/*
 * Bas on Tech - Rotary Encoder and Interrupts
 * This course is part of the courses on https://arduino-tutorials.net
 *  
 * (c) Copyright 2018-2019 - Bas van Dijk / Bas on Tech
 * This code and course is copyrighted. It is not allowed to use these courses commerically
 * without explicit written approval
 * 
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 * 
 * ---------------------------------------------------------------------------
 * 
 * More info about the Rotary Encoder: 
 * https://en.wikipedia.org/wiki/Rotary_encoder
 * 
 * PIN CONNECTIONS
 *
 * GND --> GND black
 *  +  --> 5V  red
 * SW  --> 12  yellow
 * DT  --> 2   green (data)
 * CLK --> 3   blue (clock)
 *
 */

int switchPin = 12;                        // button pin
int switchState = HIGH;                    // button value

int pinA = 2;                              // Rotary encoder Pin A / DT
int pinB = 3;                              // Rotary encoder Pin B / CLK
int pinAstateCurrent = LOW;                // Current state of Pin A
int pinAStateLast = pinAstateCurrent;      // Last read value of Pin A

void setup() {
  Serial.begin (9600);                     // Initialise the serial monitor

  pinMode (switchPin, INPUT_PULLUP);       // Enable the switchPin as input with a PULLUP resistor
    
  pinMode (pinA, INPUT);                   // Set PinA as input
  pinMode (pinB, INPUT);                   // Set PinB as input

  // Atach a CHANGE interrupt to PinB and exectute the update function when this change occurs.
  attachInterrupt(digitalPinToInterrupt(pinB), update, CHANGE);
  
}

void loop() {

  // BUTTON
  switchState = digitalRead(switchPin);    // Read the digital value of the switch (LOW/HIGH)

  // If the switch is pressed (LOW), print message
  if (switchState == LOW) {
      Serial.println("Switch pressed");
  }
    
}

void update() {

  /* WARNING: For this example I've used Serial.println within the interrupt callback. The Serial 
   * library already uses interrupts which could cause errors. Therefore do not use functions 
   * of the Serial libray in your interrupt callback.
   */

  // ROTATION DIRECTION
  pinAstateCurrent = digitalRead(pinA);    // Read the current state of Pin A
  
  // If there is a minimal movement of 1 step
  if ((pinAStateLast == LOW) && (pinAstateCurrent == HIGH)) {
    
    if (digitalRead(pinB) == HIGH) {      // If Pin B is HIGH
      Serial.println("Right");             // Print on screen
    } else {
      Serial.println("Left");            // Print on screen
    }
    
  }
  
  pinAStateLast = pinAstateCurrent;        // Store the latest read value in the currect state variable
  
}