LEDs

The examples below assume a device, such as a buggy, has 4 RGB LEDs (WS2812) on pin8.
The neopixel module is used to drive these RGB LEDs.
In RGB, R stands for red, G stands for green, and B stands for blue.
Each RGB LED can produce a full spectrum of colors independent to all of the other RGB LEDs.
Each ZIP LED has a Red, Green and Blue element within the LED, and each of these can have brightness set from 0 to 255.

NeoPixel module

The neopixel module allows use of multiple RGB LEDs connected to one pin so that each can have their own color and brightness set.

First, import the neopixel library with import neopixel.

from microbit import *
import neopixel

Set up LEDs

neopixel.NeoPixel(pin, n): Initialise a strip of RGB LEDs

pin is the pin that they are connected by.

n is the number of LEDs

The code below sets up 4 LEDs connected to pin8 via: np = neopixel.NeoPixel(pin8, 4).

The variable, np, is the neopixel object that is used to control the LEDs.

from microbit import *
import neopixel


np = neopixel.NeoPixel(pin8, 4)

Set LED color and brightness

np[n] = (red, green, blue): Set the red, green and blue brightness from 0 to 255 for a RGB LED at position n.

Each LED is set by indexing it (like with a Python list, starting from 0).
e.g the LED in position 0 is np[0].
Neopixels are given RGB (red, green, blue) values between 0-255 as a tuple.
A value of 0 is off, while 255 is full brightness.
When red, green and blue are all full brightness, (255, 255, 255), the color is white.

The code below sets the RGB values to (255, 255, 255) for the LED in position 0.

from microbit import *
import neopixel


np = neopixel.NeoPixel(pin8, 4)
np[0] = (255, 255, 255)

The code below sets the colors of the 4 LEDs: np[0] is white, np[1] is red, np[2] is green and np[3] is blue, with all at full brightness.

from microbit import *
import neopixel


np = neopixel.NeoPixel(pin8, 4)
np[0] = (255, 255, 255)
np[1] = (255, 0, 0)
np[2] = (0, 255, 0)
np[3] = (0, 0, 255)

Tasks

For quick RGB values for common colors, see https://www.rapidtables.com/web/color/RGB_Color.html

Write code to set the last LEDS at position 1, 2 and 3 to yellow, cyan and magenta.

Show LEDs

Setting the colors for LEDs doesn’t change the displayed color of the LEDs until show() is used on the neopixel object that was set up. e.g. np.show()

show(): Show the LEDs using their color settings. This must be called for any updates to the LEDs to become visible.

The code below displays the set colors for the neopixel LEDS using np.show()

from microbit import *
import neopixel


np = neopixel.NeoPixel(pin8, 4)
np[0] = (255, 255, 255)
np.show()

Clear LEDs

clear(): Clear all the LEDs so that they have no colors set and turns off the LEDs.

The code below uses the variable buggy_lights for the neopixel settings.
The front lights are at position 0 and 1. They are set to dull blue.
The rear lights are at position 2 and 3. They are set to dull red.
The lights are turned on for 2 seconds then turned off using clear().

from microbit import *
import neopixel


buggyLights = NeoPixel(pin8, 4)
dull_blue = [20, 20, 25]
dull_red = [25, 0, 0]
buggyLights[0] = dull_blue
buggyLights[1] = dull_blue
buggyLights[2] = dull_red
buggyLights[3] = dull_red
buggyLights.show()
sleep(2000)
buggyLights.clear()

Tasks

For quick RGB values for common colors, see https://www.rapidtables.com/web/color/RGB_Color.html

Modify the colors used in the code by changing the variable names and their values. | Use yellow and purple instead of red and blue.

LED values

To read the color of a specific pixel just reference it.

np[n](): Return the red, green and blue value for the RGB LED at position n.

The code below sets the LED to a sandy brown color. The for loop displays each value in the tuple (255, 0, 0).

from microbit import *
import neopixel


buggy_lights = neopixel.NeoPixel(pin8, 4)
buggy_lights[0] = (255, 0, 0)
for i in buggy_lights[0]:
    display.scroll(i)

color lists

A list of colors can be used to create a colorful display.
2 for-loops are used, one nested inside the other.
for c in color_list: loops through the colors.
for i in range(4): loops through each LED to set the color for it.

from microbit import *
import neopixel


white = (255, 255, 255)
red = (255, 0, 0)
yellow = (255, 255, 0)
green = (0, 128, 0)
cyan = (0, 255, 255)
blue = (0, 0, 255)
magenta = (255, 0, 255)

color_list = [white, red, yellow, green, cyan, blue, magenta, ]

buggy_lights = neopixel.NeoPixel(pin8, 4)
for c in color_list:
    for i in range(4):
        buggy_lights[i]=c
    buggy_lights.show()
    sleep(200)

Tasks

See https://www.indezine.com/products/powerpoint/learn/color/color-rgb.html

Modify the code to use a shorter list of colors, with just the primary colors.
Modify the code to use a shorter list of colors, with just the secondary colors.

Random brightness

Repeatedly displays random colors onto the LED strip.

This example requires a strip of 4 Neopixels (WS2812) connected to pin8.

from microbit import *
import neopixel
from random import randint

# Setup the Neopixel strip on pin8 with a length of 4 pixels
np = neopixel.NeoPixel(pin8, 48)

while True:
    #Iterate over each LED in the strip

    for pixel_id in range(0, len(np)):
        red = randint(0, 60)
        green = randint(0, 60)
        blue = randint(0, 60)

        # Assign the current LED a random red, green and blue value between 0 and 60
        np[pixel_id] = (red, green, blue)

        # Display the current pixel data on the Neopixel strip
        np.show()
        sleep(100)

Repeatedly display random colors on the 4 LEDs connected to pin8.

from microbit import *
import neopixel
import random


# Setup the Neopixel strip on pin8 with a length of 4 pixels
NUM_PIXELS = 4
LED_PIN = pin8
np = neopixel.NeoPixel(LED_PIN, NUM_PIXELS)

def front_lights():
    # LED 0 and 1; red, green and blue value between 0 and 255
    np[0] = (0, 255, 0)
    np[1] = (0, 255, 0)
    # Display the current pixel data on the Neopixel strip
    np.show()

def rear_lights():
    # LED 2 and 3; red, green and blue value between 0 and 255
    np[2] = (255, 0, 0)
    np[3] = (255, 0, 0)
    # Display the current pixel data on the Neopixel strip
    np.show()

def same_random_pixels():
    # Iterate over each LED in the strip
    red = random.randint(0, 255)
    green = random.randint(0, 255)
    blue = random.randint(0, 255)
    for pixel_id in range(NUM_PIXELS):
        # Assign the current LED a random red, green and blue value between 0 and 60
        np[pixel_id] = (red, green, blue)
    # Display the current pixel data on the Neopixel strip
    np.show()


front_lights()
rear_lights()

while True:
    sleep(400)
    same_random_pixels()