#include <Stepper.h>
int stepsPerRevolution=200;
Stepper myStepper(stepsPerRevolution,8,9,10,11);
int motSpeed=10;
int dt=500;
int buttonPin=2;
int motDir=1;
int buttonvalnew;
int buttonvalold=1;

void setup() {
  // put your setup code here, to run once:
  Serial.begin(9600);
  myStepper.setSpeed(motSpeed);
  pinMode(buttonPin, INPUT);
  digitalWrite(buttonPin, HIGH);

}

void loop() {
  // put your main code here, to run repeatedly:
  buttonvalnew=digitalRead(buttonPin);
  if(buttonvalnew==0 && buttonvalold==1){
    motDir*=-1;
  }
  myStepper.step(motDir);
  buttonvalold=buttonvalnew;
}