Arduino pull-up resistor not working - arduino

Question

I am using an Arduino board to read out the value of a soft potmeter. (a strip that detects touch). This works perfectly fine as long as the strip is being touched (a resistance is added to the current).
When the strip is not touched, a completely random floating number is read by the analog pin. Forums mention that you have to add a pullup/pulldown resistor to cancel this effect, but this does not seem te be working. What is wrong with this code?
int potPin = 2;
int curval = 0;
// detect potmeter value
void setup() {
//enable pullup resistor, but still results in erratic output
//when potmeter is not touched
digitalWrite(potPin, HIGH);
//write to serial
Serial.begin(9600);
}
void loop() {
curval = analogRead(potPin);
// this works when the potmeter is being pressed (displays 0 to 1024)
Serial.println(curval);
delay(150);
}

Answer 1

Change
int potPin = 2;
to
int potPin = A2;
Your original use of "2" in both places is assigning Digital Pin 2 to pull-up and reading from Analog Channel 2. As "2" maps correspondingly to is PortD bit 2 and Analog Channel 2 (aka ADC2) is PortC bit 2. As shown below
digitalWrite(2, HIGH); // Pin D2
curval = analogRead(2); // AMUX Channel 2
where A2 shown below is interpreted as follows
digitalWrite(A2, HIGH); // Pin (A2 aka D16)
curval = analogRead(A2); // AMUX Channel 2 on Pin A2
On an UNO (ATmega328) the analogRead() function will interpret 0-7 as channels and will convert the pins A0 through A7 (D14-D21) to corresponding channels, to read from.
Note:
ADC6 and 7 are not available on the chip used on the UNO.
A0-A7 are alias for Digital 14 through 21. Where the labels A0-A7 are typically used.