void setup()
{
 Serial.begin(115200);
 }
 void loop() 
{
 pinMode(13,OUTPUT);
 digitalWrite(13,0);
 delayMicroseconds(2);
 digitalWrite(13,1);
 delayMicroseconds(5);
 digitalWrite(13,0);
  pinMode(12,INPUT);
 long t = pulseIn(12,1);
 Serial.println(t);
 delay(200);
}