potentiometer_start_at_0.ino

int potPin = A5;    // select the input pin for the potentiometer
int ledPin = 13;   // select the pin for the LED
int val = 0;       // variable to store the value coming from the sensor

// from https://bildr.org/2012/08/rotary-encoder-arduino/

int orange = 4;
int green = 2;

volatile int lastEncoded = 0;
volatile long encoderValue = 0;

long lastencoderValue = 0;
int lastMSB = 0;
int lastLSB = 0;

void setup() {
  Serial.begin(9600);
  pinMode(ledPin, OUTPUT);  // declare the ledPin as an OUTPUT

  pinMode(orange, INPUT);
  pinMode(green, INPUT);

  digitalWrite(orange, HIGH); //turn pullup resistor on
  digitalWrite(green, HIGH); //turn pullup resistor on

  //call updateEncoder() when any high/low changed seen
  //on interrupt 0 (pin 2), or interrupt 1 (pin 3)
  attachInterrupt(0, updateEncoder, CHANGE);
  attachInterrupt(1, updateEncoder, CHANGE);
}



void loop() {
  //val = analogRead(potPin);    // read the value from the sensor
  Serial.println(encoderValue);
  digitalWrite(ledPin, HIGH);  // turn the ledPin on
  delay(500);                  // stop the program for some time
  digitalWrite(ledPin, LOW);   // turn the ledPin off
  delay(500);                  // stop the program for some time
}



void updateEncoder(){
  int MSB = digitalRead(orange); //MSB = most significant bit
  int LSB = digitalRead(green); //LSB = least significant bit
  
  int encoded = (MSB << 1) |LSB; //converting the 2 pin value to single number 
  int sum = (lastEncoded << 2) | encoded; //adding it to the previous encoded value 
  if(sum == 0b1101 || sum == 0b0100 || sum == 0b0010 || sum == 0b1011) 
    encoderValue ++;
  if(sum == 0b1110 || sum == 0b0111 || sum == 0b0001 || sum == 0b1000) 
    encoderValue --; 
   lastEncoded = encoded; //store this value for next time

   //
   Serial.println(encoderValue);
}