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User Manual 190S6FGT
5
1
9
6
Front view
13.2
THE WORKING PRINCIPLE OF 5 WIRE
RESISTIVE TOUCH SCREEN
The Structure of Touch screen The 5 wire resistive touch screen uses a
glass panel with a uniform conductive ITO (indium tin oxide) coating on
the one-side surface. A PET film is tightly suspended over the ITO
coating surface of a glass panel. The glass substrate and the PET film are
separated by tiny, transparent insulating dot spacers. The PET film has a
hard coating on the outer side and a conductive ITO coating on the
inner side.
Working Principle
1 When the screen is touched, it pushes the conductive ITO coating
on the PET film against the ITO coating on the glass. That results in
an electrical contact, producing the voltages. It presents the position
touched.
2 When the controller is waiting for a touch, the resistive layer of the
touch screen is biased at +5V through the four drive lines, and the
PET film is grounded through a high resistance. When the touch
screen is not touched, the voltage on the PET film is zero.
The voltage of the PET film is continuously converted by the A/D
(analog-to-digital ) converter and monitored by the microprocessor
on the controller.
3 When the touch screen is touched, the microprocessor detects the
voltage of the PET film and begins generating the (X,Y) coordinates.
The microprocessor applies +5V to pins X and H on the X drive
●
of the touch screen ,and grounds pins Y and L. A voltage
proportional to the X (horizontal) position of the touch appears
on the PET film at pin S of the touch screen connector.
This voltage is digitized by the A/D Converter and subjected to
an averaging algorithm. Then it is stored and transferred to the
host. Hence, the X position is produced.
Secondly, the microprocessor applies +5V to pins Y and L on the
●
Y drive of the touch screen, and ground pins X and H. A voltage
proportional to the Y (vertical) position of the touch appears on
the PET film at pin S of the touch screen connector. This signal is
converted, and the Y position is produced.
Pin Assignments
Control board
Clear To Send (CTS)
1
Receive Data (RXD)
2
Transmit Data (TXD)
3
VCC
4
Signal Ground (GND)
5
Data Set Ready (DSR)
6
Data Carrier Detect (DCD)
7
NC
8
NC
9
48
RS 232 port
7
2
3
4
5
6
1
8
9
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