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EX II 3000SP Controller Communications 23
3M Touch Systems Proprietary Information
Calibrate Extended
Syntax: <SOH>CX<CR>
Description: Initiates an interactive, two-point calibration.
During the calibration process, you define the active area of the touch
screen by mapping locations to an absolute X/Y coordinate system. You
touch two target areas on the screen. Touching the target areas sends the
X/Y coordinates for those touch points to the controller. The controller
calculates all other touch points based on these two points.
The Calibrate Extended command sets the calibration targets (points)
inward from the corner of the video image. Setting the targets inward makes
the calibration process easier and more accurate.
Guidelines for Calibrate Extended
Here are several guidelines for using the Calibrate Extended command:
• The controller uses the data immediately before liftoff to register a calibration
touch. Therefore, users can touch the screen, move their finger to the target,
hold for one second, and then lift off their finger. Instructing users to touch this
way results in a more accurate calibration.
• The controller stores the data in non-volatile memory (NOVRAM). Therefore,
you do not have to calibrate the screen each time you power on the system. You
should, however, recalibrate the touch screen any time the video display
changes size or resolution or gets repositioned.
• You can restart calibration at any time during this sequence by issuing a Reset
command and reissuing a CX command.
Determining Target Areas
The default calibration targets (points) are located 12.5% (1/8) inward from
the corners of the video image. For example, suppose the display resolution
of your monitor is 1024 x 768. The Calibrate Extended command calculates
the amount to move inward as follows:
•
Amount to move inward in the X direction: 1024 x 1/8 = 128
• Amount to move inward in the Y direction: 768 x 1/8 = 96
The Calibrate Extended command then positions the first calibration target
inward from the lower left corner (0,767) and the second calibration target
inward from the upper right corner (1023,0). The following illustration
shows how the calibration targets are calculated.