What is Serial?

Serial communication lets Arduino send and receive data to/from your computer through the USB cable. Open the Serial Monitor in Arduino IDE (Tools → Serial Monitor or Ctrl+Shift+M).

Sending Data (Arduino → Computer)

void setup() {
    Serial.begin(9600);  // Start serial at 9600 baud
}

void loop() {
    Serial.println("Hello from Arduino!");
    Serial.print("Temperature: ");
    Serial.println(25.5);
    delay(1000);
}

Receiving Data (Computer → Arduino)

int ledPin = 13;

void setup() {
    Serial.begin(9600);
    pinMode(ledPin, OUTPUT);
    Serial.println("Send '1' for ON, '0' for OFF");
}

void loop() {
    if (Serial.available() > 0) {
        char input = Serial.read();
        if (input == '1') {
            digitalWrite(ledPin, HIGH);
            Serial.println("LED is ON");
        } else if (input == '0') {
            digitalWrite(ledPin, LOW);
            Serial.println("LED is OFF");
        }
    }
}

Serial Plotter

Use Tools → Serial Plotter to visualize data as a graph in real-time!

void loop() {
    int sensorValue = analogRead(A0);
    Serial.println(sensorValue);  // Shows as graph!
    delay(50);
}

✅ Quick Quiz

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