CRTOUCH Datasheet, PDF (9/68 Pages) Freescale Semiconductor, Inc – Capacitive and Resistive Touch Sensing Application Specific IC.

X stabilization Y stabilization
X
Y
Functional Description
X
Sampling period
Scanning Process for X and Y coordinates only
X stabilization Y stabilization
Z stabilization
X
Y1 Y2
Z1 Z2
X
Sampling period
Scanning Process for X ,Y, and Pressure
X stabilization Y stabilization
Z stabilization
X stabilization Y stabilization
X
Y1 Y2
Z1 Z2
Xr
Yr
X
Sampling period
Figure 6. Scanning process for X, Y, pressure, and two touch gestures
As seen in the previous figure, the scanning sequence repeats at a fixed period of time. This period is configurable in the
Sampling Time register and may be in the range of 5 ms to 100 ms. The CRTouch scans the screen signals only when a touch
is detected. When the screen is not touched, the device stays in a standby state.
At the end of the scanning process, a set of coordinates is produced. These coordinates have a default resolution of 12 bits, or
4096 points per axis. However, this resolution may be modified to reflect the proportions of the screen more accurately (typical
screens have a 4:3 or 16:9 proportion). This can be done by writing to the horizontal resolution and vertical resolution, which
correspond to the X and Y resolution respectively. The resulting X and Y values are scaled to fit into this resolution.
The CRTouch is capable of autodetecting the type of the screen connected. The type of screen detected is reflected in the Status
Register 2. Only two touch gestures and pressure detection is available for 4 wire screens, and cannot be enabled when a 5 wire
screen is connected.
CRTouch Data Sheet, Rev. 3
Freescale Semiconductor
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