Neopixel code not working on Adafruit Feather board

Question

I have connected a single neopixel to my Adafruit Feather board, running Arduino software.

The power pin is connected to 3V on the Feather. The data-in pin is connected to pin 15 on the Feather.

As soon as power is connected, the light shows blue. But uploading any program has no effect whatsoever. The Neopixel won't respond to anything.

How can I use a Neopixel on the Adafruit Feather?

#include <Adafruit_NeoPixel.h>
#ifdef __AVR__
#include <avr/power.h>
#endif

#define PIN 15
#define NUMPIXELS 1

Adafruit_NeoPixel pixels = Adafruit_NeoPixel(NUMPIXELS, PIN, NEO_GRB + NEO_KHZ800);

void setup() {
  Serial.begin(9600);
  pixels.begin();
}

void loop() {
  Serial.println("RED");
  pixels.setPixelColor(PIN, pixels.Color(255, 0, 0));
  pixels.show();
  delay(1000);
  Serial.println("GREEN");
  pixels.setPixelColor(PIN, pixels.Color(0, 255, 0));
  pixels.show();
  delay(1000);
}

The neopixel and the Feather board

Answer 1

Pin 15 is the serial RX pin which connects to the USB port so you should not use it. From the Feather pinouts page about pins 15,16 : "These are connected through to the CP2104 USB-to-Serial converter so they should not be connected to or used unless you're super sure you want to because you will also be getting the USB traffic on these!"

So try another pin and it should work.