AT32UC3L0256 Atmel Corporation, AT32UC3L0256 Datasheet - Page 612

• Manufacturer Part Number: AT32UC3L0256
• Manufacturer: Atmel Corporation

Specifications of AT32UC3L0256

• Flash (kbytes): 256 Kbytes
• Pin Count: 48
• Max. Operating Frequency: 50 MHz
• Cpu: 32-bit AVR
• # Of Touch Channels: 17
• Hardware Qtouch Acquisition: Yes
• Max I/o Pins: 36
• Ext Interrupts: 36
• Usb Speed: No
• Usb Interface: No
• Spi: 5
• Twi (i2c): 2
• Uart: 4
• Lin: 4
• Graphic Lcd: No
• Video Decoder: No
• Camera Interface: No
• Adc Channels: 8
• Adc Resolution (bits): 12
• Adc Speed (ksps): 460
• Analog Comparators: 8
• Resistive Touch Screen: No
• Temp. Sensor: Yes
• Crypto Engine: No
• Sram (kbytes): 16
• Self Program Memory: YES
• Dram Memory: No
• Nand Interface: No
• Picopower: Yes
• Temp. Range (deg C): -40 to 85
• I/o Supply Class: 1.62 to 3.6
• Operating Voltage (vcc): 1.62 to 3.6
• Fpu: No
• Mpu / Mmu: Yes / No
• Timers: 6
• Output Compare Channels: 18
• Input Capture Channels: 12
• Pwm Channels: 35
• 32khz Rtc: Yes
• Calibrated Rc Oscillator: Yes

26.7.1
26.7.2
32145A–12/2011
Resistive Touch Screen Principles
Position Measurement Method
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. Resistive Touch Screen Position Measurement
As shown in
to X
there is a voltage gradient from top to bottom on the first film. When a contact is performed on
the screen, the voltage at the contact point propagates to the second film. If the input impedance
on the Y
age at the contact point to be measured at Y
position component of the contact point.
For the horizontal direction, the same method is used, but by applying voltage from Y
Y
In an ideal world (linear, with no loss), the vertical position is equal to:
To compensate for some of the real world imperfections, VX
used to improve accuracy at the cost of two more conversions per axes. The new expression for
the vertical position then becomes:
m
(left) and measuring at X
P
(top) and X
VY
(VY
P
P
P
(right) and Y
/ VDD
- VX
Figure 26-2 on page
Vertical Position Detection
M
X
m
X
) / (VX
M
P
(bottom) leaving Y
m
P
Y
(left) electrodes are high enough, no current will flow, allowing the volt-
M
- VX
Y
P
Figure 26-2 on page
P
.
M
)
Volt
VDD
GND
612, 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,
p
. The value measured represents the vertical
612.
X
P
Horizontal Position Detection
AT32UC3L0128/256
Y
P
Y
M
P
and VX
Y
P
m
X
P
can be measured and
Volt
VDD
GND
P
(right) to
612