3M M2256PW manual Guidelines for Calibrate Command, Calibrate Procedure, Determining Target Areas

34 3M™ Multi-touch Display M2256PW User Guide

Calibrate Procedure

To use the CX command:

1.Enter the Calibrate (CX) command. The controller sends an initial acknowledgment of <SOH>0<CR>.

2.Touch the sensor at a lower left target, which is located 12.5% (1/8) in from the corner of the video image. The controller returns an acknowledgment of <SOH>1<CR>. This is a positive response. If you receive a negative response <SOH>0<CR>, you can cancel the calibration by issuing a Reset command and then start over again.

3.Touch the sensor at an upper right target, which is located 12.5% (1/8) in from the corner of the video image. The controller returns an acknowledgment of <SOH>1<CR>. This is a positive response. If you receive a negative response, you must start over again.

Touching the two valid calibration points results in a successful calibration. If either calibration point is invalid, the calibration fails. The PX controller restores the previous calibration values. If Calibrate fails, repeat the CX process.

Guidelines for Calibrate Command

Here are several guidelines for using the Calibrate commands:

•The controller uses the data immediately before liftoff to register a calibration touch. Therefore, you can touch the coordinate 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 touch sensor any time the video display changes size or resolution.

•You can cancel calibration at any time during this sequence by issuing a Reset 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, the resolution of your Windows-based display is 1680 x 1050. The Calibrate Extended command calculates the amount to move inward as follows:

•Amount to move inward in the X direction: 1680 x 1/8 = 210

•Amount to move inward in the Y direction: 1050 x 1/8 = 131

The Calibrate Extended command then positions the first calibration target inward from the lower left corner (0,1049) and the second calibration target inward from the upper right corner (1679,0). The following illustration shows how the calibration targets are calculated for a Windows-based system. Your operating system may be different.

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