CircuitPython NeoPixel

NeoPixels are a revolutionary and ultra-popular way to add lights and color to your project. These stranded RGB lights have the controller inside the LED, so you just push the RGB data and the LEDs do all the work for you! They're a perfect match for CircuitPython

You can drive 300 pixels with brightness control and 1000 pixels without (set brightness=1.0 in object creation). That's because to adjust the brighness we have to dynamically re-create the datastream each write.

Here's an example with a lot of different visual effects you can check out. You'll need the neopixel.mpy library file if you don't have it yet!

# CircuitPython demo - NeoPixel

import board
import neopixel
import time

pixpin = board.D1
numpix = 10

strip = neopixel.NeoPixel(pixpin, numpix, brightness=0.3, auto_write=False)

def wheel(pos):
    # Input a value 0 to 255 to get a color value.
    # The colours are a transition r - g - b - back to r.
    if (pos < 0) or (pos > 255):
        return (0, 0, 0)
    if (pos < 85):
        return (int(pos * 3), int(255 - (pos*3)), 0)
    elif (pos < 170):
        pos -= 85
        return (int(255 - pos*3), 0, int(pos*3))
        pos -= 170
        return (0, int(pos*3), int(255 - pos*3))

def rainbow_cycle(wait):
    for j in range(255):
        for i in range(len(strip)):
            idx = int ((i * 256 / len(strip)) + j)
            strip[i] = wheel(idx & 255)

while True:
    strip.fill((255, 0, 0))

    strip.fill((0, 255, 0))

    strip.fill((0, 0, 255))

    rainbow_cycle(0.001)    # rainbowcycle with 1ms delay per step

This code will work with any NeoPixel-compatible.

NeoPixels can be driven by any pin.

For powering the pixels from the board, the 3.3V regulator output from the Trinket/Gemma M0 can handle about 500mA peak which is about 50 pixels with 'average' use. If you want really bright lights and a lot of pixels, we recommend powering direct from the power source. On the Gemma M0 this is the Vout pad - that pad has direct power from USB or BAT, depending on which is higher voltage. On the Trinket M0 the USB or BAT pins will give you direct power from the USB port or battery.

The NeoPixel object's argument list requires the pin you'll use (any pin can be used) and the number of pixels. There's two optional arguments, brightness (range from 0 off to 1.0 full brightness) and auto_write. When auto_write default is set to True, every change is immediately written to the strip of pixels, this is easier to use but way slower. if you set auto_write=False then you will  have to call when you want to actually write color data out.

You can easily set colors by indexing into the location strip[n] = (red, green, blue). For example, strip[0] = (100, 0, 0) will set the first pixel to a medium-brightness red, and strip[2] = (0, 255, 0) will set the third pixel to bright green. Then, if you have auto_write=Falsedon't forget to call 

Verify the wiring on your strip or device - plugging into the 'DOUT' side is a common mistake! Wire up NeoPixels only while the Trinket or Gemma is not on, to avoid possible damage!

If the power to the NeoPixels is > 5.5V you may have some difficulty driving some strips, in which case you may need to lower the voltage to 4.5-5V or use a level shifter

We have a ton more information on general purpose NeoPixel know-how at our NeoPixel UberGuide
Last updated on 2018-03-16 at 06.24.08 PM Published on 2017-07-26 at 06.08.30 PM