Arduino code to read a button & blink a normal LED and a Neopixel on XIAO ESP32C6 w/ Adafruit Button BFF

xiao_esp32c6_blink_button.ino

// xiao_esp32c6_blink_button.ino -- Read a button and blink a normal LED and a Neopixel
//                                  Demo'd on a XIAO ESP32C6 w/ Adafruit IoT Button BFF or NeoKey BFF
// 23 Sep 2025 - @todbot
// Useful links:
// https://wiki.seeedstudio.com/xiao_esp32c6_getting_started/
// https://github.com/espressif/arduino-esp32/blob/master/variants/XIAO_ESP32C6/pins_arduino.h
// https://files.seeedstudio.com/wiki/SeeedStudio-XIAO-ESP32C6/XIAO-ESP32-C6_v1.0_SCH_PDF_24028.pdf

#include <Adafruit_NeoPixel.h>

// XIAO ESP32C6 built-ins
#define LED_PIN LED_BUILTIN
//#define BUTTON_PIN 9  // built-in button, aka BOOT

// XIAO ESP32C6 w/ Adafruit keyswitch BFF w/neopixel
#define BUTTON_PIN    D2    // aka GPIO2, aka A2
#define NEOPIXEL_PIN  D3    // aka GPIO21, aka A3 
Adafruit_NeoPixel neopixel(1, NEOPIXEL_PIN, NEO_GRB + NEO_KHZ800);

void setup() {
  pinMode(LED_PIN, OUTPUT);
  pinMode(BUTTON_PIN, INPUT_PULLUP);
  neopixel.begin(); 
}

uint32_t last_time;
bool blink_state = false;

void loop() {
  int buttonval = digitalRead(BUTTON_PIN); // button is active-LOW
  int blink_time = buttonval ? 500 : 100; //  blink 5x faster on button push

  if( millis() - last_time > blink_time ) { 
    last_time = millis();
    blink_state = !blink_state;  // toggle our state
    neopixel.setPixelColor(0, blink_state ? 0x330033: 0x000000);
    neopixel.show();
    digitalWrite(LED_PIN, !blink_state); // turn the LED on/off (XIAO ESP32C6 LED is wired active-LOW)
  }

  delay(1);  // just in case to give some cycles to other things 
}