EX II 3000SP Controller Communications

23

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.

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