#define m1 27
#define m2 14
#define m3 12
#define m4 13

int ec = 22;
int tr = 23;

void setup() {
  pinMode(m1, OUTPUT);
  pinMode(m2, OUTPUT);
  pinMode(m3, OUTPUT);
  pinMode(m4, OUTPUT);
  digitalWrite(m1, 0);
  digitalWrite(m2, 0);
  digitalWrite(m3, 0);
  digitalWrite(m4, 0);

  pinMode(ec, INPUT);
  pinMode(tr, OUTPUT);
  digitalWrite(tr, LOW);
}

void loop() {
  if(distancia() >= 20){
  adelante();
  }
  else{
  alto();
  delay(1000);
  atras();
  delay(500);
  izquierda();
  delay(500);
}
}

long distancia()
{
long t;
long d;
digitalWrite(tr, HIGH);
delayMicroseconds(10);
digitalWrite(tr, LOW);
t = pulseIn(ec, HIGH, 15000);
d = (t == 0) ? 400 : t / 59;
delay(10);
return d;
}

void alto(){
  digitalWrite(m1, 0);
  digitalWrite(m2, 0);
  digitalWrite(m3, 0);
  digitalWrite(m4, 0);
}

void atras(){
  digitalWrite(m1, 0);
  digitalWrite(m2, 1);
  digitalWrite(m3, 1);
  digitalWrite(m4, 0);
}

void adelante(){
  digitalWrite(m1, 1);
  digitalWrite(m2, 0);
  digitalWrite(m3, 0);
  digitalWrite(m4, 1);
}

void derecha(){
  digitalWrite(m1, 1);
  digitalWrite(m2, 0);
  digitalWrite(m3, 1);
  digitalWrite(m4, 0);
}

void izquierda(){
  digitalWrite(m1, 0);
  digitalWrite(m2, 1);
  digitalWrite(m3, 0);
  digitalWrite(m4, 1);
}

void izq1(){
  digitalWrite(m1, 0);
  digitalWrite(m2, 0); 
  digitalWrite(m3, 0); 
  digitalWrite(m4, 1);
}

void der1(){
  digitalWrite(m1, 1);
  digitalWrite(m2, 0); 
  digitalWrite(m3, 0); 
  digitalWrite(m4, 0);
}

void atrasizquierda(){
  digitalWrite(m1, 0);
  digitalWrite(m2, 0); 
  digitalWrite(m3, 1); 
  digitalWrite(m4, 0);
}

void atrasderecha(){
  digitalWrite(m1, 0);
  digitalWrite(m2, 1); 
  digitalWrite(m3, 0); 
  digitalWrite(m4, 0);
}