int t = 150;   // one unit of time in milliseconds

void setup() {
  pinMode(13, OUTPUT);  // LED pin is OUTPUT
}

void dot() {
  digitalWrite(13, HIGH);  delay(1*t);  digitalWrite(13, LOW);  delay(1*t);
}

void dash() {
  digitalWrite(13, HIGH);  delay(3*t);  digitalWrite(13, LOW);  delay(1*t);
}

void letter() {
  delay(2*t); // plus one unit from end of dot/dash = 3 units
}

void word() {
  delay(6*t); // plus one unit from end of dot/dash = 7 units
}

// Scan PATTERN and send a dot for every '.' or a dash for every '-'.
// Any other character generates an inter-letter pause.
// Generate an inter-word pause at the end of the string.
void sendMorse(char *pattern)
{
  int i = 0;   // index into string
  while (0 != pattern[i]) {
    int c = pattern[i];      // current character
    if      ('.' == c) dot();
    else if ('-' == c) dash();
    else               letter();
    i = i+1;
  }
  word();
}

void loop() {
  sendMorse("... --- ...");
}