https://medium.com/jungletronics/uln2003-28byj-48-stepper-motor-f1cc5357eff

_61_ULN2003_FULL_STEP_DRIVE_02.ino

// Full Step

#define stepper PORTB
#define waiting_time 500

void setup() {
  for (int z = 8; z < 12; z++) {  // FULL STEP DRIVE
    pinMode(z, OUTPUT);           // pins 8,9,10,11 output for driving the motor

  }
}

void loop() {

  stepper = 0B0011;               // 0x03;

  delay(waiting_time);

  stepper = 0B0110;               // 0x06;

  delay(waiting_time);

  stepper = 0B1100;               // 0x0C;

  delay(waiting_time);
  stepper = 0B1001;               // 0x09;

  delay(waiting_time);

}