Teclado 3x4

void setup()
{
  pinMode(4, OUTPUT);
  pinMode(5, OUTPUT);
  pinMode(6, OUTPUT);
  pinMode(7, OUTPUT);

  pinMode(8, INPUT);
  digitalWrite(8, HIGH);
  pinMode(9, INPUT);
  digitalWrite(9, HIGH);
  pinMode(10, INPUT);
  digitalWrite(10, HIGH);

  Serial.begin(9600);
  Serial.println("Teclado 4x3");
  Serial.println("Aguardando acionamento");
  Serial.println();
}

void loop()
{
  for(int porta = 4; porta<8; porta ++)
  {
    digitalWrite(4, HIGH);
    digitalWrite(5, HIGH);
    digitalWrite(6, HIGH);
    digitalWrite(7, HIGH);
       digitalWrite(porta, LOW);


    if (digitalRead(8) == LOW)
    {
      imprime_linha_coluna(porta-3, 1);
      while(digitalRead(8) == LOW){}
    }
    if (digitalRead(9) == LOW)
    {
      imprime_linha_coluna(porta-3, 2);
      while(digitalRead(9) == LOW) {};
    }
    if (digitalRead(10) == LOW)
    {
      imprime_linha_coluna(porta-3, 3);
      while(digitalRead(10) == LOW) {};
   }
  }
delay(10);
}
void imprime_linha_coluna(int x, int y)
{
  Serial.print("Linha : ");
  Serial.print(x);
  Serial.print("x Coluna : ");
  Serial.print(y);
  delay(10);
  Serial.println();
}