step.c

#include <CustomStepper.h>
CustomStepper stepper(2, 3, 4, 5);

int key_pin = 12;

int KEY_PRESSED = 0;
int is_rotate = false;

void setup()
{
  pinMode(key_pin, INPUT);
  stepper.setRPM(12);
  stepper.setSPR(4075.7728395);
  Serial.begin(9600);
  Serial.println("Start");
}

void loop()
{
  // значение кнопки
  KEY_PRESSED = digitalRead(key_pin);

  if (stepper.isDone() && KEY_PRESSED == 1){
      Serial.println("Rotate");
      stepper.setDirection(CCW);
      stepper.rotate();
      is_rotate = true;
  }
  if (KEY_PRESSED == 0 && is_rotate == true){
      Serial.println("Stop");
      stepper.setDirection(STOP); 
      is_rotate = false;
  }
  
  stepper.run();
}