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.
2026-08-09 21:14:55 +00:00
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+/*
+ * JoystickBridge.ino  —  Arduino Uno <-> Godot (ArduinoGodot/Main.gd)
+ *
+ * Talks plain serial lines to the UDP<->serial bridge process, which forwards
+ * telemetry to Godot on UDP 4242 and relays LED commands from UDP 4243.
+ *
+ * PROTOCOL (must match Main.gd)
+ *   OUT (Uno -> host):  "x,y,btn\n"   raw 10-bit ADC, e.g. "512,498,1"
+ *                       btn = 1 when the stick's push-button is pressed.
+ *   IN  (host -> Uno):  "L1" = LED on, "L0" = LED off  (newline optional)
+ *
+ * WIRING (KY-023 2-axis analog joystick + external LED)
+ *   Joystick  +5V / VCC  -> 5V
+ *   Joystick  GND        -> GND
+ *   Joystick  VRx        -> A0
+ *   Joystick  VRy        -> A1
+ *   Joystick  SW         -> D2   (uses internal pull-up; pressed = LOW)
+ *
+ *   LED:  D13 -> 220 ohm resistor -> LED anode (+, long leg)
+ *         LED cathode (-, short leg) -> GND
+ *   (D13 is also the Uno's onboard LED, so it flashes during every upload —
+ *    a free "is this pin alive" check. 220-330 ohm keeps it near ~15 mA.)
+ */
+
+const uint8_t PIN_VRX = A0;   // joystick X axis
+const uint8_t PIN_VRY = A1;   // joystick Y axis
+const uint8_t PIN_SW  = 2;    // joystick push-button (active LOW)
+const uint8_t PIN_LED = 13;   // external LED through a 220 ohm resistor (also onboard LED)
+
+const unsigned long BAUD      = 115200;  // must match the bridge process
+const unsigned long SEND_MS   = 16;      // ~60 Hz telemetry
+
+unsigned long lastSend = 0;
+char cmdBuf[8];
+uint8_t cmdLen = 0;
+
+void setup() {
+  Serial.begin(BAUD);
+  pinMode(PIN_SW, INPUT_PULLUP);
+  pinMode(PIN_LED, OUTPUT);
+  digitalWrite(PIN_LED, LOW);
+}
+
+void loop() {
+  handleCommands();
+
+  unsigned long now = millis();
+  if (now - lastSend >= SEND_MS) {
+    lastSend = now;
+    int x = analogRead(PIN_VRX);           // 0..1023
+    int y = analogRead(PIN_VRY);           // 0..1023
+    int btn = (digitalRead(PIN_SW) == LOW) // pull-up: LOW == pressed
+              ? 1 : 0;                     // Godot wants 1 = pressed
+
+    // "x,y,btn\n"
+    Serial.print(x);
+    Serial.print(',');
+    Serial.print(y);
+    Serial.print(',');
+    Serial.println(btn);
+  }
+}
+
+// Parse newline-terminated commands. Recognizes "L1" / "L0".
+void handleCommands() {
+  while (Serial.available() > 0) {
+    char c = Serial.read();
+    if (c == '\n' || c == '\r') {
+      if (cmdLen >= 2 && cmdBuf[0] == 'L') {
+        digitalWrite(PIN_LED, cmdBuf[1] == '1' ? HIGH : LOW);
+      }
+      cmdLen = 0;
+    } else if (cmdLen < sizeof(cmdBuf) - 1) {
+      cmdBuf[cmdLen++] = c;
+    } else {
+      cmdLen = 0;  // overflow guard: drop the runt line
+    }
+  }
+}