3M Systems EX II 3700SP - Manual (Page 18)

18 3M™ MicroTouch™ Controller SX112 Reference Guide
3M Touch Systems, Inc. Proprietary Information
Calibrate Extended
Syntax: <SOH>CX<CR>
Note: This command should not be used when 3M™ MicroTouch™ Software is being
used. The CX command will interfere with the auto orientation algorithm. To calibrate,
use the 2- or 4-point calibration in 3M™ MicroTouch™ Software.
Description: Initiates an interactive 2-point calibration.
During the calibration process, you define the active area of the sensor by mapping
locations to an absolute X/Y coordinate system. You touch two target areas on the
sensor. 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, you can touch the sensor, move your finger to the target, hold for a few
seconds, and then lift off. 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 sensor each time you power on the system. You should,
however, recalibrate the sensor any time the video display changes size or resolution.
• 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 display 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 and the second calibration target inward from the upper right corner.
The following illustration shows how the calibration targets are calculated.