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Appendix D - CTKERN Function Reference CARROLL TOUCH
D-34 Touch System Programmer’s Guide
SetTemporalFilterParameters (15)
Description
This function sets the temporal filter parameters.
Call with
AL
= 15 (function number).
CL
= Spatial filter box size.
DX
= Temporal filter time.
Returns
AL
= Temporal filter status.
00 = Temporal filter parameters valid.
01 = Spatial filter box size out of range.
02 = Temporal filter time out of range.
Notes
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.
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.
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: