#include <Stepper.h>
const int nominalStepsPerRevolution = 2048;
const byte in1 = 8, in2 = 9, in3 = 10, in4 = 11;
Stepper motor(nominalStepsPerRevolution, in1, in3, in2, in4);

void releaseCoils() {
  digitalWrite(in1, LOW); digitalWrite(in2, LOW);
  digitalWrite(in3, LOW); digitalWrite(in4, LOW);
}

void setup() {
  Serial.begin(9600);
  motor.setSpeed(5);
  releaseCoils();
  Serial.println("Send f or r for 256 steps");
}

void loop() {
  if (Serial.available() > 0) {
    const char command = Serial.read();
    if (command == 'f' || command == 'r') {
      motor.step(command == 'f' ? 256 : -256);
      releaseCoils();
      Serial.println("Move finished; coils released");
    }
  }
}