test.pde

#define DIR_PIN 2
#define STEP_PIN 3

void setup() { 
  pinMode(DIR_PIN, OUTPUT); 
  pinMode(STEP_PIN, OUTPUT); 
} 

void loop(){ 
  rotate(1600, .25);
  delay(1000); 
}

void rotate(int steps, float speed){ 
  int dir = (steps > 0)? HIGH:LOW;
  steps = abs(steps);

  digitalWrite(DIR_PIN,dir); 

  float usDelay = (1/speed) * 70;

  for(int i=0; i < steps; i++){ 
    digitalWrite(STEP_PIN, HIGH); 
    delayMicroseconds(usDelay); 

    digitalWrite(STEP_PIN, LOW); 
    delayMicroseconds(usDelay); 
  } 
}