from neopixel import Neopixel
from time import sleep

## Setup
NUM_LEDS = 16
LED_PIN = 6
pixels = Neopixel(NUM_LEDS, 0, LED_PIN, "GRB")

## Color Parameters
# Hue
hue_offset = 4096
# Brightness
min_brightness = 120
max_brightness = 255
breathing_speed = 10
brightness = max_brightness
brightness_up = False

## Loop
while True:
  for hue in range(0, 65535, 1000):

    # Breathe the brightness
    if brightness_up:
      brightness += breathing_speed
      if brightness >= max_brightness:
        brightness_up = False
    else:
      brightness -= breathing_speed
      if brightness <= min_brightness:
        brightness_up = True
    
    # Set the hues
    for led in range(NUM_LEDS):
      color = pixels.colorHSV(hue + (led * hue_offset), 128, brightness)
      pixels.set_pixel(led, color)

    pixels.show()
    sleep(0.05)


## Code for flashing the LEDs
# num_on_loops = 8
# num_off_loops = 1
# loop_count = 0

    # # Flash the brightness
    # if brightness is 255 and loop_count is num_on_loops:
    #   brightness = 0
    #   loop_count = 0
    # elif brightness is 0 and loop_count is num_off_loops:
    #   brightness = 255
    #   loop_count = 0
    # else:
    #   loop_count += 1

main.py

diagram.json

import array, time
from machine import Pin
import rp2

# PIO state machine for RGB. Pulls 24 bits (rgb -> 3 * 8bit) automatically
@rp2.asm_pio(sideset_init=rp2.PIO.OUT_LOW, out_shiftdir=rp2.PIO.SHIFT_LEFT, autopull=True, pull_thresh=24)
def ws2812():
    T1 = 2
    T2 = 5
    T3 = 3
    wrap_target()
    label("bitloop")
    out(x, 1)               .side(0)    [T3 - 1]
    jmp(not_x, "do_zero")   .side(1)    [T1 - 1]
    jmp("bitloop")          .side(1)    [T2 - 1]
    label("do_zero")
    nop().side(0)                       [T2 - 1]
    wrap()

# PIO state machine for RGBW. Pulls 32 bits (rgbw -> 4 * 8bit) automatically
@rp2.asm_pio(sideset_init=rp2.PIO.OUT_LOW, out_shiftdir=rp2.PIO.SHIFT_LEFT, autopull=True, pull_thresh=32)
def sk6812():
    T1 = 2
    T2 = 5
    T3 = 3
    wrap_target()
    label("bitloop")
    out(x, 1)               .side(0)    [T3 - 1]
    jmp(not_x, "do_zero")   .side(1)    [T1 - 1]
    jmp("bitloop")          .side(1)    [T2 - 1]
    label("do_zero")
    nop()                   .side(0)    [T2 - 1]
    wrap()


# Delay here is the reset time. You need a pause to reset the LED strip back to the initial LED
# however, if you have quite a bit of processing to do before the next time you update the strip
# you could put in delay=0 (or a lower delay)
#
# Class supports different order of individual colors (GRB, RGB, WRGB, GWRB ...). In order to achieve
# this, we need to flip the indexes: in 'RGBW', 'R' is on index 0, but we need to shift it left by 3 * 8bits,
# so in it's inverse, 'WBGR', it has exactly right index. Since micropython doesn't have [::-1] and recursive rev()
# isn't too efficient we simply do that by XORing (operator ^) each index with 3 (0b11) to make this flip.
# When dealing with just 'RGB' (3 letter string), this means same but reduced by 1 after XOR!.
# Example: in 'GRBW' we want final form of 0bGGRRBBWW, meaning G with index 0 needs to be shifted 3 * 8bit ->
# 'G' on index 0: 0b00 ^ 0b11 -> 0b11 (3), just as we wanted.
# Same hold for every other index (and - 1 at the end for 3 letter strings).

class Neopixel:
    def __init__(self, num_leds, state_machine, pin, mode="RGB", delay=0.0001):
        self.pixels = array.array("I", [0 for _ in range(num_leds)])
        self.mode = set(mode)   # set for better performance
        if 'W' in self.mode:
            # RGBW uses different PIO state machine configuration
            self.sm = rp2.StateMachine(state_machine, sk6812, freq=8000000, sideset_base=Pin(pin))
            # dictionary of values required to shift bit into position (check class desc.)
            self.shift = {'R': (mode.index('R') ^ 3) * 8, 'G': (mode.index('G') ^ 3) * 8,
                          'B': (mode.index('B') ^ 3) * 8, 'W': (mode.index('W') ^ 3) * 8}
        else:
            self.sm = rp2.StateMachine(state_machine, ws2812, freq=8000000, sideset_base=Pin(pin))
            self.shift = {'R': ((mode.index('R') ^ 3) - 1) * 8, 'G': ((mode.index('G') ^ 3) - 1) * 8,
                          'B': ((mode.index('B') ^ 3) - 1) * 8, 'W': 0}
        self.sm.active(1)
        self.num_leds = num_leds
        self.delay = delay
        self.brightnessvalue = 255

