is the Selector (marked as “Sel” in the tables) and its parent, the
Named Array (marked as “NAry” in the tables).
For those familiar with high-level programming languages such as C++, the Named Array is analogous to a
variable with an enumeration type; the Selectors are analogous to the various enumeration constants that
the variable may take on.
One aspect that is unique about HID Selectors is that the actual numeric values of the Report Items that are
passed in the HID Reports depend upon both the order in which the Selectors are declared, and interaction
with the Logical Minimum and Logical Maximum declarations. Here is an example for the Sensor State
Usage:
.
.
.
HID_LOGICAL_MIN_8(0), // lowest numerical value of this enumeration will be 0
HID_LOGICAL_MAX_8(6), // highest numerical value of this enumeration will be 6
HID_REPORT_SIZE(8), // Input Report Item will be 8 bits long
HID_REPORT_COUNT(1), // and there are 1 of them
HID_USAGE_SENSOR_STATE, // NAry – the Current Sensor State reported as Data Field in Input Report
HID_COLLECTION(Logical),
HID_USAGE_SENSOR_STATE_UNKNOWN, // Sel - this will take on value 0
HID_USAGE_SENSOR_STATE_READY, // Sel - this will take on value 1
HID_USAGE_SENSOR_STATE_NOT_AVAILABLE, // Sel - this will take on value 2
HID_USAGE_SENSOR_STATE_NO_DATA, // Sel - this will take on value 3
HID_USAGE_SENSOR_STATE_INITIALIZING, // Sel - this will take on value 4
HID_USAGE_SENSOR_STATE_ACCESS_DENIED, // Sel - this will take on value 5
HID_USAGE_SENSOR_STATE_ERROR, // Sel - this will take on value 6
HID_INPUT(Const_Arr_Abs), // Input Item – takes on characteristics previously declared
HID_END_COLLECTION,
.
.
.
Note that for maximum interoperability of implementations, the following assumptions and restrictions are
in force for sensors:
The Named Array Usage is applied to a Logical Collection.
All the defined Selectors for each Named Array must be declared (don’t omit any);
Always start the Logical Minimum at zero;