Carrol Touch Modular Flat Panel Specifications download pdf (Page 226)

CARROLL TOUCH Appendix D - CTKERN Function Reference

Touch System Programmer’s Guide D-31

SetTemporalFilterMode (14)

Description

This function sets the temporal filter mode.

Call with

AL = 14 (function number).

BL = Temporal filter mode.

00 = Temporal filter disabled.

01 = Temporal filter enabled.

Notes

When enabled, the temporal filter acts much like a low pass filter in the

time domain for all touch state transitions. You must specify a Spatial

Filter Box Size and a Temporal Filter Time.

When the stylus touches the screen the center of the spatial filter box is

set to the coordinates where the screen was first touched. The touch

state is set to “touched” and the touch coordinates set to the current

stylus location only after the stylus has remained in the spatial filter box

for the length of time specified by the Temporal Filter Time parameter.

If the stylus moves beyond the spatial filter box, the temporal filter

timer and the center of the spatial filter box are reset. The coordinates

are not updated until the stylus has once again remained in the spatial

filter box for the Temporal Filter Time. The coordinates associated with

the “not touched” state are still the exit point, but the touch state

becomes “not touched” only after the stylus is out of the screen for the

Temporal Filter Time. The touch state is set to “non-contiguous” only

after a non-contiguous stylus has been in the touch screen for the

Temporal Filter Time.

The Spatial Filter Box Size is specified as a percentage of the full screen

size. The valid range for this parameter is from 0% to 100% and the

default is 10%. This parameter specifies the width of the box. The

spatial filter box size is specified as a percentage rather than as an

absolute touch coordinate value because if it were specified as an

absolute value, the absolute size of the spatial filter box would vary if

the display resolution changed as a result of a change in the BIOS video

mode. Note that while the same percentage is used for both the x- and

y-axes, the absolute size of the box is not necessarily square. The box

instead has the same aspect ratio as the display. No correction for

display aspect ratio is performed.

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Carrol Touch Modular Flat Panel Specifications Page 226