Carrol Touch Modular Flat Panel Specifications download pdf (Page 227)

Appendix D - CTKERN Function Reference CARROLL TOUCH

D-32 Touch System Programmer’s Guide

The absolute pixel value is derived by taking a percentage of either the

scaled or raw touch coordinate range, depending on whether scaling is

enabled.

Figure D-1 pictures an example of a spatial filter box set to 25%. Note

that this is a much larger value than is usually used - this value is usually

less than 10%.

Figure D-1. Temporal Filter Spatial Box Size

This approach ensures that the spatial filter box size remains constant

for a given monitor. However, if a touch application that uses the

temporal filter is run on several monitors of differing sizes, the absolute

size of the spatial filter box will vary and may need to be adjusted.

The Temporal Filter Time is specified in milliseconds. The valid range

for this parameter is between 0 ms and 2000 ms, and the default is 500

ms. The actual filter time that is used, however, is restricted to multiples

of 55 ms. The actual formula used is as follows:

absolute time = Trunc (specified filter time / 55) * 55

For example, if you specify a time of 50, the time value used is actually

set to 0. If you specified a value of 100, the time value is 55. If you

specified a value of 500, the time value is 495. The filter time resolution

is 55 ms, which means that the actual amount of time that is required to

trigger a touch may vary from the actual filter time by +/- 55 ms.

box size

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Carrol Touch Modular Flat Panel Specifications Page 227