int Pin0 = 10; 
int Pin1 = 11; 
int Pin2 = 12; 
int Pin3 = 13; 
int _step = 0; 
boolean dir = true;// gre
void setup() 
{ 
 pinMode(Pin0, OUTPUT);  
 pinMode(Pin1, OUTPUT);  
 pinMode(Pin2, OUTPUT);  
 pinMode(Pin3, OUTPUT);  
} 
 void loop() 
{ 
 switch(_step){ 
   case 0: 
     digitalWrite(Pin0, LOW);  
     digitalWrite(Pin1, LOW); 
     digitalWrite(Pin2, LOW); 
     digitalWrite(Pin3, HIGH); 
   break;  
   case 1: 
     digitalWrite(Pin0, LOW);  
     digitalWrite(Pin1, LOW); 
     digitalWrite(Pin2, HIGH); 
     digitalWrite(Pin3, HIGH); 
   break;  
   case 2: 
     digitalWrite(Pin0, LOW);  
     digitalWrite(Pin1, LOW); 
     digitalWrite(Pin2, HIGH); 
     digitalWrite(Pin3, LOW); 
   break;  
   case 3: 
     digitalWrite(Pin0, LOW);  
     digitalWrite(Pin1, HIGH); 
     digitalWrite(Pin2, HIGH); 
     digitalWrite(Pin3, LOW); 
   break;  
   case 4: 
     digitalWrite(Pin0, LOW);  
     digitalWrite(Pin1, HIGH); 
     digitalWrite(Pin2, LOW); 
     digitalWrite(Pin3, LOW); 
   break;  
   case 5: 
     digitalWrite(Pin0, HIGH);  
     digitalWrite(Pin1, HIGH); 
     digitalWrite(Pin2, LOW); 
     digitalWrite(Pin3, LOW); 
   break;  
     case 6: 
     digitalWrite(Pin0, HIGH);  
     digitalWrite(Pin1, LOW); 
     digitalWrite(Pin2, LOW); 
     digitalWrite(Pin3, LOW); 
   break;  
   case 7: 
     digitalWrite(Pin0, HIGH);  
     digitalWrite(Pin1, LOW); 
     digitalWrite(Pin2, LOW); 
     digitalWrite(Pin3, HIGH); 
   break;  
   default: 
     digitalWrite(Pin0, LOW);  
     digitalWrite(Pin1, LOW); 
     digitalWrite(Pin2, LOW); 
     digitalWrite(Pin3, LOW); 
   break;  
 } 
 if(dir){ 
   _step++; 
 }else{ 
   _step--; 
 } 
 if(_step>7){ 
   _step=0; 
 } 
 if(_step<0){ 
   _step=7; 
 } 
 delay(1); 
}