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 tothe 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).
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 Phil Burgess for Adafruit Industries
#
# SPDX-License-Identifier: MIT
#
import time
import board
import neopixel
try:
import urandom as random # for v1.0 API support
except ImportError:
import random
numpix = 24 # Number of NeoPixels
pixpin = board.D0 # Pin where NeoPixels are connected
strip = neopixel.NeoPixel(pixpin, numpix, brightness=0.3)
mode = 0 # Current animation effect
offset = 0 # Position of spinner animation
color = [255, 0, 0] # RGB color - red
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.write() # 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 wheels
# A little trick here: pixels are processed in groups of 8
# (with 2 of 8 on at a time), NeoPixel rings are 24 pixels
# (8*3) and 16 pixels (8*2), so we can issue the same data
# to both rings and it appears correct and contiguous
# (also, the pixel order is different between the two ring
# types, so we get the reversed motion on #2 for free).
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.write() # 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
# Rotate color R->G->B
color = [color[2], color[0], color[1]]
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.
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