#include <Arduino.h>
#include <Wire.h>
#include <LiquidCrystal_I2C.h> 
#include <Keypad.h>
#include <HX711.h>

#define NUM_KEYS 4
char button_pressed[NUM_KEYS];
int k = 1;

#define buzzer 2

#define DT 3
#define SCK 4
HX711 scale;
float scale_calibration = 0;
float weight_units;
float weight_gr;
float delta;

LiquidCrystal_I2C lcd(0x27, 20, 4);

const byte ROWS = 4;
const byte COLS = 4;
char keys[ROWS][COLS] =
{
  {'1','2','3','A'},
  {'4','5','6','B'},
  {'7','8','9','C'},
  {'*','0','#','D'}
};
byte rowPins[ROWS] = {14, 15, 16, 17};
byte colPins[COLS] = {18, 19, 20, 21};
Keypad keypad = Keypad(makeKeymap(keys), rowPins, colPins, ROWS, COLS);

void setup()
{
  Serial.begin(9600);
  lcd.init();
  lcd.backlight();
  lcd.setCursor(0, 0);
  lcd.print("Enter weight:");
  lcd.setCursor(0, 2);
  lcd.print("Weight:");
  
  scale.begin(DT, SCK);
  scale.set_scale();
  scale.tare();
}
  
void loop()
{
  char key = keypad.getKey();
  if (key != NO_KEY)
  {
    button_pressed [k] = key;
    Serial.print(key);
    lcd.setCursor(0, 1);
    lcd.print(key);

    scale.set_scale(scale_calibration);
  }
  
  Serial.print("Read data: ");
  weight_units = scale.get_units(), 10;
  if (weight_units < 0){
    weight_units = 0.00;
  }
  weight_gr = weight_units * 0.035274;
  Serial.print(weight_gr);
  Serial.println(" grams");
  lcd.setCursor(0, 3);
  lcd.print(weight_gr);

  delta = key - weight_gr;
    if(delta + 1 > 0)
  {
    tone(2, 1000, 3000);
  }
  else if(delta - 1 < 0)
  {
    tone(2, 500, 3000);
  }
  else
  {
    noTone(2);
  }
}