For more advanced users, or if you want more control over colors and modes, Arduino using the FastLED library is a great way to go.  FastLED is a robust library with lots of fancy functions and lots of code samples to choose from.  If you want custom animations and color palettes, this is the top-of-the-line.

The code I've uploaded will cycle through 5 different color modes either automatically (changing every 60 seconds) or when you press the left button on the Circuit Playground Express.  The right button will turn the LEDs off.

Before You Start

If this is your first foray into the world of arduino-based microcontrollers, you'll need to install some software first. Head over to the Circuit Playground Lesson 0 guide for detailed installation and setup instructions.  

You'll only need to do all this once, so be a little patient if it seems like a lot!

FastLED Library

You will also need to install the FastLED library in Arduino (Sketch > Include Library > Manage Libraries...)

One other note:  if you're using FastLED with Circuit Playground Express, be sure to #include the Circuit Playground library FIRST and the FastLED library second, or you may run into problems.

Upload Code

Once you've got everything installed and your computer can talk to the Circuit Playground Express, it's time to upload the code.

Plug your Circuit Playground Express into your computer and select the Circuit Playground Express under Tools > Boards.  Then select the port identified as Circuit Playground Express.

Copy and paste this code into a new Arduino window and click "upload".

// SPDX-FileCopyrightText: 2013 FastLED
// SPDX-FileCopyrightText: 2018 Erin St Blaine for Adafruit Industries
// SPDX-License-Identifier: MIT

// Code by Erin St Blaine for, based on FastLED animations by Mark Kriegsman

#include <Adafruit_CircuitPlayground.h>
#include <FastLED.h>

// tell FastLED all about the Circuit Playground's layout

#define DATA_PIN     A1    //LED data on pin A1
#define NUM_LEDS    200   // total number of LEDs in your strip
#define COLOR_ORDER GRB  //  color order -- change this if your colors are coming out wrong

uint8_t brightness = 150;  // Set brightness level

int STEPS = 6;  //makes the rainbow colors more or less spread out
int NUM_MODES = 5;  // change this number if you add or subtract modes
int CYCLETIME = 60;  // number of seconds on each mode, for mode cycling

CRGB leds[NUM_LEDS];      // set up an LED array

CRGBPalette16 currentPalette;
TBlendType    currentBlending;

int ledMode = 0;       //Initial mode 
bool leftButtonPressed;
bool rightButtonPressed;

// SETUP -----------------------------------------------------
void setup() {
  FastLED.addLeds<WS2812B, DATA_PIN, COLOR_ORDER>(leds, NUM_LEDS).setCorrection( TypicalLEDStrip ); // Use this line if using neopixels
  currentBlending = LINEARBLEND;
  set_max_power_in_volts_and_milliamps(5, 5000);               // FastLED 2.1 Power management set at 5V, 5000mA


void loop()  {

  leftButtonPressed = CircuitPlayground.leftButton();
  rightButtonPressed = CircuitPlayground.rightButton();

  if (leftButtonPressed) {  //left button cycles through modes
    if (ledMode > NUM_MODES){
    if (rightButtonPressed) {  // on off button
 switch (ledMode) {
       case 0: modeCycle(); break;
       case 1: currentPalette = RainbowColors_p; rainbow(); break;
       case 2: currentPalette = OceanColors_p; rainbow(); break;                    
       case 3: currentPalette = LavaColors_p; rainbow(); break;   
       case 4: currentPalette = ForestColors_p; rainbow(); break;
       case 5: currentPalette = PartyColors_p; rainbow(); break;
       case 99: clearpixels(); break;
void clearpixels()
   for( int i = 0; i < NUM_LEDS; i++) {
   leds[i]= CRGB::Black;

void rainbow()
  static uint8_t startIndex = 0;
  startIndex = startIndex + 1; /* motion speed */

  FillLEDsFromPaletteColors( startIndex);;

//this bit is in every palette mode, needs to be in there just once
void FillLEDsFromPaletteColors( uint8_t colorIndex)
  for( int i = 0; i < NUM_LEDS; i++) {
    leds[i] = ColorFromPalette( currentPalette, colorIndex, brightness, currentBlending);
    colorIndex += STEPS;

int cycleMode=0;

void modeCycle()
   switch (cycleMode) {
       case 0: currentPalette = RainbowColors_p; rainbow(); break;
       case 1: currentPalette = OceanColors_p; rainbow(); break;                    
       case 2: currentPalette = LavaColors_p; rainbow(); break;   
       case 3: currentPalette = ForestColors_p; rainbow(); break;
       case 4: currentPalette = PartyColors_p; rainbow(); break;
       case 5: cycleMode=0; break;


If all goes well, the lights on the Circuit Playground will come on.  Press the right side button to turn the lights on and off.  Press the left side button to toggle between color modes.  

The initial mode will cycle through five different color modes, changing every 60 seconds.  Change this duration in the code with the CYCLETIME variable.  

The other modes use FastLEDs built in color palettes for a variety of different looks.

Add your own modes or customize the modes that are already there.  If you want to add your own color palettes, check out this Neopixel Parasol guide for ideas and instructions on how to do that with FastLED.

This guide was first published on Dec 11, 2018. It was last updated on Jul 09, 2024.

This page (Code with Arduino) was last updated on Jul 09, 2024.

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