Read Buttons

#define NUM_LEDS 4

int position;

int interval;

int ledState;

unsigned long ptime;

void setup()

{

  Serial.begin(9600);

  pinMode(2, OUTPUT);

  pinMode(3, OUTPUT);

  pinMode(4, OUTPUT);

  pinMode(5, OUTPUT);

  pinMode(11, INPUT_PULLUP);

  pinMode(12, INPUT_PULLUP);

  interval = 200;

}

void loop()

{

  unsigned long ctime;

  int i;

  ctime = millis();

  if (digitalRead(11))

  {

      interval--;

      if (interval == 0)

          interval = 1;

  }

  if (digitalRead(12))

  {

      interval++;

      if (interval == 1000)

          interval = 1000;

  }

  if (ctime - ptime >= interval)

  {

     Serial.println(interval);

     ptime = ctime;

     for (i = 0; i < NUM_LEDS; i++)

        digitalWrite(i + 2, LOW);

     digitalWrite(position + 2, HIGH);

     position = position + 1;

     if (position > NUM_LEDS - 1)

     {

        position = 0;

     }

  }

  delay(10);

}