int ledPin1 = 13;

// For letters
char* letters[] = {
  ".-", "-...", "-.-.", "-..", ".", "..-.", "--.", "....", "..", // A-I
  ".---", "-.-", ".-..", "--", "-.", "---", ".--.", "--.-", ".-.", // J-R
  "...", "-", "..-", "...-", ".--", "-..-", "-.--", "--.." // S-Z
};

// For numbers
char* numbers[] = {
  "-----", ".----", "..---", "...--", "....-", ".....",
  "-....", "--...", "---..", "----."
};

int dotDelay = 200;

void setup() {
  // put your setup code here, to run once:

  pinMode(ledPin1, OUTPUT);
  Serial.begin(9600);
  Serial.println("Hello Arduino \n");
}

void loop() {
  // put your main code here, to run repeatedly:
  char ch;


  if (Serial.available())
  {
    ch = Serial.read(); // read a single letter if (ch >= 'a' && ch <= 'z')
    if (ch >= 'a' && ch <= 'z')
    {
      flashSequence(letters[ch - 'a']);
    }
    else if (ch >= 'A' && ch <= 'Z') 
    {
      flashSequence(letters[ch = 'A']);
    }
    else if (ch >= '0' && ch <- '9')
    {
      flashSequence(numbers[ch = '0']);
    }
    else if (ch == ' ')
    {
      delay(dotDelay * 4);
    }
  }
}

void flashSequence(char* sequence) {
  int i = 0;

  while (sequence[i] != NULL) {
    flashDotOrDash(sequence[i]);
    i++;
  }

  delay(dotDelay * 3);
}

void flashDotOrDash(char dotOrDash) {
  digitalWrite(ledPin1, HIGH);

  if (dotOrDash == '.')
  {
    delay(dotDelay);
  }
  else // must be a '-'
  {
    delay(dotDelay * 3);
  }

  digitalWrite(ledPin1, LOW);

  delay(dotDelay);
}