Two steppers on a CNC shield, on an Arduino Uno

// Two stepper motors on the CNC shield v3, X and Y.
//
//   X: STEP 2, DIR 5     Y: STEP 3, DIR 6     enable (all drivers): 8, LOW = on
//
// The shield pulls pin 8 high, so the drivers stay off until the sketch
// drives it low. Its jumpers set 1/16 microstepping: 3200 steps a turn.

const uint8_t X_STEP = 2, Y_STEP = 3, X_DIR = 5, Y_DIR = 6, ENABLE = 8;
const int STEPS_PER_TURN = 3200;

void steps(int count, unsigned int us) {
  for (int i = 0; i < count; i++) {
    digitalWrite(X_STEP, HIGH);
    digitalWrite(Y_STEP, HIGH);
    delayMicroseconds(5);
    digitalWrite(X_STEP, LOW);
    digitalWrite(Y_STEP, LOW);
    delayMicroseconds(us);
  }
}

void setup() {
  pinMode(X_STEP, OUTPUT);
  pinMode(Y_STEP, OUTPUT);
  pinMode(X_DIR, OUTPUT);
  pinMode(Y_DIR, OUTPUT);
  pinMode(ENABLE, OUTPUT);
  digitalWrite(ENABLE, LOW);
}

void loop() {
  // A quarter turn one way, X and Y opposite...
  digitalWrite(X_DIR, HIGH);
  digitalWrite(Y_DIR, LOW);
  steps(STEPS_PER_TURN / 4, 300);
  delay(300);
  // ...and back.
  digitalWrite(X_DIR, LOW);
  digitalWrite(Y_DIR, HIGH);
  steps(STEPS_PER_TURN / 4, 300);
  delay(300);
}