Cirrus Logic EP93xx - Manual (Page 740)

25-2 DS785UM1
Copyright 2007 Cirrus Logic
Analog Touch Screen Interface
EP93xx User’s Guide
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5
2
5
25
Figure 25-1. Different Types of Touch Screens
For 8- and 4-wire touch screens, the point at which the contact is made can be determined by
measuring a voltage driven between the bus bars on the X-axis layer through either or both of
the Y lines, and by then measuring a voltage driven between the bus bars on the Y-axis layer
through either or both of the X lines. By comparing these voltages to values determined
during calibration, the location of the touch can be determined.
4 WIRE ANALOG RESISTIVE TOUCH SCREEN SCHEMATIC
X+
Y+
X-
Y-
8 WIRE ANALOG RESISTIVE TOUCH SCREEN SCHEMATIC
X+
Y+
X-
Y-
SX+
SY+
SX-
SY-
5 WIRE ANALOG RESISTIVE TOUCH SCREEN SCHEMATIC
V+
Z+/-
V-
Z-/+
Wiper
7 WIRE (5 WIRE WITH FEEDBACK) ANALOG RESISTIVE
TOUCH SCREEN SCHEMATIC
V+
Z+/-
V-
Z-/+
sV+
sV-
Wiper