// For: https://forum.arduino.cc/t/interrupt-freezes-arduino-and-stops-code-from-working/1081767
//
// Changes:
//   - Using the KISS rule.
//   - Changed to hd4470 library.
//   - It is not possible to use I2C (interrupt driven).
//     or delay() in a interrupt. Serial.print() should be avoided.
//   - Interrupt at falling edge to toggle the background.
//
// Conclusion: 
//   This does not feel right.
//   The button can be checked in the loop().
//   A interrupt makes debouncing harder.
//   The Encoder library can deal with the encoder:
//     https://www.pjrc.com/teensy/td_libs_Encoder.html
//


#include <Wire.h>
#include <hd44780.h>
#include <hd44780ioClass/hd44780_I2Cexp.h>

hd44780_I2Cexp lcd;

// LCD geometry
const int LCD_COLS = 16;
const int LCD_ROWS = 2;

const int encoderCLK = 19;
const int encoderDT  = 45;
const int encoderBtn = 18;

bool backlight = true;       // the current status of the backlight
volatile bool trigger = false; // to send a trigger from interrupt routine

void setup()
{
  Serial.begin(115200);
  pinMode(encoderBtn, INPUT_PULLUP);
  attachInterrupt(digitalPinToInterrupt(encoderBtn), lcd_power_toggle, FALLING);

  Wire.begin();             // not really needed, lcd.begin will do this

  int status = lcd.begin(LCD_COLS, LCD_ROWS); // also turn on backlight
  if(status) // non zero status means it was unsuccesful
  {
    Serial.println("Display was not found");
  }

  lcd.setCursor(0, 0);      // column, row
  lcd.print( "To Freeze Or");
  lcd.setCursor(0, 1);      // column, row
  lcd.print( "Not To Freeze");
}

void loop()
{
  if(trigger)
  {
    trigger = false;       // reset the trigger
    backlight = !backlight; // toggle between true and false
    if( backlight)
    {
      lcd.backlight();    // turn backlight on.
    }
    else
    {
      lcd.noBacklight();  // turn backlight off.
    }
  }
  delay(20);              // slow down the sketch, avoid button bounce trouble.
}

void lcd_power_toggle()
{
  trigger = true;
}