Lesson 3: Buzzer Patterns

/*
  DIY KIT - Arduino UNO Sensor & Output Starter Kit
  Lesson 3 of 7: Buzzer Patterns

  WIRING (unplug the USB cable before you wire)
    Active buzzer module, using 3 male-to-female jumper wires:
      S (signal, may be labelled I/O or IN) -> UNO pin 6
      + (VCC)                               -> 5V
      - (GND)                               -> GND
    The LEDs and potentiometer from Lessons 1-2 can stay where they are.

  WHAT SHOULD HAPPEN
    The buzzer plays pattern 1 (slow beep), then 2 (fast alarm), then 3 (SOS),
    changing every 6 seconds. Open the Serial Monitor (9600 baud), type a
    number 0-3 and press Enter to choose a pattern yourself. 0 = silence.
*/

const int BUZZER_PIN = 6;

// Most modules beep when the pin is HIGH. If yours beeps in the gaps or
// all the time, change false to true and upload again.
const bool BUZZER_ACTIVE_LOW = false;

const unsigned long SLOW_ON_MS = 300, SLOW_OFF_MS = 700;  // pattern 1: slow warning
const unsigned long FAST_ON_MS = 80,  FAST_OFF_MS = 120;  // pattern 2: urgent alarm
const unsigned long DOT_MS     = 120, DASH_MS     = 360;  // pattern 3: SOS in Morse code
const unsigned long AUTO_CHANGE_MS = 6000;                // demo mode: next pattern every 6 s

int pattern = 1;                 // the pattern playing now (0-3)
bool demoMode = true;            // true until you type a number
bool newChoice = false;          // set when you type a number
unsigned long patternStarted = 0;

void buzzer(bool on) {
  if (BUZZER_ACTIVE_LOW) {
    digitalWrite(BUZZER_PIN, on ? LOW : HIGH);
  } else {
    digitalWrite(BUZZER_PIN, on ? HIGH : LOW);
  }
}

void announce() {
  Serial.print("Pattern ");
  Serial.print(pattern);
  if (pattern == 0)      Serial.println(": silence");
  else if (pattern == 1) Serial.println(": slow beep");
  else if (pattern == 2) Serial.println(": fast alarm");
  else                   Serial.println(": SOS");
  patternStarted = millis();
}

// Read anything typed in the Serial Monitor.
void readKeyboard() {
  while (Serial.available() > 0) {
    char c = Serial.read();          // one character at a time
    if (c >= '0' && c <= '3') {
      pattern = c - '0';             // the character '2' becomes the number 2
      demoMode = false;              // you chose: stop changing by itself
      newChoice = true;
      announce();
    }
  }
}

// Wait, but keep listening to the keyboard.
// Returns true if you typed a new pattern while waiting.
bool waitAndListen(unsigned long ms) {
  unsigned long start = millis();
  while (millis() - start < ms) {
    readKeyboard();
    if (newChoice) return true;
    delay(1);                        // a tiny pause before checking again
  }
  return false;
}

// One beep: on for onMs, then off for offMs. Returns true if interrupted.
bool beep(unsigned long onMs, unsigned long offMs) {
  buzzer(true);
  bool stop = waitAndListen(onMs);
  buzzer(false);
  if (stop) return true;
  return waitAndListen(offMs);
}

void playSOS() {
  for (int i = 0; i < 3; i++) if (beep(DOT_MS, DOT_MS)) return;   // S = . . .
  if (waitAndListen(DASH_MS)) return;
  for (int i = 0; i < 3; i++) if (beep(DASH_MS, DOT_MS)) return;  // O = - - -
  if (waitAndListen(DASH_MS)) return;
  for (int i = 0; i < 3; i++) if (beep(DOT_MS, DOT_MS)) return;   // S = . . .
  waitAndListen(1000);
}

void setup() {
  pinMode(BUZZER_PIN, OUTPUT);
  buzzer(false);
  Serial.begin(9600);
  Serial.println("Lesson 3: Buzzer Patterns - type 0, 1, 2 or 3 and press Enter");
  announce();
}

void loop() {
  newChoice = false;

  // Demo mode: move on to the next pattern every few seconds.
  if (demoMode && millis() - patternStarted > AUTO_CHANGE_MS) {
    pattern = pattern % 3 + 1;  // 1 -> 2 -> 3 -> 1
    announce();
  }

  if (pattern == 1)      beep(SLOW_ON_MS, SLOW_OFF_MS);
  else if (pattern == 2) beep(FAST_ON_MS, FAST_OFF_MS);
  else if (pattern == 3) playSOS();
  else {                 // pattern 0: silence
    buzzer(false);
    waitAndListen(100);
  }
}