Datasheet

881
SAM9G15 [DATASHEET]
11052D–ATARM–31-Oct-12
Figure 41-6. Touchscreen Switches Implementation
41.7.4 4-wire Pressure Measurement Method
The method to measure the pressure (Rp) applied to the touchscreen is based on the known resistance of the X-Panel
resistance (Rxp).
Three conversions (Xpos, Z1, Z2) are necessary to determine the value of Rp (Zaxis resistance).
Rp = Rxp*(Xpos/1024)*[(Z2/Z1)-1]
X
P
X
M
Y
M
VDDANA
Y
P
VDDANA
GND
GND
To the ADC
X
P
X
M
Y
P
VDDANA
GND
Switch
Resistor
Switch
Resistor
Y
P
Y
M
X
P
VDDANA
GND
Switch
Resistor
Switch
Resistor
Horizontal Position Detection
Vertical Position Detection
0
1
2
3