Specifications

60 Chapter 5 - Software Interface

Example2 - Calibrate and Finger Paint

EXAMPLE2.C also polls Elo SmartSet touchscreen controllers. The controller is

first set up for calibration by changing the Mode to report raw coordinates. The

calibration screen appears as follows:

XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX

X X

X * X

X X

X Touch the following points from a X

X position of normal use, e.g. a sitting X

X person of average height and reach. X

X You will hear a beep after each touch. X

X X

XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX

Figure 5-5. EXAMPLE2.C Calibration Screen

A three-point calibration sequence is used. The touch points are taken near the

corners of the screen image, then extrapolated to the actual edges of the image.

This reduces the effects on calibration of "pin cushion" and other non-linearities at

the edges of the image. The calibration sequence causes the origin to be in the

upper-left, regardless of the orientation of the touchscreen. Untouch coordinates

are used in the calibration, so the user can carefully position their finger before

release.

The program then displays the results of the calibration, important information if

troubleshooting is necessary:

Calibration points are: 445,3362, 3563,722

Y axis inverted.

Orientation adjusted.

Press a key to proceed to finger painting...

Figure 5-6. EXAMPLE2.C Calibration Results Output

Next, the controller is programmed for 80x25 Scaling and the Mode is set to

Calibration, Scaling, Trim, and Stream. The point of touch can now be mapped to

the display, as in this example: