int led = 13;  // led to use for output (13 is built-in)

int dit_delay = 500;           // length of a dit in ms
int dah_delay = dit_delay * 3; // length of a dah in ms

// dit() and dat() already include dit_delay
int letter_delay = dah_delay - dit_delay;

// letters already include letter delay
int word_delay   = dit_delay * 7 - letter_delay;

void dit() {
    Serial.print(".");

    // send a dit
    digitalWrite(led, HIGH);
    delay(dit_delay);

    digitalWrite(led, LOW);
    delay(dit_delay);
}

void dah() {
    Serial.print("-");
  
    // send a dah
    digitalWrite(led, HIGH);
    delay(dah_delay);

    digitalWrite(led, LOW);
    delay(dit_delay);
}

void pause_letter() {
   Serial.println("");
   delay(letter_delay);
}

void pause_word() {
   Serial.println("");
   delay(word_delay);
}

void morse_S() {
    dit(); dit(); dit();
    pause_letter();
}

void morse_I() {
    dit(); dit();
    pause_letter();
}

void morse_N() {
    dah(); dit();
    pause_letter();
}

void morse_K() {
    dah(); dit(); dah();
    pause_letter();
}

void morse_SINK() {
    morse_S(); morse_I(); morse_N(); morse_K();
    pause_word();
}

// send n in morse code
void morse_digit(int n) {
    Serial.print("morse_digit(");
    Serial.print(n);
    Serial.println(")...");

    if (n == 0) {
        dah(); dah(); dah(); dah(); dah();
    }
    if (n == 1) {
        dit(); dah(); dah(); dah(); dah();
    }
    if (n == 2) {
        dit(); dit(); dah(); dah(); dah();
    }
    if (n == 3) {
        dit(); dit(); dit(); dah(); dah();
    }
    if (n == 4) {
        dit(); dit(); dit(); dit(); dah();
    }
    if (n == 5) {
        dit(); dit(); dit(); dit(); dit();
    }
    if (n == 6) {
        dah(); dit(); dit(); dit(); dit();
    }
    if (n == 7) {
        dah(); dah(); dit(); dit(); dit();
    }
    if (n == 8) {
        dah(); dah(); dah(); dit(); dit();
    }
    if (n == 9) {
        dah(); dah(); dah(); dah(); dit();
    }
    pause_letter();
    
    Serial.print("morse_digit(");
    Serial.print(n);
    Serial.println(")...done");
}

void morse_number(int n) {
    Serial.print("morse_number(");
    Serial.print(n);
    Serial.println(")...");
  
    if (n >= 10) {
        morse_number(n / 10);
    }
    morse_digit(n % 10);

    Serial.print("morse_number(");
    Serial.print(n);
    Serial.println(")...done");
}

void setup() {
  // put your setup code here, to run once:
  
  // Configure LED as output
  pinMode(led, OUTPUT);
  
  // Use serial port as output
  Serial.begin(9600);
}

void loop() {
  // put your main code here, to run repeatedly: 
  morse_SINK();  
  morse_number(5024);
}