PotStep Tone Control

#define BUT 0
#define POT A0
#define BUZZ 10

#define UP 5
#define DOWN 4

void setup() {
  pinMode(BUT, INPUT_PULLUP);
  pinMode(UP, INPUT_PULLUP);
  pinMode(DOWN, INPUT_PULLUP);
  pinMode(POT, INPUT);
  pinMode(BUZZ, OUTPUT);
  //Serial.begin(9600);
}

boolean state = true;
boolean uState = true;
boolean dState = true;

boolean bTone = false;

int steps = 0;

void loop() {
  detectButtons();
  steps = limit(steps, 0, 20);
  int hz = map(analogRead(POT), 0, 1023, 400, 800);
  hz *= pow(2, steps/12.0);

  if (bTone) {
    tone(BUZZ, hz);
  } else {
    noTone(BUZZ);
  }

  //Serial.println(steps);
}

void detectButtons() {
  if ((digitalRead(BUT) == LOW) && state) {
    bTone = !bTone;
    state = false;
  } else if (digitalRead(BUT) == HIGH) {
    state = true;
  }

  if ((digitalRead(UP) == LOW) && uState) {
    steps++;
    uState = false;
  } else if (digitalRead(UP) == HIGH) {
    uState = true;
  }

  if ((digitalRead(DOWN) == LOW) && dState) {
    steps--;
    dState = false;
  } else if (digitalRead(DOWN) == HIGH) {
    dState = true;
  }
}

int limit(int a, int _min, int _max) {
  a = max(_min, a);
  a = min(a, _max);
  return a;
}