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 to 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 “main.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).
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
import board
import neopixel
try:
import urandom as random # for v1.0 API support
except ImportError:
import random
numpix = 17 # Number of NeoPixels
pixpin = board.D1 # Pin where NeoPixels are connected
strip = neopixel.NeoPixel(pixpin, numpix)
minAlpha = 0.1 # Minimum brightness
maxAlpha = 0.4 # Maximum brightness
alpha = (minAlpha + maxAlpha) / 2 # Start in middle
alphaDelta = 0.008 # Amount to change brightness each time through loop
alphaUp = True # If True, brightness increasing, else decreasing
strip.fill([255, 0, 0]) # Fill red, or change to R,G,B of your liking
while True: # Loop forever...
if random.randint(1, 5) == 5: # 1-in-5 random chance
alphaUp = not alphaUp # of reversing direction
if alphaUp: # Increasing brightness?
alpha += alphaDelta # Add some amount
if alpha >= maxAlpha: # At or above max?
alpha = maxAlpha # Limit to max
alphaUp = False # and switch direction
else: # Else decreasing brightness
alpha -= alphaDelta # Subtract some amount
if alpha <= minAlpha: # At or below min?
alpha = minAlpha # Limit to min
alphaUp = True # and switch direction
strip.brightness = alpha # Set brightness to 0.0 to 1.0
strip.write() # and issue data to LED strip
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.
Page last edited January 14, 2025
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