int trigger=4; 
int echo=5; 
long dauer=0; 
long entfernung=0; 


int LeftMotorForward = 6; 
int LeftMotorReverse = 7; 
int RightMotorForward = 8;
int RightMotorReverse = 9;




void setup()
{
Serial.begin (9600); 
pinMode(trigger, OUTPUT); 
pinMode(echo, INPUT); 
  
  pinMode(LeftMotorForward, OUTPUT); 
  pinMode(LeftMotorReverse, OUTPUT);     
  pinMode(RightMotorForward, OUTPUT); 
  pinMode(RightMotorReverse, OUTPUT); 
}



void loop()
{
digitalWrite(trigger, LOW); 
delay(5); 
digitalWrite(trigger, HIGH); 
delay(10);
digitalWrite(trigger, LOW);
dauer = pulseIn(echo, HIGH); 
entfernung = (dauer/2) * 0.03432; 
/////////////////////////////////////

if (entfernung <= 15){
Serial.print(entfernung); 
Serial.println(" - Abstand kleiner als 15 cm"); 
stoppen();
zurueck();
delay(700);
stoppen();
rechts();
stoppen();
}

else {
Serial.print(entfernung); 
Serial.println(" cm"); 
vor();
}

delay(100); 
}//Ende Loop


//////// Subroutinen /////////////////////////////

 void stoppen(){
   digitalWrite(RightMotorForward, LOW); 
   digitalWrite(LeftMotorForward,  LOW);  
   digitalWrite(RightMotorReverse, LOW); 
   digitalWrite(LeftMotorReverse,  LOW);  
}

 void links(){
   digitalWrite(RightMotorForward, HIGH); 
   digitalWrite(LeftMotorForward,  LOW);  
   digitalWrite(RightMotorReverse, LOW); 
   digitalWrite(LeftMotorReverse,  HIGH);  
   
   delay(300);
   digitalWrite(RightMotorForward, LOW); 
   digitalWrite(LeftMotorForward,  LOW);  
   digitalWrite(RightMotorReverse, LOW); 
   digitalWrite(LeftMotorReverse,  LOW);
   
}
    
void rechts(){
   digitalWrite(RightMotorForward, LOW); 
   digitalWrite(LeftMotorForward,  HIGH);  
   digitalWrite(RightMotorReverse, HIGH); 
   digitalWrite(LeftMotorReverse,  LOW);  
   
   delay(300);
   digitalWrite(RightMotorForward, LOW); 
   digitalWrite(LeftMotorForward,  LOW);  
   digitalWrite(RightMotorReverse, LOW); 
   digitalWrite(LeftMotorReverse,  LOW);
}
    
void vor(){
   digitalWrite(RightMotorForward, HIGH); 
   digitalWrite(LeftMotorForward,  HIGH);  
   digitalWrite(RightMotorReverse, LOW); 
   digitalWrite(LeftMotorReverse,  LOW);  

}

void zurueck(){
   digitalWrite(RightMotorForward, LOW); 
   digitalWrite(LeftMotorForward,  LOW);  
   digitalWrite(RightMotorReverse, HIGH); 
   digitalWrite(LeftMotorReverse,  HIGH);  
}