// Changing a setpoint with up and a down pushbutton switches.
// https://forum.arduino.cc/t/how-to-make-setpoint-with-push-button/893568/5


/*
   The circuit:
   - pushbutton attached to pin 2 from ground
   - the internal pullup on pin 2 is enabled
   - pushbutton attached to pin 3 from ground
   - the internal pullup on pin 3 is enabled  
*/

#include <LiquidCrystal_I2C.h>

LiquidCrystal_I2C lcd(0x27, 20, 4);

// these constants won't change:
const byte  upButtonPin = 2;
const byte  downButtonPin = 3;

// Variables will change:
int setpoint = 0;

bool setpointChanged = false;

void setup()
{
   // initialize the button pins as a input with internal pullup:
   pinMode(upButtonPin, INPUT_PULLUP);
   pinMode(downButtonPin, INPUT_PULLUP);
   
   // initialize serial communication:

  lcd.init();
  lcd.backlight();
  lcd.setCursor(0, 0);
  lcd.print("Setpoint Change"); 
  lcd.setCursor(0, 1);
  lcd.print("with 2 Buttons");
  delay(2000);
  lcd.clear();

}


void loop()
{
   checkUpButton();
   checkDownButton();
   if (setpointChanged == true)
   {
      lcd.setCursor(0, 0);
      lcd.print("New Setpoint=");
      lcd.setCursor(13, 0);
      lcd.print(setpoint);
      setpointChanged = false;
   }
}

void checkUpButton()
{
   boolean buttonState = 0;         // current state of the button
   static boolean lastButtonState = 0;     // previous state of the button
   static unsigned long timer = 0;
   unsigned long interval = 50;  // check 20 times a second
   if (millis() - timer >= interval)
   {
      timer = millis();

      // read the pushbutton input pin:
      buttonState = digitalRead(upButtonPin); 

      // compare the buttonState to its previous state
      if (buttonState != lastButtonState)
      {
         // if the state has changed, increment the counter
         if (buttonState == LOW)

         {
            // if the current state is LOW then the button went from off to on:
            setpoint++;
            setpointChanged = true;
         }
         // save the current state as the last state, for next time through the loop
         lastButtonState = buttonState;
      }
   }
}

void checkDownButton()
{
   boolean buttonState = 0;         // current state of the button
   static boolean lastButtonState = 0;     // previous state of the button
   static unsigned long timer = 0;
   unsigned long interval = 50;  // check 20 times a second
   if (millis() - timer >= interval)
   {
      timer = millis();

      // read the pushbutton input pin:
      buttonState = digitalRead(downButtonPin);

      // compare the buttonState to its previous state
      if (buttonState != lastButtonState)
      {
         // if the state has changed, increment the counter
         if (buttonState == LOW)
         {
            // if the current state is LOW then the button went from off to on:
            setpoint--;
            setpointChanged = true;
         }
         // save the current state as the last state, for next time through the loop
         lastButtonState = buttonState;
      }
   }
}