CircuitPython Code

If you haven't already, follow this guide to preparing the Trinket M0, including updating it with the latest version of CircuitPython.

After prepping the Trinket M0 to run CircuitPython we'll also need to add a NeoPixel library. This guide tells you how, as well as providing a good primer on using NeoPixels on the Trinket M0 with CircuitPython.

Installing NeoPixel Library

Download the latest adafruit-circuitpython-bundle-xxxx.zip (or newer) from the releases directory and then unzip it somewhere easy to find, such as your desktop. Then, copy the neopixel.mpy file to your CIRCUITPY's lib directory on the Trinket M0.

Finally, if you had a neopixel.py file that was already in that same lib directory you can delete it (the mpy is a compressed version)

Saving CircuitPython Code

Once you've got things working, you can edit the main.py file on the Trinket M0 to adjust what it actually does. No need for a software IDE, complaining tools, or flashing the chip -- when you code with CircuitPython all you need is a text editor. Edit the code, save it to the Trinket M0, and it immediately runs!

Below is side and front code that will change the color of the NeoPixel strip. 

Side Animation

# Adafruit Trinket+NeoPixel animation for Daft Punk-inspired helmet.
# Contains some ATtiny85-specific stuff; won't run as-is on Uno, etc.

# Operates in HSV (hue, saturation, value) colorspace rather than RGB.
# Animation is an interference pattern between two waves; one controls
# saturation, the other controls value (brightness).  The wavelength,
# direction, speed and type (square vs triangle wave) for each is randomly
# selected every few seconds.  Hue is always linear, but other parameters
# are similarly randomized.

import random
import board
import neopixel
from analogio import AnalogIn

n_leds = 29             # number of LEDs per horn
led_pin = board.D0      # which pin your pixels are connected to

# initialize neopixel strip
pixels = neopixel.NeoPixel(led_pin, n_leds, brightness=1, auto_write=False)
count = 1               # countdown to next animation change

# Gamma-correction table
gamma = [
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1,
    1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 2, 2, 2, 2, 2, 2,
    2, 3, 3, 3, 3, 3, 3, 3, 4, 4, 4, 4, 4, 5, 5, 5,
    5, 6, 6, 6, 6, 7, 7, 7, 7, 8, 8, 8, 9, 9, 9, 10,
    10, 10, 11, 11, 11, 12, 12, 13, 13, 13, 14, 14, 15, 15, 16, 16,
    17, 17, 18, 18, 19, 19, 20, 20, 21, 21, 22, 22, 23, 24, 24, 25,
    25, 26, 27, 27, 28, 29, 29, 30, 31, 32, 32, 33, 34, 35, 35, 36,
    37, 38, 39, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 50,
    51, 52, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 66, 67, 68,
    69, 70, 72, 73, 74, 75, 77, 78, 79, 81, 82, 83, 85, 86, 87, 89,
    90, 92, 93, 95, 96, 98, 99, 101, 102, 104, 105, 107, 109, 110,
    112, 114, 115, 117, 119, 120, 122, 124, 126, 127, 129, 131, 133,
    135, 137, 138, 140, 142, 144, 146, 148, 150, 152, 154, 156, 158,
    160, 162, 164, 167, 169, 171, 173, 175, 177, 180, 182, 184, 186,
    189, 191, 193, 196, 198, 200, 203, 205, 208, 210, 213, 215, 218,
    220, 223, 225, 228, 231, 233, 236, 239, 241, 244, 247, 249, 252,
    255
]

# initialize 3D list
wave = [0] * 5, [0] * 5, [0] * 5

wave_type = 0   # 0 = square wave, 1 = triangle wave
value_frame = 1 # start-of-frame value
value_pixel = 2 # pixel-to-pixel value
inc_frame = 3   # frame-to-frame increment
inc_pixel = 4   # pixel-to-pixel inc

wave_h = 0      # hue
wave_s = 1      # saturation
wave_v = 2      # brightness

# Random number generator is seeded from an unused 'floating'
# analog input - this helps ensure the random color choices
# aren't always the same order.
pin = AnalogIn(board.A0)
random.seed(pin.value)
pin.deinit()

# generate a non-zero random number for frame and pixel increments
def nz_random():
    random_number = 0

    while random_number <= 0:
        random_number = random.randint(0,15) - 7

    return random_number

while True:

    w = i = n = s = v = r = g = b = v1 = s1 = 0

    if count <= 0:                                  # time for new animation
        count = 250 + random.randint(0,250)         # effect run for 5-10 sec.

        for w in range(3):                          # three waves (H,S,V)
            wave[w][wave_type] = random.randint(0,2)# square vs triangle
            wave[w][inc_frame] = nz_random()        # frame increment
            wave[w][inc_pixel] = nz_random()        # pixel increment
            wave[w][value_pixel] = wave[w][value_frame]

        wave[wave_s][inc_pixel] *= 16               # make saturation & value
        wave[wave_v][inc_pixel] *= 16               # blinkier along strip

    else:                                           # continue animation
        count -= 1
        for w in range(3):
            wave[w][value_frame] += wave[w][inc_frame]
            wave[w][value_pixel] = wave[w][value_frame]

