Teaching Arduino to Understand Humans — Morse Code Decoder with LED and Buzzer

1#define BUTTON_PIN 2
2#define LED_PIN 13
3#define buzz_pin 8
4
5unsigned long pressStart = 0;
6unsigned long releaseTime = 0;
7String morseBuffer = "";
8
9void setup() {
10  pinMode(BUTTON_PIN, INPUT);
11  pinMode(LED_PIN, OUTPUT);
12  pinMode(buzz_pin, OUTPUT);
13  digitalWrite(buzz_pin, HIGH);  // Buzzer OFF by default (active LOW)
14  Serial.begin(9600);
15  Serial.println("Morse Code Decoder Ready");
16}
17
18void loop() {
19  int buttonState = digitalRead(BUTTON_PIN);
20
21  // Button pressed
22  if (buttonState == HIGH && pressStart == 0) {
23    pressStart = millis();
24    digitalWrite(LED_PIN, HIGH);   // LED ON
25    digitalWrite(buzz_pin, LOW);   // Buzzer ON
26  }
27
28  // Button released
29  if (buttonState == LOW && pressStart != 0) {
30    unsigned long pressDuration = millis() - pressStart;
31    pressStart = 0;
32    digitalWrite(LED_PIN, LOW);    // LED OFF
33    digitalWrite(buzz_pin, HIGH);  // Buzzer OFF
34
35    if (pressDuration < 300) {
36      morseBuffer += ".";
37      Serial.print(".");
38    } else {
39      morseBuffer += "-";
40      Serial.print("-");
41    }
42    releaseTime = millis();
43  }
44
45  // Detect end of letter (1 second gap)
46  if (morseBuffer.length() > 0 && millis() - releaseTime > 1000) {
47    char letter = decodeMorse(morseBuffer);
48    Serial.print(" -> ");
49    Serial.println(letter);
50    morseBuffer = "";
51  }
52}
53
54char decodeMorse(String code) {
55  if (code == ".-")   return 'A';
56  if (code == "-...") return 'B';
57  if (code == "-.-.") return 'C';
58  if (code == "-..")  return 'D';
59  if (code == ".")    return 'E';
60  if (code == "..-.") return 'F';
61  if (code == "--.")  return 'G';
62  if (code == "....") return 'H';
63  if (code == "..")   return 'I';
64  if (code == ".---") return 'J';
65  if (code == "-.-")  return 'K';
66  if (code == ".-..") return 'L';
67  if (code == "--")   return 'M';
68  if (code == "-.")   return 'N';
69  if (code == "---")  return 'O';
70  if (code == ".--.") return 'P';
71  if (code == "--.-") return 'Q';
72  if (code == ".-.")  return 'R';
73  if (code == "...")  return 'S';
74  if (code == "-")    return 'T';
75  if (code == "..-")  return 'U';
76  if (code == "...-") return 'V';
77  if (code == ".--")  return 'W';
78  if (code == "-..-") return 'X';
79  if (code == "-.--") return 'Y';
80  if (code == "--..") return 'Z';
81  return '?';
82}