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

const byte filas = 4;
const byte columnas = 4;

byte pinFilas[filas] = {2,3,4,5};
byte pinColumnas[columnas] = {6,7,8,9};

char teclas[filas][columnas] = {
  {'1','2','3','A'},
  {'4','5','6','B'},
  {'7','8','9','C'},
  {'*','0','.','D'}
};

Keypad teclado = Keypad(makeKeymap(teclas), pinFilas, pinColumnas, filas, columnas);

LiquidCrystal_I2C lcd(0x27, 16, 2);

int i, count = 0;
String v, a;
float volt, amper, watts;

void setup() {
  // put your setup code here, to run once:
  Serial.begin(9600);
  lcd.init();
  lcd.backlight();
  lcd.setCursor(0,0);
  lcd.print("Ingrese voltaje");
}

void loop() {
  volt = voltaje();
  amper = amperes();
  watts = volt * amper;
  lcd.setCursor(0,0);
  lcd.print("Watts obtenidos");
  lcd.setCursor(0,1);
  lcd.print(watts);
  lcd.print(" [W]");
}

float voltaje(){
  float voltios = 0.0;
  while(count < 8){
    char c = teclado.getKey(); //verifico si hay tecla
    if(c >= '0' && c <= '9' || c == '.'){
      v += c;
      lcd.setCursor(0,0);
      lcd.print("Ingrese voltaje");
      lcd.setCursor(0,1);
      lcd.print(v);
      count++;
    }
    if(c == 'C'){
      v = "";
      lcd.clear();
      delay(1000);
      lcd.print("Ingrese voltaje");
      lcd.setCursor(0,1);
      count = 0;
    }
    if(c == 'A'){
      voltios = v.toFloat();
      v = "";
      lcd.clear();
      break;
    }
  }
  return voltios;
}

float amperes(){
  float amperios = 0.0;
  lcd.setCursor(0,0);
  lcd.print("Ingrese amperaje");
  count = 0;
  while(count < 8){
    char c = teclado.getKey(); //verifico si hay tecla
    if(c >= '0' && c <= '9' || c == '.'){
      a += c;
      lcd.setCursor(0,0);
      lcd.print("Ingrese amperaje");
      lcd.setCursor(0,1);
      lcd.print(a);
      count++;
    }
    if(c == 'C'){
      a = "";
      lcd.clear();
      delay(1000);
      lcd.print("Ingrese amperaje");
      lcd.setCursor(0,1);
      count = 0;
    }
    if(c == 'A'){
      amperios = a.toFloat();
      a = "";
      lcd.clear();
      break;
    }
  }
  return amperios;
}