int IN1=5;
int IN2=6;
int IN3=7;
int IN4=8;
int ENA=9;
int ENB=10;
void setup()
{
for (int i = 5; i <11; i ++)
  {
    pinMode(i, OUTPUT);  
  }
}
void loop()
{
  // rotate CW
 digitalWrite(IN1,LOW);
 digitalWrite(IN2,HIGH);
analogWrite(ENA,200);
 digitalWrite(IN3,LOW);
 digitalWrite(IN4,HIGH);
analogWrite(ENB,200);
 delay(2000);
 // pause for 2S
 analogWrite(ENA,0);
analogWrite(ENB,0);
 delay(1000);
 // rotate CCW
 digitalWrite(IN1,HIGH);
 digitalWrite(IN2,LOW);
 analogWrite(ENA,100);
 digitalWrite(IN3,HIGH);
 digitalWrite(IN4,LOW);
analogWrite(ENB,100);
 delay(2000);
 // pause for 2S
 analogWrite(ENA,0);
analogWrite(ENB,0);
 delay(2000);
}