Day 1: Setup and First Sketch | Arduino in 5 Days

Arduino IDE and Board Setup

Download the Arduino IDE 2 from arduino.cc. Install it. Connect your Arduino Uno or Nano via USB. In Tools → Board, select 'Arduino Uno'. In Tools → Port, select the COM port (Windows) or /dev/cu.usbmodem... (macOS) or /dev/ttyACM0 (Linux). If Linux shows permission errors: sudo usermod -aG dialout $USER then log out and back in.

Sketch Structure

Every Arduino sketch has two functions. setup() runs once at power-on — initialize pins, serial port, and libraries here. loop() runs forever after setup — this is where your main logic lives. There is no main() — the Arduino framework wraps everything. The built-in LED is on pin 13 (constant LED_BUILTIN). pinMode(pin, OUTPUT) configures a pin. digitalWrite(pin, HIGH) sets it to 5V.

Serial Monitor for Debugging

Serial.begin(9600) in setup() opens a UART connection at 9600 baud. Serial.println(value) sends a line. Open the Serial Monitor (Ctrl+Shift+M) — it shows live output from the Arduino. This is your primary debugging tool. Use Serial.print() without newline for inline values, Serial.println() to add a newline.

cpp

// Arduino Blink with Serial feedback
// Upload to Arduino Uno/Nano via Arduino IDE

const int LED_PIN = LED_BUILTIN; // Pin 13
const int BLINK_INTERVAL = 500;  // milliseconds

void setup() {
  Serial.begin(9600);
  pinMode(LED_PIN, OUTPUT);
  Serial.println("Arduino started. Blinking LED...");
}

void loop() {
  digitalWrite(LED_PIN, HIGH);
  Serial.println("LED ON");
  delay(BLINK_INTERVAL);

  digitalWrite(LED_PIN, LOW);
  Serial.println("LED OFF");
  delay(BLINK_INTERVAL);
}

// ── Non-blocking blink (better practice) ────────────
// Use millis() instead of delay() so other code can run
unsigned long lastToggle = 0;
bool ledState = false;

void loop_nonblocking() {
  unsigned long now = millis();
  if (now - lastToggle >= BLINK_INTERVAL) {
    lastToggle = now;
    ledState = !ledState;
    digitalWrite(LED_PIN, ledState ? HIGH : LOW);
    Serial.print("LED: ");
    Serial.println(ledState ? "ON" : "OFF");
  }
  // Other code here runs every iteration without blocking
}

💡

Never use delay() in real projects — it blocks everything. Use millis() to track elapsed time and take action when enough time has passed. This lets the same loop handle multiple timers simultaneously.

📝 Day 1 Exercise

Blink Three LEDs at Different Rates

Wire 3 LEDs with 330Ω resistors to pins 9, 10, 11.
Implement non-blocking blink for each LED: 250ms, 500ms, 1000ms intervals using millis().
Add Serial output: print which LED toggled and at what millis() time.
Verify all three blink independently without blocking each other.
Add a 4th state: when all three are ON simultaneously, print 'SYNC' to serial.

Day 1 Summary

setup() runs once, loop() runs forever — this is the entire Arduino execution model
Use millis() not delay() for timing — delay() blocks the entire MCU
Serial.begin(9600) + Serial.println() is your debugging lifeline on embedded hardware
LED_BUILTIN (pin 13) has a built-in current-limiting resistor — external LEDs always need their own

Challenge

Implement a Morse code transmitter. Define a string message (e.g., 'SOS'). Encode dots (250ms on, 250ms off) and dashes (750ms on, 250ms off) with 500ms gap between letters. Use only millis() — no delay(). Print each symbol to Serial as it transmits.

Day 2: Digital I/O

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