Adafruit Gemma.

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
    Serial.begin(9600);
}

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

    //print the sensor value to serial
    Serial.println(sensor);
}

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();
  strip.show(); // 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);
      strip.show();
      delay(wait);
  }
}

// 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!

##ACTION!

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

Some problems I ran into:

The Embroidery hoop is completely necessary. I tried sewing without it and it was a mess.
When sewing the neo-pixels, the input & output of each pixel shouldn’t touch each other.
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.

Alisa Palson. ( )