You also want an ePaper? Increase the reach of your titles
YUMPU automatically turns print PDFs into web optimized ePapers that Google loves.
64 <strong>HID</strong> <strong>Sensor</strong> <strong>Usage</strong>s<br />
All the Properties are packed as Items into a single Feature Report.<br />
It should be appreciated by the reader that:<br />
A device with multiple sensors will be forced to use separate Report IDs to disambiguate the<br />
Reports (see Section 4.2.5 “<strong>Sensor</strong> Collections” below for an example of this);<br />
Even a device with a single sensor may use separate Report IDs for the Data Fields and<br />
Properties, as needed due to the size of the data to be transferred.<br />
3.7 <strong>HID</strong> <strong>Usage</strong>s<br />
<strong>HID</strong> Collections and <strong>HID</strong> Report Items can be described by a number of different characteristics. These<br />
characteristics are described in the <strong>HID</strong> Report Descriptor. One of the most important of these is the<br />
<strong>Usage</strong>. The <strong>HID</strong> <strong>Usage</strong> tells what a given Collection or Report Item means (its semantics).<br />
See Also<br />
For: The <strong>HID</strong> <strong>Usage</strong> appears: And it tells:<br />
Collections Before the<br />
Collection(Application)<br />
or Collection(Physical)<br />
descriptor item.<br />
Report Items Before the Input() or<br />
Feature() descriptor item. 3<br />
What sensor Type the Collection<br />
describes.<br />
What sensor Property or Data<br />
Field the Report Item describes.<br />
Table 14. <strong>Usage</strong>s applied to Collections and Report Items<br />
For more information about <strong>HID</strong> <strong>Usage</strong>s; please refer to the <strong>USB</strong> <strong>HID</strong> <strong>Usage</strong> <strong>Tables</strong> specification<br />
(Reference Document [3]).<br />
For sensor-specific <strong>HID</strong> <strong>Usage</strong>s; please refer to Section 1 <strong>Sensor</strong> <strong>Usage</strong>s, above.<br />
3.7.1 <strong>HID</strong> <strong>Usage</strong> Types<br />
There are different varieties of usages when applied to Collections or Report Items. This is called the<br />
<strong>Usage</strong> Type, as listed in the following table:<br />
<strong>Usage</strong> Type Descriptor item flags Description of <strong>HID</strong> use <strong>Sensor</strong>-related use<br />
CA<br />
Application Top level collection<br />
CP Collection Physical Nested collection <strong>Sensor</strong> object (Category or Type)<br />
CL Logical Nested collection<br />
US <strong>Usage</strong> N/A Modifies a <strong>Usage</strong> Data Field modifiers and threshold<br />
Switch<br />
Properties<br />
SF Static Constant, Variable, A read-only single bit Boolean Data Field or read-only<br />
Flag Absolute<br />
value<br />
Property<br />
SV Static Constant, Variable, A read-only multi-bit Other typed Data Field or read-only<br />
Value Absolute<br />
value<br />
Property<br />
3 According to the <strong>USB</strong> <strong>HID</strong> <strong>Usage</strong> <strong>Tables</strong> specification (Reference Document [3]), a <strong>Usage</strong> may also be<br />
employed to describe an Output() descriptor item. But because Output() descriptor items are not<br />
defined for the <strong>HID</strong> <strong>Sensor</strong> <strong>Usage</strong> Page, it was not mentioned in the table.
Change language