2011年5月20日 星期五

HID report descriptor


The Items on report descriptor is classified into three categories.
Main Items:
- Input
- Output
- Feature
- Collection
- End Collection
Global Items:
- Usage Page
- Logical Minimum / Logical Maximum
- Physical Minimum / Physical Maximum
- Report Size
- Report Count
- Report ID
- Unit
- Unit Exponent
- Push / Pop
Local Items:
- Usage, Usage Minimun / Usage Maximum
- Designator Index, Designator Minimum / Designator Maximum
- String Index, String Minimum / String Maximum
- Delimiter
- Reserved

Global and Local items describe the details of the format
Main Item (Input, Output, Feature) generates report field(s) of specified type, detailed by global and local items.
Collection / End Collection pair defines a block of report fields - which may be nested
The value of each global item is carried over to all of following lines, until new value is defined.
On the other hand, value of local item is cleared, when it is applied to a major item.
This table illustrates the difference of global and local items.



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