The Arduino code presented below works equally well on all versions of GEMMA: v1, v2 and M0. But if you have an M0 board, consider using the CircuitPython code on the next page of this guide, no Arduino IDE required!

With the circuit prototyped and the GEMMA connected to your computer, it's time to upload the NeoPixie Dust Bag sketch. This program randomly twinkles the NeoPixels and changes color each time you touch the capsense switch.

Click the "Copy Code" link at the top of the code block, then create a new sketch in the Adafruit Arduino IDE by clicking File > New. Then, paste the code by clicking Edit > Paste in the Arduino menu. Upload the code to your GEMMA by pressing the reset button on the GEMMA, waiting for the onboard red LED to blink, and then clicking File > Upload in the Arduino IDE.

Once the code has been uploaded, your NeoPixie Dust Bag will begin to twinkle in the traditional, golden pixie dust hue. Tap the capsense switch to change it to blue. Be amazed and overjoyed! Then, keep trying out the different color shifts, or, modify the code to create your own colors.

//  NeoPixie Dust Bag by John Edgar Park
//     No fairy costume is complete without a glowing pixie dust bag. 
//     This one uses a touch sensor to cycle through colors on the beautifully twinkling NeoPixel rings, 
//     controlled by the tiny Adafruit GEMMA microcontroller.
//     Build instructions:
//  Some code based upon Adafruit GEMMA earring code and Adafruit NeoPixel buttoncycler code

#include <Adafruit_NeoPixel.h>  //Include the NeoPixel library

#define NEO_PIN 0        // DIGITAL IO pin for NeoPixel OUTPUT from GEMMA
#define TOUCH_PIN 2      // DIGITAL IO pin for momentary touch sensor INPUT to GEMMA
#define PIXEL_COUNT 30   // Number of NeoPixels connected to GEMMA
#define DELAY_MILLIS 10  // delay between blinks, smaller numbers are faster 
#define DELAY_MULT 8     // Randomization multiplier on the delay speed of the effect
#define BRIGHT 100        // Brightness of the pixels, max is 255

// Parameter 1 = number of pixels in strip
// Parameter 2 = pin number on Arduino (most are valid)
// Parameter 3 = pixel type flags, add together as needed:
//   NEO_RGB     Pixels are wired for RGB bitstream (v1 FLORA pixels, not v2)
//   NEO_GRB     Pixels are wired for GRB bitstream, correct for neopixel stick (most NeoPixel products)
//   NEO_KHZ400  400 KHz bitstream (e.g. FLORA pixels)
//   NEO_KHZ800  800 KHz bitstream (e.g. High Density LED strip), correct for neopixel stick
Adafruit_NeoPixel pixels = Adafruit_NeoPixel(PIXEL_COUNT, NEO_PIN, NEO_GRB + NEO_KHZ800);

bool oldState = HIGH; //sets the initial variable for counting touch sensor button pushes
int showColor = 0;    //color mode for cycling

void setup() {
  pinMode(TOUCH_PIN, INPUT);    //Initialize touch sensor pin as input using external pull-up resistor
  pixels.setBrightness(BRIGHT);;                //Set all pixels to "off"

void loop() {
  int RColor = 100; //color (0-255) values to be set by cylcing touch switch, initially GOLD
  int GColor = 0 ;
  int BColor = 0 ;
       if (showColor==0) {//Garden PINK
         RColor = 242;
         GColor = 90;
         BColor = 255; 
       if (showColor==1) {//Pixie GOLD
         RColor = 255;
         GColor = 222;
         BColor = 30; 
       if (showColor==2) {//Alchemy BLUE
         RColor = 50;
         GColor = 255;
         BColor = 255; 
       if (showColor==3) {//Animal ORANGE
         RColor = 255;
         GColor = 100;
         BColor = 0; 
       if (showColor==4) {//Tinker GREEN
         RColor = 0;
         GColor = 255;
         BColor = 40; 
  int p = random(PIXEL_COUNT); //select a random pixel
  pixels.setPixelColor(p,RColor,GColor,BColor); //color value comes from cycling state of momentary switch;
  delay(DELAY_MILLIS * random(DELAY_MULT) ); //delay value randomized to up to DELAY_MULT times longer
  pixels.setPixelColor(p, RColor/10, GColor/10, BColor/10); //set to a dimmed version of the state color;
  pixels.setPixelColor(p+1, RColor/15, GColor/15, BColor/15); //set a neighbor pixel to an even dimmer value;
  //button check to cycle through color value sets
  bool newState = digitalRead(TOUCH_PIN); //Get the current button state
  // Check if state changed from high to low (button press).
  if (newState == LOW && oldState == HIGH) {
    // Short delay to debounce button.
    // Check if button is still low after debounce.
    newState = digitalRead(TOUCH_PIN);
    if (newState == LOW) {
      if (showColor > 4)
  // Set the last button state to the old state.
  oldState = newState;  
Keep your body parts away from the capacitive switch when the circuit is turning on so it can calibrate itself.

This guide was first published on Oct 22, 2014. It was last updated on Oct 22, 2014.

This page (Arduino Code) was last updated on Apr 18, 2021.

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