AT91SAM9G45-EKES Atmel, AT91SAM9G45-EKES Datasheet - Page 940

• Manufacturer Part Number: AT91SAM9G45-EKES
• Description: KIT EVAL FOR AT91SAM9G45
• Manufacturer: Atmel
• Series: AT91SAM Smart ARMr
• Type: MCUr

Specifications of AT91SAM9G45-EKES

• Contents: Board
• Processor To Be Evaluated: SAM9G45
• Data Bus Width: 32 bit
• Interface Type: I2C, SPI, UART
• Maximum Operating Temperature: + 50 C
• Minimum Operating Temperature: - 10 C
• Operating Supply Voltage: 1.8 V to 3.3 V
• For Use With/related Products: AT91SAM9G45
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: Q4626953

Figure 40-2. Touch Screen Position Measurement
40.7.2
940
AT91SAM9G45
Position Measurement Method
As shown in
bottom. Due to the linear resistance of the film, there is a voltage gradient from top to bottom.
When a contact is performed on the screen, the voltage propagates at the point the two surfaces
come into contact with the second film. If the input impedance on the right and left electrodes
sense is high enough, the film does not affect this voltage, despite its resistive nature.
For the horizontal direction, the same method is used, but by applying supply from left to right.
The range depends on the supply voltage and on the loss in the switches that connect to the top
and bottom electrodes.
In an ideal world (linear, with no loss through switches), the horizontal position is equal to:
The proposed implementation with on-chip power switches is shown in
measurement at the output of the switch compensates for the switches loss.
It is possible to correct for the switch loss by performing the operation:
This requires additional measurements, as shown in
Vertical Position Detection
X
X
M
P
VY
[VY
M
P
Y
/ VDD or VY
- VX
M
Figure
Y
P
M
] / [VX
Volt
VDD
40-2, to detect the position of a contact, a supply is first applied from top to
GND
P
P
X
M
/ VDD.
- VX
Contact
Pen
M
].
X
P
Horizontal Position Detection
Y
Y
M
P
Y
P
Figure
X
P
40-3.
Volt
VDD
GND
Figure
6438F–ATARM–21-Jun-10
40-3. The voltage