blabla

// constants won't change. They're used here to set pin numbers:
const int buttonPin = 7;     // the number of the pushbutton pin
const int ledPin =  3;      // the number of the LED pin

// variables will change:
int buttonState = 0;         // variable for reading the pushbutton status
int anterior = 0;
int ledState = 0;

void setup() {
  // initialize the LED pin as an output:
  pinMode(ledPin, OUTPUT);
  // initialize the pushbutton pin as an input:
  pinMode(buttonPin, INPUT);
}

void loop() {
  // read the state of the pushbutton value:
  buttonState = digitalRead(buttonPin);

  // check if the pushbutton is pressed. If it is, the buttonState is HIGH:
  if ((buttonState == HIGH) && (anterior == LOW)) {
    // HAY PULSACION

    if (ledState == HIGH) {
      // turn LED off:
      digitalWrite(ledPin, LOW);
      ledState = LOW;
    }
    else {
      // turn LED on:
      digitalWrite(ledPin, HIGH);
      ledState = HIGH;
      }
  }
  anterior = buttonState;

  delay(100);
}