Getting started with Gemma

The adafruit gemma is an small arduino made for wearable electronics.

Unfortunately, it is not supported in the Arduino IDE currently, but you can download a standalone IDE to work with or modify you’re current Arduino IDE.

I wanted to make a skirt that lights up with movement, so I used an Adafruit Gemma, 7 neo-pixels, a ton of conductive thread, a 9v coin cell battery, and a piezo film sensor.

####FIRST If you don’t have the Arduino IDE, you can download it here

I’d also recommend reading about the basics and the pinouts of the Gemma.

##Lights Connect the neopixels together using alligator clips (or if you have a strip they’re already connected). Each neopixel needs a connection to power, ground, and the previous/next neo pixel.

When you’re connecting the neo-pixels to each other, make sure you’re following the arrows. Those show what direction your data is traveling.

The neopixels have example code you can use to test your lights.

##Sensor To set up the sensor, you just have to instantiate the variable, set that varible to read the analog data outputed by the sensor

//puts sensor into global scope
int sensor;

void setup(){

void loop(){
    //sets sensor equal to value of sensor
    sensor = analogRead(1);

You don’t have any serial output with the gemma, so I used an Arduino Uno to quickly test the sensor, and to figure out what the range of values are.

int sensor;

void setup(){
    //open serial communication

void loop(){
    sensor = analogRead(1);

    //print the sensor value to serial

Doing this, I found out that the sensors output was a range between 0 to 1023. In order to get the values of that range to correlate to the 0 to 255 for the neopixels I used Arduino’s map function.

#include <Adafruit_NeoPixel.h>

#define PIN 1
#define PIXELS 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(PIXELS, PIN, NEO_GRB + NEO_KHZ800);

int sensor;

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

void loop() {
  sensor = analogRead(1);
  sensor = map(sensor, 0, 1023, 0, 255);

  colorWipe(strip.Color(random(sensor), random(sensor), random(sensor)), 50);

// Fill the dots one after the other with a color
void colorWipe(uint32_t c, uint8_t wait) {
  for(uint16_t i=0; i< strip.numPixels(); i++) {
      strip.setPixelColor(i, c);;

// Input a value 0 to 255 to get a color value.
// The colours are a transition r - g - b - back to r.
uint32_t Wheel(byte WheelPos) {
  if(WheelPos < 85) {
   return strip.Color(WheelPos * 3, 255 - WheelPos * 3, 0);
  } else if(WheelPos < 170) {
   WheelPos -= 85;
   return strip.Color(255 - WheelPos * 3, 0, WheelPos * 3);
  } else {
   WheelPos -= 170;
   return strip.Color(0, WheelPos * 3, 255 - WheelPos * 3);

And that’s all there is to the programming part.

Now, time to connect things!


I personally followed this tutorial to sew the neopixels into the skirt.

Some problems I ran into:

  1. The Embroidery hoop is completely necessary. I tried sewing without it and it was a mess.
  2. When sewing the neo-pixels, the input & output of each pixel shouldn’t touch each other.
  3. The power/ground bus thread should be reaaaallllyyy long, for my project, it was about 1.5 ft long, and I was running short near the end.