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EX II Serial Controllers Reference Guide
3M Touch Systems Proprietary Information
•
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.
•
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 and the second calibration target inward from the upper right corner.
The following illustration shows how the calibration targets are calculated.
*
The coordinates are in
video
terms, with the origin (0, 0) in the upper left corner of the screen. Examples from the
controller’s
perspective, however, place the origin at the lower left corner of the screen (numbers in brackets). The
controller outputs 0 to 1024 on both axes independent of display screen resolution.
Calibrate Extended Procedure
To use the CX command:
1. Enter the Calibrate Extended (CX) command. The controller sends an initial
acknowledgment of <SOH>0<CR>.
2. Touch the screen 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 Rest command and then
start over again.
Upper Right Calibration Target
X = 1023 – (1024 x 1/8) = 1023 – 128 = 895
Y = 0 + (768 x 1/8) = 0 + 96 = 96
(0, 0)
(0, 767) [0,0]*
(
1023, 0) [1024, 1024]*
(80, 60)
(560, 420)
Lower Left Calibration Target
X = 0 + (1024 x 1/8) = 0 + 128 = 128
Y = 767 - (768 x 1/8) = 767 - 96 = 671
(128, 671)
(895, 96)
[
1024, 0]*
