ESP32 RGB LED Pattern Controller

BuildWhat You Will Build

GoalsLearning Objectives

• Wire a common-cathode RGB LED.
• Use LEDC PWM on GPIO25/GPIO26/GPIO27.
• Debounce a button on GPIO14.
• Differentiate a single RGB LED from addressable NeoPixels.

PartsComponents List

• 📦ESP32 DevKit boardMain 3.3 V logic controller.
• 📦Common-cathode 4-pin RGB LEDShared cathode goes to GND.
• 📦Three 220 ohm resistorsOne per red, green, and blue channel.
• 📦Push buttonPattern select input to GND using INPUT_PULLUP.
• 📦Breadboard and jumper wiresFor low-voltage prototyping.

PartsBill of Materials

🔗Wiring

Common cathode goes to GND. Red, green, and blue anodes go through resistors to GPIO25, GPIO26, and GPIO27. Button connects GPIO14 to GND.

No separate electrical diagram is supplied. Use the connection table and wiring steps below; confirm the exact module pin labels before connecting power.

1. 1

   Unplug USB before wiring.

2. 2

   Connect the common cathode pin to GND.

3. 3

   Connect red through 220 ohm resistor to GPIO25.

4. 4

   Connect green through 220 ohm resistor to GPIO26.

5. 5

   Connect blue through 220 ohm resistor to GPIO27.

6. 6

   Connect one side of the button to GPIO14 and the other to GND.

GPIO Mapping

Circuit Explanation

Engineering Explanation

Libraries

• Arduino ESP32 coreClassic ESP32-WROOM DevKit (Arduino board: ESP32 Dev Module), Arduino-ESP32 3.x (3.0.0 or later). Uses the 3.x pin-based LEDC API; Arduino-ESP32 2.x requires the separately labeled legacy reference. Documentation reviewed; this sketch has not been compiled or hardware-tested in this batch. No external library is needed.

⌨️Code

Copy into Arduino IDE. Install any libraries noted in the component guides first.

// Classic ESP32 Dev Module; Arduino-ESP32 3.x (>= 3.0.0)
// ESP32 common-cathode RGB LED pattern controller
// Single low-power RGB LED, not an addressable strip.
const int RED_PIN = 25;
const int GREEN_PIN = 26;
const int BLUE_PIN = 27;
const int BUTTON_PIN = 14;

const int PWM_FREQ = 5000;
const int PWM_RES = 8;

int pattern = 0;
bool lastButton = HIGH;
unsigned long lastDebounceMs = 0;
unsigned long frameMs = 0;

void writeRgb(uint8_t r, uint8_t g, uint8_t b) {
  ledcWrite(RED_PIN, r);
  ledcWrite(GREEN_PIN, g);
  ledcWrite(BLUE_PIN, b);
}

void setupPwm() {
  if (!ledcAttach(RED_PIN, PWM_FREQ, PWM_RES) ||
      !ledcAttach(GREEN_PIN, PWM_FREQ, PWM_RES) ||
      !ledcAttach(BLUE_PIN, PWM_FREQ, PWM_RES)) {
    Serial.println("RGB PWM attachment failed");
    while (true) delay(1000);
  }
}

void setup() {
  Serial.begin(115200);
  setupPwm();
  pinMode(BUTTON_PIN, INPUT_PULLUP);
  writeRgb(255, 0, 0);
}

void loop() {
  bool button = digitalRead(BUTTON_PIN);
  if (button != lastButton && millis() - lastDebounceMs > 40) {
    lastDebounceMs = millis();
    lastButton = button;
    if (button == LOW) {
      pattern = (pattern + 1) % 3;
      Serial.printf("Pattern %d\n", pattern);
    }
  }

  unsigned long now = millis();
  if (now - frameMs < 20) return;
  frameMs = now;

  uint8_t phase = (now / 8) & 0xFF;
  if (pattern == 0) {
    writeRgb(255, 0, 0);
  } else if (pattern == 1) {
    writeRgb(phase, 255 - phase, 128);
  } else {
    int step = (now / 500) % 6;
    const uint8_t colors[6][3] = {{255,0,0},{255,80,0},{0,255,0},{0,255,255},{0,0,255},{160,0,255}};
    writeRgb(colors[step][0], colors[step][1], colors[step][2]);
  }
}

Code Explanation