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SC400 Controller Communications
Command
Unit Type
Calibrate 3 Point
Syntax:
<SOH>C3<CR>
Response:
<SOH>0<CR>
<SOH>1<CR>
A valid touch coordinate (point) response ('1') signifies that a touch coordinate was
detected and is in range of the expected screen target area. Three valid point responses
indicate successful calibration.
<SOH>0<CR>
An invalid touch coordinate (point) response ('0') is returned if the touch coordinate is
out of range. If either calibration point is invalid, the touch coordinates are discarded and
the calibration points remain unchanged from their previous values. If you receive a
negative response, you must start over again.
<SOH>2<CR>
An invalid touch coordinate (point) response ('2') is returned if the user did not touch the
target long enough to provide an accurate calibration point.
Description:
Initiates an interactive 3-point calibration.
In addition to scaling the Format Tablet output to the display, this command corrects for
touch screen display orientation and touch screen pinout variations. This information will
be maintained by the controller. The Calibrate 3 Point command initiates an interactive
calibration procedure which defines the active area of the touch screen by mapping
locations to an absolute X,Y coordinate system. Touch points generated subsequent to a
successful calibration operation are calculated based upon these calibration points.
Calibrate 3 Point utilizes inset calibration points located 12½ percent inboard from the
screen corners (at touch X,Y locations 128,128, 895,895 and 128,895) for accuracy and
ease of operation.
Guidelines for the C3 Commands
Here are several guidelines for using the C3 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. 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 area changes physical size.
•
You can restart calibration at any time during this sequence by issuing a Reset command and
reissuing a C3 command.
Code
Description
UT
Returns controller unit type string and status.
Positive response to initializing the command.
Positive touch response.
Negative touch response.
Negative touch response.
3M Touch Systems Proprietary Information
19
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