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3M™ Multi-Touch Desktop Display User Guide
3M Touch Systems, Inc. Proprietary Information – TSD-40532C
Table 2. Calibration Setup Stage
Offset
Field
Size
Value
Description
0 bmRequestType
1
0x21
Class,H2D,Interface
1 bRequest 1
0x09
Set
Report
2
wValue
2
0x0303
Msb 03 = Feature
Lsb 03 = Feature Report ID
4 wIndex
2
0 Always
0
6 wLength 2
8 Always
8
Table 3. Data Stage
Offset
Field
Size
Value
Description
0
Report ID
1
0x03
Feature report ID
1
Report Subtype
1
0x04
Indicates a calibration request
2
bCalType
1
0x01
0x01 = Extended cal (CX)
3--7
Not used
5
0
Not used
The device stalls endpoint 0 if the command cannot be processed successfully. The
request cannot be processed if an invalid calibration type is given in the wValue field.
The request will also fail if the 2 calibration points do not fall within certain bounds
established by the firmware. These bounds require that the 2 calibration points be in
opposite quadrants of the sensor.
The host should issue a GetStatus request to determine the status of this request. The
status report includes a command status byte which will be set as shown below.
Table 4. Calibration Response
Command Status Byte
Description
0 Calibration
Failed
1
Controller is waiting for a touch in the lower left corner.
Calibration software paints a target in the lower left corner.
2
Controller is waiting for a touch in the upper right corner.
Calibration software paints a target in the upper right corner.
3
Calibration completed successfully.
The controller does not timeout waiting for touch. Use the soft reset command to abort
the calibration.
Determining Target Areas
The default calibration targets (points) are located 12.5% (1/8) inward from the corners of
the video image. For example, if the resolution of your Windows-based display is 1920 x
1080, the Calibrate Extended command calculates the amount to move inward as follows:
•
Amount to move inward in the X direction: 1920 x 1/8 = 240
•
Amount to move inward in the Y direction: 1080 x 1/8 = 135
