CircuitPython code for a glowing SeaWing costume based on the Trinket M0 board

code.py

# mommy and daddy 10/18/24

import board
import time
import math

from digitalio import DigitalInOut, Direction, Pull
from adafruit_dotstar import DotStar
from neopixel_write import neopixel_write

# colored dotstar led on board (not neopixel)
color_led = DotStar(board.APA102_SCK, board.APA102_MOSI, 1)
color_led.brightness = 0.05

# basic little red LED near usb charger
led = DigitalInOut(board.LED)
led.direction = Direction.OUTPUT

# switch connecting D2 to GND
switch = DigitalInOut(board.D2)
switch.direction = Direction.INPUT
switch.pull = Pull.UP

# neopixel strip on D3
strip = DigitalInOut(board.D3)
strip.direction = Direction.OUTPUT

num_lights = 22
pixel_buffer = bytearray(3 * num_lights)

alpha = 0  # color blend
beta = 0  # activation blend
gamma = 15  # activation transition rate
last_t = 0
ticks = 0


def lerp(a, b, t):
    return int(a + (b - a) * t)


def shade_channel(light, channel):
    base_a = 1 - ((light - t * num_lights * 2) % num_lights) / num_lights
    base_value = lerp(base_grb[channel], base_grb[channel] // 2, base_a)
    signal_a = 1 - ((light + t * num_lights * 4) % num_lights) / num_lights
    signal_value = lerp(signal_grb[channel], signal_grb[channel] // 4, signal_a)
    q = light / num_lights
    return lerp(min(255, base_value + signal_value * beta), 0, q)


while True:
    ticks += 1
    ticks %= num_lights
    t = time.monotonic()
    dt = t - last_t
    last_t = t

    alpha = math.sin(2 * math.pi * (t % 1)) * 0.5 + 0.5

    target = int(not switch.value)
    beta = beta + (target - beta) * gamma * dt
    beta = min(1, max(0, beta))

    base_grb = [lerp(12, 6, alpha), lerp(0, 0, alpha), lerp(6, 12, alpha)]
    signal_grb = [lerp(64, 32, alpha), lerp(64, 64, alpha), lerp(128, 128, alpha)]

    subsample = 3
    for i in range(ticks % subsample, num_lights * 3, subsample):
        pixel_buffer[i] = shade_channel(i // 3, i % 3)

    neopixel_write(strip, pixel_buffer)
    led.value = not switch.value