Adafruit NeoPixel cyclic color example

adafruit_neopixel_cyclic_color.ino

//
// For more detail, see tutorial below:
// https://learn.adafruit.com/adafruit-neopixel-uberguide/arduino-library
//

#include <Adafruit_NeoPixel.h>

// Arduino Pin No.
#define PIN 6
 
// Parameter 1 = number of pixels in strip
// Parameter 2 = pin number (most are valid)
// Parameter 3 = pixel type flags, add together as needed:
//   NEO_KHZ800  800 KHz bitstream (most NeoPixel products w/WS2812 LEDs)
//   NEO_KHZ400  400 KHz (classic 'v1' (not v2) FLORA pixels, WS2811 drivers)
//   NEO_GRB     Pixels are wired for GRB bitstream (most NeoPixel products)
//   NEO_RGB     Pixels are wired for RGB bitstream (v1 FLORA pixels, not v2)
Adafruit_NeoPixel strip = Adafruit_NeoPixel(4, PIN, NEO_GRB + NEO_KHZ800);

void setup() {
  strip.begin();
  strip.show(); // Initialize all pixels to 'off'
}

int t = 0;

int tcol(int t, int span) {
  span = (span + 1) * 500;
  float sig = sin(t * 3.14159 / float(span)) / 2.0 + .5;
  sig = sig * sig;
  return int(sig * 255) % 256;
}

void loop() {
  int n = strip.numPixels();

  for (int i = 0; i < n; i++) {
    strip.setPixelColor(i, tcol(t, i % 3), tcol(t, (i + 1) % 3), tcol(t, (i + 2) % 3));
  }

  strip.show();
  t++;
}