RA8806
Preliminary Version 1.0
Two Layers Character/Graphic LCD Controller
6-4 Touch Panel
RA8806 built in a 10-bit ADC and control circuits to connect with 4-wires resistance type touch panel.
Resistive Touch Panel is composed of two layer extremely thin resistive panel, such as Figure 6-16.
There is a small gap between these two-layer panels. When external force press a certain point, the
two-layer resistive panels will be touched, which is short. Because the end points of two-layer have
electrodes (XL, XR, YU, YD), such as Figure 6-17, a comparative location will be detected with some
switches in coordination.
YU
Y Plate
X Plate
Electrode
XL
XR
YD
Figure 6-16：Touch Panel
VDD
SW2
YU
Resistor -Y
XL
XR
VDD
SW0
SW1
Resistor -X
YD
SW3
GND
Figure 6-17 : Control Switch of Touch Panel
Users only need to connect the touch panel signals -- XL, XR, YU, and YD to RA8806. It will
continuously monitor the panel and wait for touch event. When the event is occurred, a divided voltage
on panel caused by touch is sensed and transferred by ADC to determine the location. After the value of
X-axis and Y-axis are transferred and stored in corresponding registers respectively, the touch panel
controller will issue an interrupt to inform MPU to process it.
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