Marine signalling light using the Morse symbols

//                      MARITIME SIGNALLING LIGHT SOFTWARE
//
//                     Tested with Arduino Uno and Nano Every
//
// The International Code of Signals (ICS) is an international system of signals and codes 
// for use by vessels to communicate important messages regarding safety of navigation and 
// related matters. Signals can be sent by flaghoist, signal lamp ("blinker"), flag 
// semaphore, radiotelegraphy, and radiotelephony. The International Code is the most 
// recent evolution of a wide variety of maritime flag signalling systems. 
//
// See International Code of Signals, 2005 ed. (IMO IA994E), IMO  International Maritime 
// Organization, 2005, ISBN 978-92-801-4198-6
//
// This program can be used for flashing light signalling by morse codes.
// You don't have to be familiar with morse code in order to send a message.
//
// You need an Arduino, a mosfet, signalling lamp and computer / or mobile phone with
// USB OTG cable and for example Kai Morich's (Gerhart-Hauptmann-Str. 13, 68766 Hockenheim, 
// Germany) "Serial USB Terminal" -program for Android phones from Google Play.
//
// I found no signalling lamp for my boat so I made it by myself.
//
// Jarmo Kiuru OH8JK - Oulu, Finland.

const int mosfet = 2; // The pin the mosfet is connected to.


void setup() {
    // Initialize digital pin as an output.
    pinMode(mosfet, OUTPUT);

}

void loop() {

    // Delays of morse code - you can adjust for your needs.
    const int dotMorse = 300; //A dot is one unit
    const int dashMorse = 900; //A dash is three units
    const int breakMorse = 300; //The space between same letter is one unit
    const int spaceletterMorse = 900; //The space between letters is three units
    const int breakwordsMorse = 2100; //The space between words is seven units

    String merkki = "";
    char lahete[] = "";
    char MorseCode[8] = "";

    // HOX! SMALL LETTERS 
    char LATIN_CHARACTERS[] = {
        // Numbers
        '0', '1', '2', '3', '4',
        '5', '6', '7', '8', '9',
        // Letters 
        'a', 'b', 'c', 'd', 'e', 
        'f', 'g', 'h', 'i', 'j', 
        'k', 'l', 'm', 'n', 'o', 
        'p', 'q', 'r', 's', 't', 
        'u', 'v', 'w', 'x', 'y', 'z', 
        // Special
        '.', '?', '@', ' '
    };

    //MORSE_CHARACTERS are all eight letters long filled with spaces at the end
    String MORSE_CHARACTERS[] = {
        // Numbers
        "-----   ", ".----   ", "..---   ", "...--   ", "....-   ",
        ".....   ", "-....   ", "--...   ", "---..   ", "----.   ", 
        // Letters
        ".-      ",    "-...    ",  "-.-.    ",  "-..     ", ".       ", 
        "..-.    ",  "--.     ",   "....    ",  "..      ",  ".---    ",
        "-.-     ",   ".-..    ",  "--      ",    "-.      ",  "---     ",
        ".--.    ",  "--.-    ",  ".-.     ",   "...     ",  "-       ",     
        "..-     ",   "...-    ",  ".--     ",   "-..-    ", "-.--    ",  "--..    ",
        // Special
        ".-.-.-  ", "..--..  ", ".--.-.  ", "        "
    };


  // This opens the serial port.
  Serial.begin(9600);
  delay(10);                        // Wait for a 1/100 second

  // Here the program get a character from the terminal via serial port.
  merkki = Serial.readString();
  delay(10);                        // Wait for a 1/100 second
  
  

  // This goes thru all latin characters and finds out what you have typed in.  
  for (int h=0; h < merkki.length(); h++) {
      merkki.toCharArray(lahete, merkki.length());
              for (int i=0; i < 40; i++) {

                    // This converts MORSE_CHARACTERS as an char array and place the array into variabel MorseCode.
                    MORSE_CHARACTERS[i].toCharArray(MorseCode, 8);
        
                    // When this if sentence finds a match to what you have typed in it sends it using the Morse code. 
                    if (LATIN_CHARACTERS[i] == lahete[h]) {
                    Serial.print("     ");
                    Serial.print(LATIN_CHARACTERS[i]);
                    Serial.print("     ");

                        for (int j=0; j < 8; j = j+1) {
      
                        if (MorseCode[j] == '-') {
                          digitalWrite(mosfet, HIGH);
                          Serial.print('-');
                          delay(dashMorse);
                          digitalWrite(mosfet, LOW);
                          delay(breakMorse);
                        }
                        else if (MorseCode[j] == '.') {
                          digitalWrite(mosfet, HIGH);
                          Serial.print('.');            
                          delay(dotMorse);
                          digitalWrite(mosfet, LOW);
                          delay(breakMorse);
                        }
                        else if (MorseCode[j] == ' ') {
                              
                              // If MorseCode's first character is space then it separates two words.
                              if (MorseCode[j] == ' ' && j == 0) {
                              digitalWrite(mosfet, LOW);
                              delay(breakwordsMorse);
                              }
                          
                          // All Morse symbols are eight character long and when the program finds first space
                          // it interrupts the for sentence. 
                          break; 
                        }
                        }
                          Serial.println();
                          delay(spaceletterMorse);
        }
  }
}
}