CRTOUCH Datasheet, PDF (16/68 Pages) Freescale Semiconductor, Inc – Capacitive and Resistive Touch Sensing Application Specific IC.

Functional Description
threshold is set to one tenth of the resolution; a value of one would mean one unit of the resolution, which cannot produce a
slide because no motion may have a distance greater than the resolution.
The Slide Displacement register reports the accumulated steps of the motion after it begins, therefore each time the threshold is
crossed, this value is incremented. This value is reset if a change of direction is detected or when the screen is touched after a
release.
2.1.6.2 Two touch gestures
The CRTouch device is capable of detecting when two independent touches are present in the screen and when Zoom and Rotate
gestures are performed by these two touches. Two touch detection is enabled when either Zoom or Rotate are enabled in the
Configuration register. When two touches are detected, the Two Touch bit in the Status register 1 is set. In this state, coordinates
reported in the X and Y registers should be disregarded by the display controller. When detecting a two touch event, the
CRTouch continuously measures displacement of the fingers. This displacement may reflect in terms of the distance between
the fingers (Zoom gesture), the slope of the line between the fingers (Rotate gesture), or both.
For two touch gestures to operate, it is mandatory to run the calibration process described in section Section 2.1.4, “Calibration
process.” Two touch gestures and display resolution must be configured before running the calibration to properly calibrate the
gesture detection. For two touch gestures, the CRTouch uses internally a different resolution for the distances between the
fingers in each axis. The smaller axis has a fixed resolution of 1000, while the other axis resolution is calculated to match the
screen proportions. For a screen with 16:9 proportions, for example, one axis would have a resolution of 1000 and the other of
1777. The screen proportion is calculated according to the Vertical Resolution and Horizontal Resolution values. These values
are used to calculate the distance between the fingers.
TwoTouchResolutionA = 1000
TwoTouchResolutionB
=
1000 
H_-----o_----r_--i_--z_---o_---n_----t_--a_---l_--R_----e_---s_---o_---l_--u_----t_--i_--o_---n_-
VerticalResolution
or
Whichever is the highest.
TwoTouchResolutionB = 1000  ----^V----^e---^r---^t--ⁱ--^c---^a---^l--^R----^e---^s---^o----^l--^u---^t--ⁱ--^o---ⁿ-----
HorizontalResolution
Eqn. 1
Eqn. 2
Eqn. 3
MaxTwoTouchDis tan ce = ResolutionA ² + ResolutionB²
Eqn. 4
The signals required for two touch detection are obtained through the resistors connected to the Xr and Yr signal. Unexpected
behaviors may be produced if these resistors are not connected and two touch gestures are enabled.
2.1.6.3 Zoom gesture
When the distance between the fingers varies, a zoom gesture is detected. If the distance increases, a zoom-in direction is
reported through the RTSZD bit in the Status Register 2. If the distance decreases, a zoom-out direction is reported through the
RTSZD bit in the Status Register 2. In either case, the RTSZ bit is set in Status Register 1. Similar to the slide gesture, the zoom
gesture is reported when a threshold is crossed. This threshold is approximately one tenth of the smaller axis of the screen. The
Zoom Size register is updated each time the threshold is crossed and is cumulative throughout the gesture. The value of this
register is equal to one tenth of the distance displacement.
ZoomSize = --^I--ⁿ----ⁱ--^t--^D----ⁱ--^s---t--a---n---^c---^e-----–--1--^A-0---^c---^t--^u----^a---^l--^D-----ⁱ--^s---t-a---n----^c---^e--
Eqn. 5
CRTouch Data Sheet, Rev. 3
16
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