HID Usage Tables Document 1.1 - C. Scott Ananian

Universal Serial Bus HID Usage Tables 93A.7 Desktop Tablet ExampleThis is the Report descriptor for a typical desktop digitizing tablet. The tablet’s digitizing region is 12inches square, and it reports data in units of .001 inches. It is optionally equipped with any or all of threecordless transducers: a 16-button cursor, a stylus with a tip and a barrel switch, and a stylus with a pressuretransducer.The example digitizer can distinguish between the different cursors, and it sends a report based on the cursorthat last changed state. The ReportID report data entity indicates which cursor is generating the currentreport. The X and Y position data and the In Range bit are in the same field for each report type, but thepressure and button data are different for each transducer, with padding in the report where necessary. Thevanilla stylus and puck transducers generate 6-byte reports, whereas the pressure stylus generates a 7-bytereport.The Report descriptor below is structured as an application collection containing three physical collections,one for each supported cursor. The ReportID items precede each cursor collection, which causes a separate,tagged report to be defined for each cursor. The Push and Pop items are used to save and restore the itemstate that defines the X and Y fields. The Report descriptor takes advantage of the fact that the tablet issquare— that is, the physical and logical ranges of X and Y position are identical.;; Example Digitizer Report DescriptorUsage Page(Digitizers),; Application collectionUsage(Digitizer),Collection(Application),ReportID(1),; 2-Button StylusUsage(Puck),Collection(Physical),Usage Page(Generic Desktop),; X and Y PositionUsage(X), Usage(Y),ReportSize(16), ReportCount(2),Logical Minimum(0), Logical Maximum(12000),Physical Minimum(0), Physical Maximum(12),Units(English Linear: Distance),; InchesExponent(0),Push,; Save position item stateInput(Data, Variable, Absolute),Usage Page(Digitizers),Usage(In Range),; In Range bit, switchesUsage(Barrel Switch),Usage(Tip Switch),Logical Minimum(0), Logical Maximum(1),Physical Minimum(0), Physical Maximum(1),Units(None),Report Size(1), Report Count(3),Input(Variable, Absolute),Report Count(1), Report Size(5),Input(Constant),End Collection,Report ID(2),Usage(Stylus),Collection(Physical),Pop,Push,; Padding (5 bits); 16-Button Cursor Tag; Refer to Global items; saved during last Push; Report Count (2)Version 1.1 April 8, 1999