GEMMA jewelry! The bitty board fits perfectly in the center of a NeoPixel ring for flashy hoop earrings or a charming pendant. Read on to build your own!
Before you get started, follow the Introducing GEMMA guide or Introducing Gemma M0 guide
Bill of materials (for one pendant-- double this for a pair of earrings):
If this is your first time using GEMMA, work through the Introducing GEMMA guide first; you need to customize some settings in the Arduino IDE. Once you have it up and running (test the 'blink' sketch), then follow the instructions on the following page for installing the NeoPixel library:
Plug in your circuit and load up the sketch below:
// SPDX-FileCopyrightText: 2017 Phillip Burgess for Adafruit Industries
//
// SPDX-License-Identifier: MIT
// Low power NeoPixel earrings example. Makes a nice blinky display
// with just a few LEDs on at any time...uses MUCH less juice than
// rainbow display!
#include <Adafruit_NeoPixel.h>
#define PIN 0
#define NUM_LEDS 16
Adafruit_NeoPixel pixels = Adafruit_NeoPixel(NUM_LEDS, PIN);
uint8_t mode = 0, // Current animation effect
offset = 0; // Position of spinner animation
uint32_t color = 0xFF8000; // Starting color = amber
uint32_t prevTime; // Time of last animation mode switch
void setup() {
pixels.begin();
pixels.setBrightness(60); // ~1/3 brightness
prevTime = millis(); // Starting time
}
void loop() {
uint8_t i;
uint32_t t;
switch(mode) {
case 0: // Random sparkles - just one LED on at a time!
i = random(NUM_LEDS); // Choose a random pixel
pixels.setPixelColor(i, color); // Set it to current color
pixels.show(); // Refresh LED states
// Set same pixel to "off" color now but DON'T refresh...
// it stays on for now...both this and the next random
// pixel will be refreshed on the next pass.
pixels.setPixelColor(i, 0);
delay(10); // 10 millisecond delay
break;
case 1: // Spinny wheel (4 LEDs on at a time)
for(i=0; i<NUM_LEDS; i++) { // For each LED...
uint32_t c = 0; // Assume pixel will be "off" color
if(((offset + i) & 7) < 2) { // For each 8 pixels, 2 will be...
c = color; // ...assigned the current color
}
pixels.setPixelColor(i, c); // Set color of pixel 'i'
}
pixels.show(); // Refresh LED states
delay(50); // 50 millisecond delay
offset++; // Shift animation by 1 pixel on next frame
break;
// More animation modes could be added here!
}
t = millis(); // Current time in milliseconds
if((t - prevTime) > 8000) { // Every 8 seconds...
mode++; // Advance to next animation mode
if(mode > 1) { // End of modes?
mode = 0; // Start over from beginning
color >>= 8; // And change color
if(!color) color = 0xFF8000; // preiodically reset to amber
}
pixels.clear(); // Set all pixels to 'off' state
prevTime = t; // Record the time of the last mode change
}
}
GEMMA M0 boards can run CircuitPython — a different approach to programming compared to Arduino sketches. In fact, CircuitPython comes factory pre-loaded on GEMMA M0. If you’ve overwritten it with an Arduino sketch, or just want to learn the basics of setting up and using CircuitPython, this is explained in the Adafruit GEMMA M0 guide.
Below is CircuitPython code that works similarly (though not exactly the same) as the Arduino sketch shown on a prior page. To use this, plug the GEMMA M0 into USB…it should show up on your computer as a small flash drive…then edit the file “code.py” with your text editor of choice. Select and copy the code below and paste it into that file, entirely replacing its contents (don’t mix it in with lingering bits of old code). When you save the file, the code should start running almost immediately (if not, see notes at the bottom of this page).
This project is designed to work with RGB NeoPixel rings, not RGBW. The code will not work with RGBW.
If GEMMA M0 doesn’t show up as a drive, follow the GEMMA M0 guide link above to prepare the board for CircuitPython.
# SPDX-FileCopyrightText: 2017 Phillip Burgess for Adafruit Industries
#
# SPDX-License-Identifier: MIT
# NeoPixel earrings example. Makes a nice blinky display with just a
# few LEDs on at any time...uses MUCH less juice than rainbow display!
import time
from rainbowio import colorwheel
import board
import neopixel
import adafruit_dotstar
try:
import urandom as random # for v1.0 API support
except ImportError:
import random
dot = adafruit_dotstar.DotStar(board.APA102_SCK, board.APA102_MOSI, 1, brightness=0.2)
dot[0] = (0, 0, 0)
numpix = 16 # Number of NeoPixels (e.g. 16-pixel ring)
pixpin = board.D0 # Pin where NeoPixels are connected
strip = neopixel.NeoPixel(pixpin, numpix, brightness=.3, auto_write=False)
mode = 0 # Current animation effect
offset = 0 # Position of spinner animation
hue = 0 # Starting hue
color = colorwheel(hue & 255) # hue -> RGB color
prevtime = time.monotonic() # Time of last animation mode switch
while True: # Loop forever...
if mode == 0: # Random sparkles - lights just one LED at a time
i = random.randint(0, numpix - 1) # Choose random pixel
strip[i] = color # Set it to current color
strip.show() # Refresh LED states
# Set same pixel to "off" color now but DON'T refresh...
# it stays on for now...bot this and the next random
# pixel will be refreshed on the next pass.
strip[i] = [0, 0, 0]
time.sleep(0.008) # 8 millisecond delay
elif mode == 1: # Spinny colorwheel (4 LEDs on at a time)
for i in range(numpix): # For each LED...
if ((offset + i) & 7) < 2: # 2 pixels out of 8...
strip[i] = color # are set to current color
else:
strip[i] = [0, 0, 0] # other pixels are off
strip.show() # Refresh LED states
time.sleep(0.04) # 40 millisecond delay
offset += 1 # Shift animation by 1 pixel on next frame
if offset >= 8:
offset = 0
# Additional animation modes could be added here!
t = time.monotonic() # Current time in seconds
if (t - prevtime) >= 8: # Every 8 seconds...
mode += 1 # Advance to next mode
if mode > 1: # End of modes?
mode = 0 # Start over from beginning
hue += 80 # And change color
color = colorwheel(hue & 255)
strip.fill([0, 0, 0]) # Turn off all pixels
prevtime = t # Record time of last mode change
This code requires the neopixel.py library. A factory-fresh board will have this already installed. If you’ve just reloaded the board with CircuitPython, create the “lib” directory and then download neopixel.py from Github.
This guide was first published on Sep 18, 2013. It was last updated on Sep 18, 2013.
