int echo_pin = 7;
int trig_pin = 8;
int green_led = 22;
int red_led = 21;
int dir = 26;
int step = 27;
float duration , distance;
void setup() {
  // put your setup code here, to run once:
  Serial1.begin(115200);
  pinMode(echo_pin , INPUT);
  pinMode(trig_pin , OUTPUT);
  pinMode(step , OUTPUT);
  pinMode(dir , OUTPUT);
  pinMode(green_led , OUTPUT);
  pinMode(red_led , OUTPUT);
}

void loop() {
  // put your main code here, to run repeatedly:
    digitalWrite(trig_pin , LOW);
    delayMicroseconds(2);
    digitalWrite(trig_pin , HIGH);
    delayMicroseconds(10);
    digitalWrite(trig_pin , LOW);

    duration = pulseIn(echo_pin , HIGH);
    distance = duration * 0.0343 / 2;

    if(distance <= 250){
      digitalWrite(dir,HIGH);
      for(int x = 0; x < 200; x++) {
        digitalWrite(step ,HIGH); 
        delayMicroseconds(5000); 
        digitalWrite(step ,LOW); 
        delayMicroseconds(5000); 
        if( x >= 100 ){
          digitalWrite(green_led , HIGH);
          digitalWrite(red_led , LOW);
        }else{
          digitalWrite(red_led, HIGH);
          digitalWrite(green_led, LOW);
        }
      }
        delay(1000);
        digitalWrite(dir , LOW);
    }
}