Godot + Arduino series: companion project code

Self-contained project code for the "Godot Isn't Just for Games" series:
Arduino sketches, the Python serial<->UDP bridge, and the Godot 4 projects,
one folder per article.

godot-arduino-1-led-first-light/godot/ArduinoGodot/LedBasics.gd

@@ -0,0 +1,24 @@
+extends Control
+
+# Part 1 — the minimal round trip: a Godot button that toggles an LED on the
+# Arduino. Only the OUTBOUND (command) half of the link is used here; Part 2
+# adds inbound telemetry from the joystick.
+
+const COMMAND_ADDR := "127.0.0.1"
+const COMMAND_PORT := 4243
+
+@onready var led_button: Button = $Panel/LedButton
+
+var _udp_out := PacketPeerUDP.new()
+var _led_on := false
+
+func _ready() -> void:
+	# To SEND with PacketPeerUDP in Godot 4, use set_dest_address — NOT
+	# connect_to_host, which is for receiving and silently drops outbound packets.
+	_udp_out.set_dest_address(COMMAND_ADDR, COMMAND_PORT)
+	led_button.pressed.connect(_on_led_pressed)
+
+func _on_led_pressed() -> void:
+	_led_on = not _led_on
+	_udp_out.put_packet(("L1" if _led_on else "L0").to_utf8_buffer())
+	led_button.text = "LED: ON" if _led_on else "LED: OFF"