// ULN2003 stepper driver - one step or forward and reverse.

#include <Stepper.h>

#define IN1 10 // input pins for ULN2003 driver with BYJ28-48 stepper
#define IN2  8
#define IN3  6
#define IN4  4

#define ledFWD  2 // forward LED
#define ledREV 12 // reverse LED

byte pinOut[] = {2, 4, 6, 8, 10, 12}; // output pins

int stepDir = 1; // motor direction 1 (FWD) or -1 (REV)
int stepCount = 0; // counter
int stepsPerRevolution = 2048; // motor specific

Stepper myStepper(stepsPerRevolution, IN1, IN3, IN2, IN4); // Create stepper object, windings 1, 3, 2, 4

unsigned long timer, interval = 250;// timer for onestep()

void setup() {
  Serial.begin(115200);
  for (int i = 0; i < 6; i++)
    pinMode (i, OUTPUT);
  digitalWrite(ledFWD, HIGH);
  digitalWrite(ledREV, LOW);
}

void loop() {
  if (millis() - timer > interval) { // wait for interval
    timer = millis(); // reset timer
    // onestep(); // advance motor one step
    freerun();
  }
}

void onestep() {
    myStepper.step(1); // advance motor one step
}

void freerun() {
  if (millis() < interval + 50) Serial.print("FWD | "); // print once

  Serial.print(stepCount % 4); // four steps of ULN2003
  myStepper.step(1 * stepDir); // "steps" and "direction"
  stepCount++;
  if (!(stepCount % 20)) { // at 20 steps
    Serial.println(); // format serial output
    stepCount = 0; // reset step count
    stepDir = -stepDir; // change motor direction
    if (stepDir > 0) {
      Serial.print("FWD | ");
      digitalWrite(ledFWD, HIGH); // indicate direction
      digitalWrite(ledREV, LOW); // indicate direction
    } else {
      Serial.print("REV | ");
      digitalWrite(ledFWD, LOW); // indicate direction
      digitalWrite(ledREV, HIGH); // indicate direction
    }
  }
}