#include <Stepper.h>
#define potpin A0

int val, last;

Stepper myStepper(val, 8, 9, 10, 11);

void setup() {
  myStepper.setSpeed(60);
  Serial.begin(9600);
  pinMode(potpin, INPUT);
}

void loop() {
  val = analogRead(potpin);
  val = map(val, 0, 1023, 0, 200);
  myStepper.step(val-last);
  last = val;
  delay(15);
}