Arduino UNO R3
Getting Started Guide

Use the correct cable

Use the USB-A to USB-B cable included with your board. The USB-B end has a square-ish connector that plugs into the board. Some cheap USB cables are charge-only (2 wires inside) — use a data cable. The one in the box is always correct.

Check the indicator lights when connected

When plugged in, your board has small LED indicator lights near the USB port. Their exact color may vary between board models (some boards have blue/red, others have green/orange) — what matters is whether they light up:

Download Arduino IDE 2 (free)

Go to arduino.cc/en/software → and download for your platform. Always download Arduino IDE 2.x (latest version).

Install on your platform

Windows: Run the .exe installer → accept all defaults.

macOS: Open the .dmg → drag Arduino IDE to Applications. If macOS says "unidentified developer" → right-click the app → Open.

Linux: Download the .AppImage → right-click → Properties → Permissions → check "Allow executing as program." Then double-click to launch. Alternatively use the .zip → run install.sh.

Raspberry Pi: Run sudo apt-get install arduino or download the Linux ARM 32-bit AppImage.

Launch Arduino IDE

Open from Start Menu (Windows), Applications (macOS), or terminal (Linux). First launch may take 30–60 seconds indexing libraries. When you see the editor with a blank sketch — you're ready.

Android — ArduinoDroid app (no PC needed)

If you're uploading sketches directly from an Android phone, you do not need Arduino IDE installed on a computer. Instead use the ArduinoDroid app:

1. Install ArduinoDroid from the Google Play Store (~₹350 / ~$4 USD one-time). This is a full Arduino IDE port for Android with a built-in compiler.
2. On first launch, ArduinoDroid will download the compiler toolchain (~300 MB) — do this on Wi-Fi.
3. Connect your board via a USB OTG adapter (USB-C to USB-A, or Micro-USB to USB-A). ArduinoDroid will request permission to access the USB device — tap Allow.
4. Open or write your sketch → tap the Board selector → choose Arduino Uno → tap Upload ↑.

Select Board Type

Menu: Tools → Board → Arduino AVR Boards → Arduino Uno. It must say "Arduino Uno" — not Mega, Nano, or Leonardo.

Select the Port

Go to Tools → Port and select your board's port:

Open Blink example

In Arduino IDE: File → Examples → 01.Basics → Blink. A new editor window opens with the complete code.

Read the code — here's what it means

// Blink — the "Hello World" of Arduino
// Turns the built-in LED on for 1 second, then off for 1 second

// ── setup() runs ONCE when the board first powers on ─────────
void setup() {
  // LED_BUILTIN is a shortcut for pin 13 (the on-board LED)
  pinMode(LED_BUILTIN, OUTPUT);    // Set pin 13 as an output
}

// ── loop() repeats FOREVER after setup() finishes ────────────
void loop() {
  digitalWrite(LED_BUILTIN, HIGH);  // Turn LED ON  (5V on pin 13)
  delay(1000);                       // Wait 1000ms = 1 second
  digitalWrite(LED_BUILTIN, LOW);   // Turn LED OFF (0V on pin 13)
  delay(1000);                       // Wait 1 second
}                                    // Back to top of loop()

Upload the sketch

Click the Upload → button (right-arrow in toolbar) or press Ctrl+U (Win/Linux) / Cmd+U (Mac). You'll see:

• Status bar: "Compiling sketch…" (takes ~5–15 seconds)
• TX/RX LEDs on board blink rapidly during upload transfer
• Status bar: "Done uploading." ✅

Watch the L LED blink 🎉

The orange L LED on your board blinks: 1 second ON, 1 second OFF. If you see this — your board is fully working!