    # Set the overal value to adjust brightness when updating leds
    def brightness(self, brightness=None):
        if brightness == None:
            return self.brightnessvalue
        else:
            if brightness < 1:
                brightness = 1
        if brightness > 255:
            brightness = 255
        self.brightnessvalue = brightness

    # Create a gradient with two RGB colors between "pixel1" and "pixel2" (inclusive)
    # Function accepts two (r, g, b) / (r, g, b, w) tuples
    def set_pixel_line_gradient(self, pixel1, pixel2, left_rgb_w, right_rgb_w, how_bright = None):
        if pixel2 - pixel1 == 0:
            return
        right_pixel = max(pixel1, pixel2)
        left_pixel = min(pixel1, pixel2)

        for i in range(right_pixel - left_pixel + 1):
            fraction = i / (right_pixel - left_pixel)
            red = round((right_rgb_w[0] - left_rgb_w[0]) * fraction + left_rgb_w[0])
            green = round((right_rgb_w[1] - left_rgb_w[1]) * fraction + left_rgb_w[1])
            blue = round((right_rgb_w[2] - left_rgb_w[2]) * fraction + left_rgb_w[2])
            # if it's (r, g, b, w)
            if len(left_rgb_w) == 4 and 'W' in self.mode:
                white = round((right_rgb_w[3] - left_rgb_w[3]) * fraction + left_rgb_w[3])
                self.set_pixel(left_pixel + i, (red, green, blue, white), how_bright)
            else:
                self.set_pixel(left_pixel + i, (red, green, blue), how_bright)

    # Set an array of pixels starting from "pixel1" to "pixel2" (inclusive) to the desired color.
    # Function accepts (r, g, b) / (r, g, b, w) tuple
    def set_pixel_line(self, pixel1, pixel2, rgb_w, how_bright = None):
        for i in range(pixel1, pixel2 + 1):
            self.set_pixel(i, rgb_w, how_bright)

    # Set red, green and blue value of pixel on position <pixel_num>
    # Function accepts (r, g, b) / (r, g, b, w) tuple
    def set_pixel(self, pixel_num, rgb_w, how_bright = None):
        if how_bright == None:
            how_bright = self.brightness()
        pos = self.shift

        red = round(rgb_w[0] * (how_bright / 255))
        green = round(rgb_w[1] * (how_bright / 255))
        blue = round(rgb_w[2] * (how_bright / 255))
        white = 0
        # if it's (r, g, b, w)
        if len(rgb_w) == 4 and 'W' in self.mode:
            white = round(rgb_w[3] * (how_bright / 255))

        self.pixels[pixel_num] = white << pos['W'] | blue << pos['B'] | red << pos['R'] | green << pos['G']

    # Converts HSV color to rgb tuple and returns it
    # Function accepts integer values for <hue>, <saturation> and <value>
    # The logic is almost the same as in Adafruit NeoPixel library:
    # https://github.com/adafruit/Adafruit_NeoPixel so all the credits for that
    # go directly to them (license: https://github.com/adafruit/Adafruit_NeoPixel/blob/master/COPYING)
    def colorHSV(self, hue, sat, val):
        if hue >= 65536:
            hue %= 65536

        hue = (hue * 1530 + 32768) // 65536
        if hue < 510:
            b = 0
            if hue < 255:
                r = 255
                g = hue
            else:
                r = 510 - hue
                g = 255
        elif hue < 1020:
            r = 0
            if hue < 765:
                g = 255
                b = hue - 510
            else:
                g = 1020 - hue
                b = 255
        elif hue < 1530:
            g = 0
            if hue < 1275:
                r = hue - 1020
                b = 255
            else:
                r = 255
                b = 1530 - hue
        else:
            r = 255
            g = 0
            b = 0

        v1 = 1 + val
        s1 = 1 + sat
        s2 = 255 - sat

        r = ((((r * s1) >> 8) + s2) * v1) >> 8
        g = ((((g * s1) >> 8) + s2) * v1) >> 8
        b = ((((b * s1) >> 8) + s2) * v1) >> 8

        return r, g, b


    # Rotate <num_of_pixels> pixels to the left
    def rotate_left(self, num_of_pixels):
        if num_of_pixels == None:
            num_of_pixels = 1
        self.pixels = self.pixels[num_of_pixels:] + self.pixels[:num_of_pixels]

    # Rotate <num_of_pixels> pixels to the right
    def rotate_right(self, num_of_pixels):
        if num_of_pixels == None:
            num_of_pixels = 1
        num_of_pixels = -1 * num_of_pixels
        self.pixels = self.pixels[num_of_pixels:] + self.pixels[:num_of_pixels]

    # Update pixels
    def show(self):
        # If mode is RGB, we cut 8 bits of, otherwise we keep all 32
        cut = 8
        if 'W' in self.mode:
            cut = 0
        for i in range(self.num_leds):
            self.sm.put(self.pixels[i], cut)
        time.sleep(self.delay)

    # Set all pixels to given rgb values
    # Function accepts (r, g, b) / (r, g, b, w)
    def fill(self, rgb_w, how_bright = None):
        for i in range(self.num_leds):
            self.set_pixel(i, rgb_w, how_bright)
        time.sleep(self.delay)