Rotary Encoder + Button Keyboard Output (Arduino Pro Micro)

rotarykey.ino

#include <Keyboard.h>
/* interrupt routine for Rotary Encoders
   tested with Noble RE0124PVB 17.7FINB-24 https://www.nobleusa.com/pdf/xre.pdf - available at pollin.de
   and a few others, seems pretty universal

   The average rotary encoder has three pins, seen from front: A C B
   Clockwise rotation A(on)->B(on)->A(off)->B(off)
   CounterCW rotation B(on)->A(on)->B(off)->A(off)

   and may be a push switch with another two pins, pulled low at pin 8 in this case
   raf@synapps.de 20120107
   modified to keyboard Version davidgrieshammer.com 20191101
*/

// usually the rotary encoders three pins have the ground pin in the middle
enum PinAssignments {
  encoderPinA = 2,   // right
  encoderPinB = 3,   // left
  clearButton = 7    // another two pins
};

volatile unsigned int encoderPos = 0;  // a counter for the dial
unsigned int lastReportedPos = 1;   // change management
static boolean rotating = false;    // debounce management

volatile int rotationPos = 0; // can be 0, -1, 1

// interrupt service routine vars
boolean A_set = false;
boolean B_set = false;
boolean clicked = false;

void setup() {
  pinMode(encoderPinA, INPUT);
  pinMode(encoderPinB, INPUT);
  pinMode(clearButton, INPUT);
  // turn on pullup resistors
  digitalWrite(encoderPinA, HIGH);
  digitalWrite(encoderPinB, HIGH);
  digitalWrite(clearButton, LOW);

  // encoder pin on interrupt 0 (pin 2)
  attachInterrupt(0, doEncoderA, CHANGE);
  // encoder pin on interrupt 1 (pin 3)
  attachInterrupt(1, doEncoderB, CHANGE);
  Keyboard.begin();
  //Serial.begin(9600);  // output
}

// main loop, work is done by interrupt service routines, this one only prints stuff
void loop() {
  rotating = true;  // reset the debouncer

  if(rotationPos == -1) {
    Keyboard.press(KEY_LEFT_ARROW);
    Keyboard.releaseAll();
    //Serial.println("Left");
    rotationPos = 0;
  }
  if(rotationPos == 1) {
    Keyboard.press(KEY_RIGHT_ARROW);
    Keyboard.releaseAll();
    //Serial.println("Right");
    rotationPos = 0;
  }
  
  if (digitalRead(clearButton) == HIGH && clicked == false)  {
    clicked = true;
    rotationPos = 0;
    //Serial.println("click");
    Keyboard.press(KEY_DOWN_ARROW);
    Keyboard.releaseAll();
    delay(50);
  }
  if(clicked == true && digitalRead(clearButton) == LOW) {
    clicked = false;
    delay(50);
  }
}

// Interrupt on A changing state
void doEncoderA() {
  // debounce
  if ( rotating ) delay (1);  // wait a little until the bouncing is done

  // Test transition, did things really change?
  if ( digitalRead(encoderPinA) != A_set ) { // debounce once more
    A_set = !A_set;

    // adjust counter + if A leads B
    if ( A_set && !B_set )
      // encoderPos += 1;
      rotationPos = 1;

    rotating = false;  // no more debouncing until loop() hits again
  }
}

// Interrupt on B changing state, same as A above
void doEncoderB() {
  if ( rotating ) delay (1);
  if ( digitalRead(encoderPinB) != B_set ) {
    B_set = !B_set;
    //  adjust counter - 1 if B leads A
    if ( B_set && !A_set )
      //encoderPos -= 1;
      rotationPos = -1;

    rotating = false;
  }
}