Controlling a LED using arduino serial monitor

Arduino Serial Communication

A Serial communication is a method of transmitting data as a train of 1s and 0s, i.e. only one bit for a clock cycle of binary coded data. Or one bit at a time, sequentially on a communication channel. It is a contrast to parallel communication, whereas in parallel system multiple bits are sent through several parallel paths. In a parallel system number of bits transmitted per clock is equal to the number of parallel paths. That is, a 4-bit channel can transmit any of the 16 binary states for a single clock cycle.

In a serial communication to transfer a byte, the data is transferred as a sequence of 8 bits as one by one. Each bit is either high state 1s or low state 0s.

In Arduino boards, the serial connection can be made either via serial port (type B USB) or by digital pins 0 (RX) and 1 (TX). An Arduino IDE includes a serial monitor, a built-in terminal to communicate with an Arduino board.

You can open the serial monitor by,

Press ctrl+shift+M

Tools/Serial Monitor

Or click the magnifier icon in the top right corner of the Arduino IDE.

Serial controlled LED

void setup() {
  pinMode(13, OUTPUT);
  Serial.begin(9600);
}
void loop() {
  if (Serial.available() > 0) {
    char state = Serial.read();
    if (state == 'H' || state == 'h') {
      digitalWrite(13, HIGH);
      Serial.println("LED ON");
    }
    if (state == 'L' || state == 'l') {
      digitalWrite(13, LOW);
      Serial.println("LED OFF");
    }
  }
  delay(50);
}

void setup() {
  pinMode(13, OUTPUT);
  Serial.begin(9600);
}
void loop() {
  if (Serial.available() > 0) {
    char state = Serial.read();
    if (state == '1') {
      digitalWrite(13, HIGH);
      Serial.println("LED ON");
    }
    if (state == '0') {
      digitalWrite(13, LOW);
      Serial.println("LED OFF");
    }
  }
  delay(50);
}