/* KY-040 Rotary Encoder Counter

   Rotate clockwise to count up, counterclockwise to counter done.

   Press to reset the counter.

   Copyright (C) 2021, Uri Shaked
*/

#include <LiquidCrystal_I2C.h>
LiquidCrystal_I2C lcd(0x27, 20, 4);

uint8_t ENCODER_CLK[2] = {2,5};
uint8_t ENCODER_DT[2] = {3,6};
uint8_t ENCODER_SW[2] = {4,7};

int counter[2] = {0,0};

void setup() {
  // Initialize LCD
  lcd.init();
  lcd.backlight();

  // Initialize encoder pins
  pinMode(ENCODER_CLK[0], INPUT);
  pinMode(ENCODER_DT[0], INPUT);
  pinMode(ENCODER_SW[0], INPUT_PULLUP);
  attachInterrupt(digitalPinToInterrupt(ENCODER0_CLK[0]), readEncoder, FALLING);
}

void readEncoder(uint8_t idx) {
  int dtValue = digitalRead(ENCODER_DT[idx]);
  if (dtValue == HIGH) {
    counter[idx]++; // Clockwise
  }
  if (dtValue == LOW) {
    counter[idx]--; // Counterclockwise
  }
}

// Get the counter value, disabling interrupts.
// This make sure readEncoder() doesn't change the value
// while we're reading it.
int getCounter(uint8_t idx) {
  int result;
  noInterrupts();
  result = counter[idx];
  interrupts();
  return result;
}

void resetCounter(uint8_t idx) {
  noInterrupts();
  counter[idx] = 0;
  interrupts();
}

void loop() {
  lcd.setCursor(3, 0);
  lcd.print("Counter:");
  lcd.setCursor(7, 1);
  lcd.print(getCounter(0));
  lcd.print("        ");

  if (digitalRead(ENCODER_SW[0]) == LOW) {
    resetCounter(0);
  }
}