WS2812B LED strip with Arduino Nano ESP32

A WS2812B strip on the Nano ESP32 uses the same Adafruit NeoPixel code as a classic Nano. Data goes from D6 through 330 Ω; power comes from a separate 5 V adapter, with the grounds joined.

One Nano ESP32 setting matters here: switch Tools → Pin Numbering to “By GPIO number (legacy)”, or the NeoPixel library fails to link. The sketch runs a rainbow at about 25 % brightness and prints which GPIO D6 is.

Wiring

Board quirks

• There is no 5V pin on the Nano ESP32, and VBUS is raw USB power. A strip needs its own 5 V supply; join only the grounds.
• Set Tools → Pin Numbering → “By GPIO number (legacy)” for this sketch. In the default “By Arduino pin” mode, Adafruit NeoPixel 1.15.5 fails to link with undefined reference to digitalPinToGPIONumber: its ESP32 driver is a C file and can’t call the core’s C++ pin-remap function.
• Keep writing D6 in code: in GPIO mode the D6 name still points at the D6 pad (it becomes GPIO9). Only bare numbers change meaning, so 6 would then be GPIO6 = the pad labelled D3.
• The data signal is 3.3 V — fine for a short wire into a 5 V strip. For long runs add a 74AHCT125 buffer.
• Don’t confuse the strip with the board’s own RGB LED: that one is a plain common-anode LED on LED_RED/GREEN/BLUE, not a WS2812.

Code

// WS2812B strip on an Arduino Nano ESP32.
// DIN → D6 through 330 Ω. Strip 5V/GND → its own 5 V supply; supply GND → Nano GND.
// Needs Tools → Pin Numbering → "By GPIO number (legacy)" (set in this sketch's profile):
// Adafruit NeoPixel's ESP32 driver is plain C and can't link to the core's pin-remap function,
// so the default "By Arduino pin" mode fails with "undefined reference to digitalPinToGPIONumber".
// Keep writing D6: in GPIO mode the D6 name still means the D6 pad (GPIO9).
#include <Adafruit_NeoPixel.h>

constexpr uint16_t COUNT = 30;
Adafruit_NeoPixel strip(COUNT, D6, NEO_GRB + NEO_KHZ800);

void setup() {
  Serial.begin(115200);
  uint32_t t0 = millis();
  while (!Serial && millis() - t0 < 3000) {}
  strip.begin();
  strip.setBrightness(60);
  strip.show();
  Serial.printf("WS2812B: %u LEDs on D6 (GPIO%u)\n", COUNT, D6);
}

void loop() {
  static uint16_t hue = 0;
  for (uint16_t i = 0; i < COUNT; i++) {
    strip.setPixelColor(i, strip.gamma32(strip.ColorHSV(hue + i * 65536UL / COUNT)));
  }
  strip.show();
  hue += 256;
  delay(20);
}

// WS2812B strip on an Arduino Nano ESP32.
// DIN → D6 through 330 Ω. Strip 5V/GND → its own 5 V supply; supply GND → Nano GND.
// Needs Tools → Pin Numbering → "By GPIO number (legacy)" (set in this sketch's profile):
// Adafruit NeoPixel's ESP32 driver is plain C and can't link to the core's pin-remap function,
// so the default "By Arduino pin" mode fails with "undefined reference to digitalPinToGPIONumber".
// Keep writing D6: in GPIO mode the D6 name still means the D6 pad (GPIO9).
#include <Adafruit_NeoPixel.h>

constexpr uint16_t COUNT = 30;
Adafruit_NeoPixel strip(COUNT, D6, NEO_GRB + NEO_KHZ800);

void setup() {
  Serial.begin(115200);
  uint32_t t0 = millis();
  while (!Serial && millis() - t0 < 3000) {}
  strip.begin();
  strip.setBrightness(60);
  strip.show();
  Serial.printf("WS2812B: %u LEDs on D6 (GPIO%u)\n", COUNT, D6);
}

void loop() {
  static uint16_t hue = 0;
  for (uint16_t i = 0; i < COUNT; i++) {
    strip.setPixelColor(i, strip.gamma32(strip.ColorHSV(hue + i * 65536UL / COUNT)));
  }
  strip.show();
  hue += 256;
  delay(20);
}

Library: Adafruit NeoPixel (Adafruit) — compiled with Adafruit NeoPixel 1.15.5.

Expected serial output

WS2812B: 30 LEDs on D6 (GPIO9)

WS2812B: 30 LEDs on D6 (GPIO9)

Common errors