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59 <strong>HID</strong> <strong>Sensor</strong> <strong>Usage</strong>s<br />
Strategy 1: nesting<br />
A single Top Level Collection can be<br />
defined, where the <strong>Sensor</strong> logical<br />
devices are incorporated as nested sub-<br />
Collections.<br />
The implications of this approach are<br />
that a single device driver will be<br />
loaded for the single Top Level<br />
Collection, and that device driver must<br />
parse the sub-Collections to determine<br />
how to communicate with the<br />
individual <strong>Sensor</strong> logical devices.<br />
Strategy 2: no nesting<br />
Multiple Top Level Collections can be<br />
defined, one per <strong>Sensor</strong> logical device.<br />
The implications of this approach are<br />
that a device driver must be loaded for<br />
each of the individual Top Level<br />
Collections.<br />
They could be completely separate<br />
device drivers, one per <strong>Sensor</strong> logical<br />
device, or they could be multiple<br />
instances of the same device driver that<br />
is able to communicate with sensors of<br />
different types.<br />
<strong>Usage</strong> Page (<strong>Sensor</strong>s)<br />
<strong>Usage</strong> (<strong>Sensor</strong>)<br />
Collection (Application)<br />
<strong>Usage</strong> (Accelerometer)<br />
Collection (Physical)<br />
…<br />
End Collection<br />
<strong>Usage</strong> (Compass)<br />
Collection (Physical)<br />
…<br />
End Collection<br />
<strong>Usage</strong> (Gyro)<br />
Collection (Physical)<br />
…<br />
End Collection<br />
End Collection<br />
Figure 5. One TLC, 3 sub-Collections<br />
<strong>Usage</strong> Page (<strong>Sensor</strong>s)<br />
<strong>Usage</strong> (Accelerometer)<br />
Collection (Application)<br />
…<br />
End Collection<br />
<strong>Usage</strong> (Compass)<br />
Collection (Application)<br />
…<br />
End Collection<br />
<strong>Usage</strong> (Gyro)<br />
Collection (Application)<br />
…<br />
End Collection<br />
Figure 6. Three TLCs<br />
See Also<br />
For full examples of <strong>HID</strong> Report Descriptors illustrating multiple <strong>HID</strong> sensor logical devices; please refer<br />
to Section 4.2.5, below.
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