ATTiny Sketch for Homemade Hardware

sketch_apr01a.ino

const float FACTOR = 1.05946; // One semitone
float freq = 440;

const int BUTTON_UP = 3;
const int BUTTON_DOWN = 4;
const int SPEAKER = 0;

bool up_pressed = false;
bool down_pressed = false;

void setup() {
  pinMode(BUTTON_UP, INPUT);
  pinMode(BUTTON_DOWN, INPUT);
  pinMode(SPEAKER, OUTPUT);

  tone(SPEAKER, freq);
}

void loop() {
  bool freq_changed = false;
  if (!up_pressed && digitalRead(BUTTON_UP) == HIGH) {
    up_pressed = true;
  }
  if (up_pressed && digitalRead(BUTTON_UP) == LOW) {
    up_pressed = false;
    freq *= FACTOR;
    freq_changed = true;
  }
  if (!down_pressed && digitalRead(BUTTON_DOWN) == HIGH) {
    down_pressed = true;
  }
  if (down_pressed && digitalRead(BUTTON_DOWN) == LOW) {
    down_pressed = false;
    freq /= FACTOR;
    freq_changed = true;
  }

  if (freq_changed) {
    noTone(SPEAKER);
    tone(SPEAKER, freq); 
  }
}