To perform the sensing the following steps are important:
DOT   Drive a secondary channel to Vdd an das digital output
DOT   Point the ADC tot he secondary pin with the Vdd-Level (charges the internal capacitor to Vdd)
DOT   Ground the sensor line
DOT   Set the sensor line as input
DOT   Point the ADC to sensor channel (the internal capacitor discharges)
DOT   Begin the ADC conversion

And at least evaluate the digital value and compare it with the „pressed value“