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Potentiometer and the Microbit
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How to create pretty, colourful patterns on the microbit in python with neopixels. How to use hue and not just RGB colour space.
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jez
Pretty patterns with neopixels on python.
component examples
Neopixel Examples
2016-12-23 10:20:00 UTC

Examples of some pretty neopixel paterns on the microbit in Python.

See the component article on this website about Neopixels.

{:.ui .header .dividing}

Shifting Rainbow

Create a list of values that range in hue. Every 100 milliseconds, shift the list by 1 and update the neopixel display.

Python PXT.io

{% highlight python %} from microbit import * import neopixel

def shift_left(lst, n): """Shifts the lst over by n indices

>>> lst = [1, 2, 3, 4, 5]
>>> shift_left(lst, 2)
>>> lst
[3, 4, 5, 1, 2]
"""
assert (n > 0), "n should be non-negative integer"
def shift(ntimes):
    if ntimes == 0:
        return
    else:
        temp = lst[0]
        for index in range(len(lst) - 1):
            lst[index] = lst[index + 1]         
        lst[index + 1] = temp
        return shift(ntimes-1)
return shift(n)

def HSV_2_RGB(HSV): ''' Converts an integer HSV tuple (value range from 0 to 255) to an RGB tuple '''

# Unpack the HSV tuple for readability
H, S, V = HSV

# Check if the color is Grayscale
if S == 0:
    R = V
    G = V
    B = V
    return (R, G, B)

# Make hue 0-5
region = H // 43;

# Find remainder part, make it from 0-255
remainder = (H - (region * 43)) * 6;

# Calculate temp vars, doing integer multiplication
P = (V * (255 - S)) >> 8;
Q = (V * (255 - ((S * remainder) >> 8))) >> 8;
T = (V * (255 - ((S * (255 - remainder)) >> 8))) >> 8;

# Assign temp vars based on color cone region
if region == 0:
    R = V
    G = T
    B = P

elif region == 1:
    R = Q;
    G = V;
    B = P;

elif region == 2:
    R = P;
    G = V;
    B = T;

elif region == 3:
    R = P;
    G = Q;
    B = V;

elif region == 4:
    R = T;
    G = P;
    B = V;

else:
    R = V;
    G = P;
    B = Q;

return (R, G, B)

24 neopixels on pin0

np = neopixel.NeoPixel(pin0, 24)

each neopixel shifts in value by 24

hue_step = round(255 / len(np))

populate neopixel list with colours

for pixel in range(0, len(np)): hue = pixel * hue_step hsv = HSV_2_RGB((hue, 255,255)) np[pixel] = hsv print(np[pixel])

while True: shift_left(np, 1) np.show() sleep(100) {% endhighlight %}

Much nicer in PXT!

{% highlight javascript %} let neopixels = neopixel.create(DigitalPin.P0, 24, NeoPixelMode.RGB) neopixels.showRainbow(1, 360) basic.forever(() => { neopixels.rotate(1) // shift array neopixels.show() basic.pause(100) }) {% endhighlight %}