1. 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 colours 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.

1.1. NeoPixel module

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

First, import the neopixel library with import neopixel.

from microbit import *
import neopixel

1.2. 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: lights = neopixel.NeoPixel(pin8, 4).

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

from microbit import *
import neopixel


lights = neopixel.NeoPixel(pin8, 4)

1.3. Set LED colour and brightness

lights[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 lights[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 colour is white.

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

from microbit import *
import neopixel


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

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

from microbit import *
import neopixel


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

Tasks

For quick RGB values for common colours, 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.

1.4. Show LEDs

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

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

The code below displays the set colours for the neopixel LEDS using lights.show()

from microbit import *
import neopixel


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

1.5. Clear LEDs

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

The code below uses the variable 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


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

Tasks

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

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

1.6. LED values

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

lights[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 colour.

The for loop displays each value in the tuple (255, 0, 0).

from microbit import *
import neopixel


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