Home > Arduino Sketch, Exploring Ideas > Serial Commands to Arduino ( LED control )

Serial Commands to Arduino ( LED control )

Serial_LED_control A small sketch to show how to implement a command menu using the Serial Monitor of the Arduino IDE. In this example the switch statement is used to identify the received command and execute the corresponding action.

— Command list: —

? -> Print this HELP

a -> LED On  “activate”

d -> LED Off “deactivate”

s -> LED     “status”


/*Serial_LED_02.ino  Arduining 4 May 2015
Controlling the LED in pin 13 with the Serial Monitor.
--- Command list: ---
? -> Print this HELP 
a -> LED On  "activate"
d -> LED Off "deactivate"
s -> LED     "status" 

Example using the switch statement.
#define LED 13          // Pin 13 is connected to the LED
char rxChar= 0;         // RXcHAR holds the received command.

//=== function to print the command list:  ===========================
void printHelp(void){
  Serial.println("--- Command list: ---");
  Serial.println("? -> Print this HELP");  
  Serial.println("a -> LED On  \"activate\"");
  Serial.println("d -> LED Off \"deactivate\"");
  Serial.println("s -> LED     \"status\"");  
//---------------- setup ---------------------------------------------
void setup(){
  Serial.begin(9600);   // Open serial port (9600 bauds).
  pinMode(LED, OUTPUT); // Sets pin 13 as OUTPUT.
  Serial.flush();       // Clear receive buffer.
  printHelp();          // Print the command list.

//--------------- loop ----------------------------------------------- 
void loop(){
  if (Serial.available() >0){          // Check receive buffer.
    rxChar = Serial.read();            // Save character received. 
    Serial.flush();                    // Clear receive buffer.
  switch (rxChar) {
    case 'a':
    case 'A':                          // If received 'a' or 'A':
	if (digitalRead(LED) == LOW){        // If LED is Off:
          digitalWrite(LED,HIGH);      // Turn On the LED.
          Serial.println("LED turned On");
        else Serial.println("LED already On!");

    case 'd':
    case 'D':                          // If received 'd' or 'D':
	if (digitalRead(LED) == HIGH){       // If LED is On:
          digitalWrite(LED,LOW);       // Turn Off the LED.
          Serial.println("LED turned Off");
        else Serial.println("LED already Off!");
    case 's':
    case 'S':                          // If received  's' or 'S':
	if (digitalRead(LED) == HIGH)        // Read LED status.
          Serial.println("LED status: On");
        else Serial.println("LED status: Off");
    case '?':                          // If received a ?:
        printHelp();                   // print the command list.
      Serial.println("' is not a command!");
// End of the Sketch.

  1. nazimkenan
    May 17, 2015 at 8:54 PM

    Great! Thank you for sharing this with us. Descriptions like your help newbies like me to get a better understanding of arduining.

    Two things I noticed: you mixed ab the keystrokes “d”, “D”, “s”, “S” in your comments, I think.

    Greetings from Germany. Keep up.

    • May 17, 2015 at 9:08 PM

      Thanks nazimkenan, corrected.

  2. Frannek
    January 14, 2016 at 3:27 AM


    i have a question. Is it possible to change the input into a Byte command?

  3. Frannek
    January 14, 2016 at 3:33 AM

    Hello, is it possible to change the “case” into a byte?

  4. M Arslan
    May 8, 2016 at 5:29 AM

    great work!!!!

    i want to ask is there any way that if i press a and “LED turned on” is written for some time and than only min menu appears ……. i mean it returns to main menu???

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