# Part 1 — Your First Arduino Round-Trip

Code for [*"Godot Isn't Just for Games: Your First Arduino Round-Trip"*](https://codebycandle.com/blog/godot-arduino-led-first-light).

A button in a Godot 4 scene reaches down a USB cable — through a Python-to-UDP
bridge — and lights a real LED on an Arduino Uno.

## Contents

```
arduino/
  LedBasics/LedBasics.ino   # reads L1/L0 off serial, drives the LED on D13
  bridge/bridge.py          # serial <-> UDP relay (run this, leave it running)
  bridge/ledtest.py         # quick standalone LED blink test (no Godot)
godot/
  ArduinoGodot/             # Godot 4 project: one styled toggle button
```

## Wiring

D13 → 220 Ω resistor → LED long leg (anode); LED short leg (cathode) → GND.
No breadboard? The Uno's onboard LED is already on D13.

## Run it

1. **Flash** `arduino/LedBasics/LedBasics.ino` to the Uno (Arduino IDE, 115200 baud).
2. **Bridge:** `pip install pyserial`, then `python arduino/bridge/bridge.py`. Leave it running.
3. **Godot:** open `godot/ArduinoGodot/` in Godot 4, press Play, click the button.

The bridge auto-detects the board and reconnects if the cable pops out.