The BitBot comes with a set of 12 programmable NeoPixel LEDs built along the arms of the robot - 6 each side. Each one is individually addressable (0 .. 11) and programmable using standard RGB values.

NeoPixels

Importing the neopixel library is a required step because it doesn't come in with the traditional blank microbit star import. Then we can set colour using an rgb tuple.

from microbit import *
import neopixel

pixels = neopixel.NeoPixel(pin13, 12)

pixels[0] = (255, 255, 255)
pixels.show()

We can set all pixels to the same colour easily too.

colour = (125, 10, 22)

for i in range(0, len(pixels)):
    pixels[i] = colour

pixels.show()

All changes to the pixel values have to be followed up with a call to show(). Pixel values also persist between calls to show() so that turning off all LEDs is a good practice before changing which LEDs are shown.

# turn off all LEDs

for i in range(0, len(pixels)):
    pixels[i] = (0, 0, 0)

pixels.show()

Microbit LEDs

We can add this NeoPixel functionality to the BitBot vehicle so that we can have headlights, reverse lights, brake lights...

# import neopixel

class MicrobitLEDs:

    def __init__(self, led_pin):
        self.neopixels = neopixel.NeoPixel(led_pin, 12)

    def all(self, pixels, colour):
        for i in pixels:
            self.neopixels[i] = colour
        self.neopixels.show()

    def clear(self):
        self.all(range(0, 12), (0, 0, 0))

    def headlights(self, colour = (255, 255, 255)):
        self.clear()
        self.all([5, 11], colour)

    def reversing_lights(self, colour = (127, 127, 127)):
        self.clear()
        self.all([0, 6], colour)

    def brake_lights(self, colour = (127, 0, 0)):
        self.clear()
        self.all([0, 6], colour)

    def left_lights(self, colour):
        self.clear()
        self.all(range(0, 6), colour)

    def right_lights(self, colour):
        self.clear()
        self.all(range(6, 12), colour)

    def sweep_forward(self, colour, delay = 25):

        for i in range(0, 6):
            self.clear()
            self.neopixels[i] = colour
            self.neopixels[i + 6] = colour
            self.neopixels.show()
            sleep(delay)

    def sweep_backward(self, colour, delay = 25):

        for i in range(11, 5, -1):
            self.clear()
            self.neopixels[i] = colour
            self.neopixels[i - 6] = colour
            self.neopixels.show()
            sleep(delay)

I also added functions to light the left and right arms of the vehicle independently and two cool effects - swiping a colour from the back LEDs all the way to the front one (and the reverse effect) just to show off.

BitBot

We can add this code into the [BitBot class]({ FIX % link _posts/2019-05-16-microbit-motoring.md %}) like this:

class BitBot:

    def __init__(self):
        # ...other config here...
        self.leds = MicrobitLEDs(pin13)

    def forward(self, percent = 25):
        self.leds.headlights()
        # ...motor control...

    def reverse (self, percent = 25):
        self.leds.reversing_lights()
        # ...motor control...
        

    def stop(self):
        self.leds.brake_lights()
        # ...motor control...

Rainbows

For reference, since the LEDs are all RGB programmable, we can set each one to a different colour of the rainbow.