Datasheet

935
SAM9G45 [DATASHEET]
Atmel-6438O-ATARM-SAM9G45-Datasheet_08-Dec-15
39.7.3 Pressure Measurement Method
The method to measure the pressure (Rp) applied to the touchscreen is based on the knowledge 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
VDDANA
GND
Switch
Resistor
Switch
Resistor
XPos Measure(Yp)
Y
P
Y
M
Open
circuit
Rp
X
P
X
M
VDDANA
GND
Switch
Resistor
Switch
Resistor
Z1 Measure(Xp)
Y
P
Y
M
Open
circuit
Rp
X
P
X
M
VDDANA
GND
Switch
Resistor
Switch
Resistor
Z2 Measure(Xp)
Y
P
Y
M
Open
circuit
Rp