    # Render current animation frame.  COGNITIVE HAZARD: fixed point math.
    for i in range(n_leds):                             # for each LED along strip...
        # Coarse (8-bit) HSV-to-RGB conversion, hue first:
        n = (wave[wave_h][value_pixel] % 43) * 6   # angle within sextant

        sextant = wave[wave_h][value_pixel] / 43        # sextant number 0-5

        # R to Y
        if sextant == 0:
            r = 255
            g = n
            b = 0
        # Y to G
        elif sextant == 1:
            r = 254 - n
            g = 255
            b = 0
        # G to C
        elif sextant == 2:
            r = 0
            g = 255
            b = n
        # C to B
        elif sextant == 3:
            r = 0
            g = 254 - n
            b = 255
        # B to M
        elif sextant == 4:
            r = n
            g = 0
            b = 255
        # M to R
        else:
            r = 255
            g = 0
            b = 254 - n

        # Saturation = 1-256 to allow >>8 instead of /255
        s = wave[wave_s][value_pixel]

        if wave[wave_s][wave_type]:     # triangle wave?
            if s & 0x80:                # downslope
                s = (s & 0x7F) << 1
                s1 = 256 - s
            else:                       # upslope
                s = s<<1
                s1 = 1 + s
                s = 255 - s
        else:
            if s & 0x80:                # square wave
                s1 = 256                # 100% saturation
                s = 0
            else:                       # 0% saturation
                s1 = 1
                s = 255

        # Value (brightness) = 1-256 for similar reasons
        v = wave[wave_v][value_pixel]

        # value (brightness) = 1-256 for similar reasons
        if wave[wave_v][wave_type]:     # triangle wave?
            if v & 0x80:                # downslope
                v1 = 64 - ((v & 0x7F) << 1)
            else:                       # upslope
                v1 = 1 + (v << 1)
        else:
            if v & 0x80:                # square wave; on/off
                v1 = 256
            else:
                v1 = 1

        # gamma rgb values
        gr = ((((r * s1) >> 8) + s) * v1) >> 8
        gg = ((((g * s1) >> 8) + s) * v1) >> 8
        gb = ((((b * s1) >> 8) + s) * v1) >> 8

        # gamma rgb indices range check
        if -256 < gr < 256:
            r = gamma[gr]

        if -256 < gg < 256:
            g = gamma[gg]

        if -256 < gb < 256:
            b = gamma[gb]

        pixels[i] = (r, g, b)

        # update wave values along length of strip (values may wrap, is OK!)
        for w in range(3):
            wave[w][value_pixel] += wave[w][inc_pixel]

    pixels.show()

Copy the above "Side Animation" code, and then paste it into a new text document in your favorite text/coding editor. Then, save it to your Trinket M0's CIRCUITPY drive as main.py

Front Animation

# Fiery demon horns (rawr!) for Adafruit Trinket/Gemma.
# Adafruit invests time and resources providing this open source code,
# please support Adafruit and open-source hardware by purchasing
# products from Adafruit!

import board
import neopixel
from analogio import AnalogIn
# pylint: disable=global-statement

try:
    import urandom as random
except ImportError:
    import random

# /\  ->   Fire-like effect is the sum_total of multiple triangle
# ____/  \____  waves in motion, with a 'warm' color map applied.
n_horns = 1             # number of horns
led_pin = board.D0      # which pin your pixels are connected to
n_leds = 30             # number of LEDs per horn
frames_per_second = 50  # animation frames per second
brightness = 0          # current wave height
fade = 0                # Decreases brightness as wave moves
pixels = neopixel.NeoPixel(led_pin, n_leds, brightness=1, auto_write=False)
offset = 0

# Coordinate space for waves is 16x the pixel spacing,
# allowing fixed-point math to be used instead of floats.
lower = 0       # lower bound of wave
upper = 1       # upper bound of wave
mid = 2         # midpoint (peak) ((lower+upper)/2)
vlower = 3      # velocity of lower bound
vupper = 4      # velocity of upper bound
intensity = 5   # brightness at peak

