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neopixels.md

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Use Neopixels with the Microbit & Python
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The micropython library enables the microbit to drive a Neopixel module. Here's how to set it up.
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jez
Use the neopixel library to light an array of neopixels
external
Neopixels
Video & teaser image by Adafruit (CC-BY-2.0)
2016-12-23 10:20:00 UTC
2016-12-23 10:20:00 UTC

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Neopixels are RGB LEDs sold by an electronics company called Adafruit. The modules come in different shapes and can contain any number of RGB LEDs. Each LED can be controlled (or addressed) individually. The microbit can drive around 8 LEDs; to control modules with more LEDs you'll need to use an external 5v power source.

You can get generic, Neopixel-style modules by searching for 'ws2812 LED' on eBay or Amazon.

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Components

Most neopixel modules require the user to solder on their own connections. This is simple; here's one of my modules:

My soldered neopixel{:.ui .image}

  • Solder wires to PWR, GND and IN.
  • In this example the wires are colour-coded: black (for GND), red (for PWR) or yellow (for IN)

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Electronics

Wiring up a Neopixel Module for the microbit{:.ui .image}

Connect the pins to the microbit. In this example, the in pin on the neopixel is connected to pin 0.

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Code

Neopixels can now be used in PXT. I'll update this page.

Python

The neopixel library must be imported:

{% highlight python %} import neopixel {% endhighlight %}

Initialise the neopixel module. Here the variable neopixels is assigned to neopixel.NeoPixel(pin0, 12).

{% highlight python %}

neopixel connected to pin0 and there are 12 LEDs

neopixels = neopixel.NeoPixel(pin0, 12) {% endhighlight %}

Each neopixel is now in the list neopixels and can be individually addressed. Colour is controlled by a tuple of RGB values:

{% highlight python %} neopixels[0] = (0,255,0) # First LED to red neopixels[1] = (255,150,0) # Second LED to white neopixels[-1] = (255,0,0) # Final LED to yellow

Neopixels only change when 'show' method is called

neopixels.show () {% endhighlight %}

Simple Traffic Light (as above)

Light three pixels next to each other either red, amber or red.

{% highlight python %}

from microbit import * import neopixel

neopixels = neopixel.NeoPixel(pin0, 12)

neopixels[0] = (255,150,0) # First LED to Amber neopixels[1] = (0,255,0) # Second LED to Green neopixels[-1] = (255,0,0) # Final LED to Red

neopixels.show() # Light the LEDs {% endhighlight %}

Sequentially Light Each Pixel

Light one LED in the neopixel red for 200 milliseconds then light the next one.

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

neopixels = neopixel.NeoPixel(pin0, 12)

while True: # Do this for each pixel in the neopixels list for pixel in range(0, len(neopixels)): neopixels[pixel] = (255,0,0) # Turn on red neopixels.show() # show red sleep(200)
neopixels[pixel] = (0,0,0) # Turn off red {% endhighlight %}

Experiment

  • Use random.ranrange(0,255) to set an LED to a random colour
  • Define a function to fade in the LED