#include <SoftwareSerial.h>
SoftwareSerial mySerial(0, 2); // RX, TX
const int boton = 3;
const int led = 1;
int buttonState = 0;
int value = 0;

void setup() {
  mySerial.begin(9600);
  pinMode(led, OUTPUT);
  pinMode(boton, INPUT);
}

void loop() { 

  for (value = 0; value <= 400; value += 50) {
    mySerial.print('1');
    digitalWrite(led, HIGH);
    delay(value);

    mySerial.print('2');
    digitalWrite(led, LOW);
    delay(value);
  }
  for (value = 400; value >= 0; value -= 50) {
    mySerial.print('1');
    digitalWrite(led, HIGH);
    delay(value);

    mySerial.print('2');
    digitalWrite(led, LOW);
    delay(value);
  }
}