y = 0
brightness = 0
count = 0

# initialize 3D list
wave = [[0] * 6] * 6, [[0] * 6] * 6, [[0] * 6] * 6, [[0] * 6] * 6, [[0] * 6] * 6, [[0] * 6] * 6

# Number of simultaneous waves (per horn)
n_waves = len(wave)

# Gamma-correction table
gamma = [
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1,
    1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 2, 2, 2, 2, 2, 2,
    2, 3, 3, 3, 3, 3, 3, 3, 4, 4, 4, 4, 4, 5, 5, 5,
    5, 6, 6, 6, 6, 7, 7, 7, 7, 8, 8, 8, 9, 9, 9, 10,
    10, 10, 11, 11, 11, 12, 12, 13, 13, 13, 14, 14, 15, 15, 16, 16,
    17, 17, 18, 18, 19, 19, 20, 20, 21, 21, 22, 22, 23, 24, 24, 25,
    25, 26, 27, 27, 28, 29, 29, 30, 31, 32, 32, 33, 34, 35, 35, 36,
    37, 38, 39, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 50,
    51, 52, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 66, 67, 68,
    69, 70, 72, 73, 74, 75, 77, 78, 79, 81, 82, 83, 85, 86, 87, 89,
    90, 92, 93, 95, 96, 98, 99, 101, 102, 104, 105, 107, 109, 110,
    112, 114, 115, 117, 119, 120, 122, 124, 126, 127, 129, 131, 133,
    135, 137, 138, 140, 142, 144, 146, 148, 150, 152, 154, 156, 158,
    160, 162, 164, 167, 169, 171, 173, 175, 177, 180, 182, 184, 186,
    189, 191, 193, 196, 198, 200, 203, 205, 208, 210, 213, 215, 218,
    220, 223, 225, 228, 231, 233, 236, 239, 241, 244, 247, 249, 252,
    255
]


def random_wave(he, wi):
    wave[he][wi][upper] = -1                                  # Always start below head of strip
    wave[he][wi][lower] = -16 * (3 + random.randint(0,4))     # Lower end starts ~3-7 pixels back
    wave[he][wi][mid] = (wave[he][wi][lower]+ wave[he][wi][upper]) / 2
    wave[he][wi][vlower] = 3 + random.randint(0,4)            #  Lower end moves at ~1/8 to 1/pixels
    wave[he][wi][vupper] = wave[he][wi][vlower]+ random.randint(0,4) # Upper end moves a bit faster
    wave[he][wi][intensity] = 300 + random.randint(0,600)

def setup():
    global fade

    # Random number generator is seeded from an unused 'floating'
    # analog input - this helps ensure the random color choices
    # aren't always the same order.
    pin = AnalogIn(board.A0)
    random.seed(pin.value)
    pin.deinit()

    for he in range(n_horns):
        for wi in range(n_waves):
            random_wave(he, wi)

    fade = 233 + n_leds / 2

    if fade > 233:
        fade = 233

setup()

while True:

    h = w = i = r = g = b = 0
    x = 0

    for h in range(n_horns):                # For each horn...
        x = 7
        sum_total = 0
        for i in range(n_leds):             # For each LED along horn...
            x += 16
            for w in range(n_waves):        # For each wave of horn...
                if (x < wave[h][w][lower]) or (x > wave[h][w][upper]):
                    continue                # Out of range
                if x <= wave[h][w][mid]:    # Lower half of wave (ramping up peak brightness)
                    sum_top = wave[h][w][intensity] * (x - wave[h][w][lower])
                    sum_bottom = (wave[h][w][mid] - wave[h][w][lower])
                    sum_total += sum_top /  sum_bottom
                else:                       # Upper half of wave (ramping down from peak)
                    sum_top = wave[h][w][intensity] * (wave[h][w][upper] - x)
                    sum_bottom = (wave[h][w][upper] - wave[h][w][mid])
                    sum_total += sum_top / sum_bottom

            sum_total = int(sum_total)          # convert from decimal to whole number

            # Now the magnitude (sum_total) is remapped to color for the LEDs.
            # A blackbody palette is used - fades white-yellow-red-black.
            if sum_total < 255:                 # 0-254 = black to red-1
                r = gamma[sum_total]
                g = b = 0
            elif sum_total < 510:               # 255-509 = red to yellow-1
                r = 255
                g = gamma[sum_total - 255]
                b = 0
            elif sum_total < 765:               # 510-764 = yellow to white-1
                r = g = 255
                b = gamma[sum_total - 510]
            else:                               # 765+ = white
                r = g = b = 255
            pixels[i] = (r, g, b)

    for w in range(n_waves):                    # Update wave positions for each horn
        wave[h][w][lower] += wave[h][w][vlower] # Advance lower position
        if wave[h][w][lower] >= (n_leds * 16):  # Off end of strip?
            random_wave(h, w)                   # Yes, 'reboot' wave
        else:                                   # No, adjust other values...
            wave[h][w][upper] += wave[h][w][vupper]
            wave[h][w][mid] = (wave[h][w][lower] + wave[h][w][upper]) / 2
            wave[h][w][intensity] = (wave[h][w][intensity] * fade) / 256 # Dimmer

    pixels.show()

Copy the above "Front Animation" code, and then paste it into a new text document in your favorite text/coding editor. Then, save it to your Trinket M0's CIRCUITPY drive as main.py

This guide was first published on Sep 04, 2014. It was last updated on Sep 04, 2014. This page (CircuitPython Code) was last updated on Nov 13, 2019.