AT32UC3L064-D3HES ATMEL [ATMEL Corporation], AT32UC3L064-D3HES Datasheet - Page 604

• Manufacturer Part Number: AT32UC3L064-D3HES
• Manufacturer: ATMEL [ATMEL Corporation]

26.7
26.7.1
26.7.2
32099D–06/2010
Resistive Touch Screen
Resistive Touch Screen Principles
Position Measurement Method
The ADCIFB embeds an integrated resistive touch screen sequencer that can be used to calcu-
late contact coordinates on a resistive film touch screen. When instructed to start, the integrated
touch screen sequencer automatically applies a sequence of voltage patterns to the touch
screen films and the Analog-to-Digital Conversion cell is used to measure the effects. The result-
ing measurements can be used to calculate the horizontal and vertical contact coordinates. It is
recommended to use a high resistance touch screen for optimal resolution.
The touch screen film is connected to the ADCIFB using the AD and ADP pins. See
26.7.3
Touch Screen ADC Mode is enabled by writing a one to the TSAMOD field in the Mode Register
(MR). In this mode, channels TSPO+0 though TSPO+3 are automatically enabled where TSPO
refers to the Touch Screen Pin Offset field in the Mode Register. For each conversion sequence,
all enabled channels before TSPO+0 and after TSPO+3 are converted as ordinary ADC chan-
nels, producing 1 conversion result each. When the sequencer enters the TSPO+0 channel the
touch screen sequencer will take over control and convert the next 4 channels as described in
Section
A resistive touch screen is based on two resistive films, each one fitted with a pair of electrodes,
placed at the top and bottom on one film, and on the right and left on the other. Between the two,
there is a layer that acts as an insulator, but makes a connection when pressure is applied to the
screen. This is illustrated in
Figure 26-2. Touch Screen Position Measurement
As shown in
to X
P
(top) and X
for details.
26.7.4.
Figure 26-2 on page
Vertical Position Detection
X
m
X
M
P
(bottom) leaving Y
Y
M
Y
P
Figure 26-2 on page
Volt
VDD
GND
604, to detect the position of a contact, voltage is first applied
X
p
M
and Y
Contact
Pen
m
tristated. Due to the linear resistance of the film,
604.
X
AT32UC3L016/32/64
P
Horizontal Position Detection
Y
Y
M
P
Y
P
X
P
Volt
VDD
GND
Section
604