Reference code for driving the microbit neopixel library through a rainbow effect

neopixel_microbit.py

from microbit import *
import neopixel

# Setup the Neopixel strip on pin0 with a length of 8 pixels
np = neopixel.NeoPixel(pin0, 8)

def wheel(wheelByte):
    wheelByte = 255 - wheelByte
    if wheelByte < 85:
        return (255 - wheelByte * 3, 0, wheelByte * 3)
    if wheelByte < 170:
        wheelByte = wheelByte - 85
        return (0, wheelByte * 3, 255 - wheelByte * 3)
    wheelByte = wheelByte - 170
    return (wheelByte * 3, 255 - wheelByte * 3, 0)

wheelPos = 0

while True:
    #Iterate over each LED in the strip
    for pixel_id in range(0, len(np)):

        # Assign the current LED a color value from the rainbow sequence, with current offset
        np[pixel_id] =wheel((wheelPos + pixel_id) % 255)

    # Display the current pixel data on the Neopixel strip
    np.show()

    wheelPos = (wheelPos + 1) % 255

    sleep(100)

sleep(100) is a mistake, as that's in seconds (by contrast with sleep_ms(100))