Install the IDE & Blink: Your First Upload

Learning Goals 5 min

By the end of this lesson you will be able to:

1. Download and install the Arduino IDE 2.x on a Windows, macOS or Linux computer.
2. Connect the Arduino UNO over USB and select the correct Board and Port from the Tools menu.
3. Upload the Blink sketch onto a real board and watch the on-board LED flash once per second.

Warm-Up 10 min

Last lesson we toured the Arduino UNO board and learned that a microcontroller is a tiny brain that does one focused job. Today we wake the brain up.

Quick-fire puzzle

Two things have changed in the sketch below compared to the classic Blink. What do you think they do?

void setup() {
  pinMode(LED_BUILTIN, OUTPUT);
}

void loop() {
  digitalWrite(LED_BUILTIN, HIGH);
  delay(200);
  digitalWrite(LED_BUILTIN, LOW);
  delay(200);
}

New Concept 20 min

The big idea — from screen to chip

The Arduino IDE (Integrated Development Environment) is the app you use to write Arduino sketches. Think of it like a kitchen: you write the recipe (your sketch), the IDE turns the recipe into something the chip can actually eat (called compiling), and the upload button serves that meal onto the board over the USB cable.

Three steps happen behind the scenes every time you press upload:

• Compile — your readable sketch is translated into machine code the ATmega328P understands.
• Upload — the IDE sends that machine code down the USB cable to the board.
• Run — the board resets and starts running your sketch from the first line of setup().

Where the buttons are in the IDE

Open the Arduino IDE 2.x. The most important controls live in the top-left corner and the Tools menu:

Every sketch has these two functions

void setup() {
  // runs ONCE when the board powers on or resets
}

void loop() {
  // runs OVER and OVER, forever
}

Why it matters

Uploading code is the moment when "letters on a screen" become "things happening in the real world". This is the difference between programming a website and programming an Arduino — what you write tonight, you can hold in your hand tomorrow.

Worked Example 20 min

Together with your teacher, walk through these exact steps. By the end of the walkthrough every student should have the on-board LED blinking.

1. Open the Arduino IDE. Wait for it to finish starting up.
2. File → New Sketch — a fresh window appears with empty setup() and loop().
3. Plug the UNO into your computer with the USB cable. A green power LED should light up on the board.
4. From the top board dropdown choose Arduino UNO.
5. From the port list choose the USB port the board is plugged into (it will be labelled COMx on Windows or /dev/cu.usbmodem… on macOS).
6. Replace the empty sketch with the sketch below.
7. Press the Verify tick — the Output panel should say Done compiling.
8. Press the Upload arrow — the orange RX and TX LEDs on the board flicker for a few seconds.
9. Watch the orange L LED. It should now blink once per second.

// Blink — your first uploaded sketch
const int LED_PIN = 13;

void setup() {
  pinMode(LED_PIN, OUTPUT);
}

void loop() {
  digitalWrite(LED_PIN, HIGH);
  delay(1000);
  digitalWrite(LED_PIN, LOW);
  delay(1000);
}

What the board does once the upload finishes:

On-board L LED: on for 1 second, off for 1 second, forever.

Step 5 — see the timing before you change it

Uploading takes a few seconds each time, so it pays to know what a change will look like before you make it. Drag the two sliders below and watch the LED. The sketch underneath the sliders is exactly the one you just uploaded, with your two numbers filled in.

void setup() {
  pinMode(13, OUTPUT);
}

void loop() {
  digitalWrite(13, HIGH);
  delay(1000);
  digitalWrite(13, LOW);
  delay(1000);
}

Find the timing you want here first, then type those two numbers into the IDE and upload once.

What changed since last lesson? Nothing in the code — this is the same Blink sketch from ARD-L01-01. The difference is you have just uploaded it onto a real chip for the first time.

Basic 7 min

For each task, edit your Blink sketch, press Upload and watch the on-board LED. Do not move on until the LED actually does what the task asks.

void setup() {
  pinMode(13, OUTPUT);
}

void loop() {
  digitalWrite(13, HIGH);
  delay(1000);
  digitalWrite(13, LOW);
  delay(1000);
}

Challenge 1 7 min

void setup() {
  pinMode(13, OUTPUT);
}

void loop() {
  // blink twice quickly, then wait, then repeat
}

Challenge 2 6 min

void setup() {
  pinMode(13, OUTPUT);
}

void loop() {
  digitalWrite(13, HIGH);
  delay(500);
  digitalWrite(13, LOW);
  delay(500)
}

Challenge 3 15 min

Bring your ARD-L01-01 invention to life

Pull out the paper design of the smarter everyday object you sketched for last lesson's Extra Mission. Type in the Part 2 sketch you wrote on paper (or write one now). It should make the on-board LED simulate one output from your design:

• If your output is a buzzer that beeps every 5 seconds, blink the LED every 5 seconds.
• If your output is a motor that runs for 2 seconds when triggered, flash the LED for 2 seconds then off forever.
• If your output is a status indicator, use a long blink for "OK" and a fast double-blink for "alert".

Upload the sketch and demo it to a partner without telling them which invention it is.

It works if your partner can describe back to you what the LED behaviour represents in your invention.

Recap 5 min

You wrote your first uploaded sketch. The Arduino IDE compiled it into machine code, sent it down the USB cable, and the board ran it the moment it finished resetting. From now on, every lesson ends with code running on real hardware.

Arduino IDE

The free app you write, compile and upload Arduino sketches in.

Compile

Translate the sketch into machine code the microcontroller can run.

Upload

Send the compiled machine code over USB onto the board.

Port

The name your computer gives the USB connection — e.g. COM3 on Windows or /dev/cu.usbmodem14101 on macOS.

Sketch file (.ino)

The file extension the IDE saves your code in. Each sketch lives in its own folder.

Extra Mission 5 min

Part 1 — Design a one-light status code

Many devices talk to you with just one small light. A phone charger, a wireless speaker, a smoke alarm. Pick one device like this, real or invented. On paper, design the light code it should use.

Your design must include:

• The device's name and its one job.
• At least three states it needs to show, such as "charging", "full" and "error".
• A blink pattern for each state, with the on-time and off-time in milliseconds.
• A reason each pattern is easy to tell apart from the others.

Part 2 — Make it

Turn each state into its own Blink sketch for the on-board LED. Use only pinMode, digitalWrite and delay. Save them with clear names, such as status-charging. Upload each one and check the LED matches your design.

Bring back next class: your paper design, the saved sketches, and a screenshot of the Output panel showing Done uploading.