const int DIR_1 = 5;
const int STEP_1 = 6;
const int STEP_REV = 200;
int PULSE=1000;

void setup() {
pinMode(STEP_1, OUTPUT);
pinMode(DIR_1, OUTPUT);
digitalWrite(DIR_1, HIGH);
Serial.begin(9600); // opens serial port, sets data rate to 9600 bps

}

void loop() {

if (Serial.available() > 0) {

PULSE = Serial.read(); // read the incoming byte:
stepper1_on();


}

}

void stepper1_on(void)                    
{
  digitalWrite(STEP_1, HIGH);
  delayMicroseconds(PULSE);
  digitalWrite(STEP_1, LOW);
  delayMicroseconds(PULSE);
}