Arduino Serial Monitor Echo: Wiring, Code and Simulator

To build this Arduino Serial Monitor Echo project you need an Arduino Uno and nothing but the board itself. Just the board and the serial port. It answers whatever you type, in capitals. Make the 0 connections in the wiring table, upload the Arduino C++ code, and type into the serial monitor and press Enter. The Arduino sends it back in upper case.

Open this circuit in the free Arduino Uno simulator

Parts list

Qty	Part	What it does
1	Arduino Uno	the microcontroller board

Wiring

No wiring: this project uses only the Arduino Uno.

Step by step

Open the simulator. Open the BitForBytes Embedded Lab in your browser and start from the Arduino Uno. No install or account is needed.
Add the parts. Add nothing but the board itself from the parts palette.
Paste the Arduino C++ code. Paste the Arduino C++ code below into the code editor.
Run it. Press Run. Type into the serial monitor and press Enter. The Arduino sends it back in upper case.

Arduino C++ code

// Serial echo: type in the serial monitor and the Arduino answers.
// Letters come back in upper case, so you can see the board did the work.
void setup() {
  Serial.begin(9600);
  Serial.println("Hello from the Arduino! Type something:");
}

void loop() {
  if (Serial.available() > 0) {
    char c = Serial.read();
    if (c >= 'a' && c <= 'z') c = c - 'a' + 'A';
    Serial.write(c);
  }
}

What to try

Type into the serial monitor and press Enter. The Arduino sends it back in upper case.

Frequently asked questions

How do I wire the Serial Monitor Echo project on an Arduino Uno?

No extra wiring is needed: it uses only the Arduino Uno itself.

What parts do I need for this Arduino project?

An Arduino Uno and nothing but the board itself.

Can I simulate this Arduino project online for free?

Yes. The BitForBytes Embedded Lab runs this exact circuit and Arduino C++ code in your browser for free, with no install and no hardware. The sketch is compiled with the real Arduino toolchain and runs on an emulated ATmega328P.

What does the code do?

Just the board and the serial port. It answers whatever you type, in capitals.