Tag: neopixel

Cheap NeoPixels at the Dollar Store

Exhibit A:

box of "Monster BASICS" Sound reactive RGB+IC Color Flow LED strip

also known as “Monster BASICS Sound reactive RGB+IC Color Flow LED strip”. It’s $5 or so at Dollarama, and includes a USB cable for power and a remote control. It’s two metres long and includes 60 RGB LEDs. Are these really super-cheap NeoPixel clones?

I’m going to keep the USB power so I can power it from a power bank, but otherwise convert it to a string of smart LEDs. We lose the remote control capability.

Pull back the heatshrink at the USB end:

led strip with shrink tubing pulled back to show the +5 V, Din and GND solder tterminals

… and there are our connectors. We want to disconnect the blue Din (Data In) line from the built in controller, and solder new wires to Din and GND to run from a microcontroller board.

led strip with additional wires soldered to Din and GND contacts

Maybe not the best solder job, but there are new wires feeding through the heatshrink and soldered onto the strip.

led strip with two additional wires soldered in and heatshrink pushed back, all held in place by a cable tie

Here’s the heatshrink pushed back, and everything secured with a cable tie.

Now to feed it from standard MicroPython NeoPixel code, suitably jazzed up for 60 pixels.

a glowing multicolour reel of of LEDs

A pretty decent result for $5!

WeAct F411 + MicroPython + NeoPixels

Further to the Canaduino STM32 boards with MicroPython writeup, I thought I’d start showing how you’d interface common electronics to the WeAct F411 boards. First off, NeoPixels!

Rather than use the Adafruit trade name, these are more properly called WS2812 LEDs. Each one contains a tiny microcontroller and it only takes three connections to drive a long chain of addressable colour LEDs. The downside is that the protocol to drive these is a bit of a bear, and really needs an accurate, fast clock signal to be reliable.

The STM32F411 chip does have just such a clock, and the generic micropython-ws2812 library slightly misuses the SPI bus to handle the signalling. The wiring’s simple:

  • F411 GND to WS2812 GND;
  • F411 3V3 to WS2812 5V;
  • F411 PA7 (SPI1_MOSI) PB15 (SPI2_MOSI) to WS2812 DIn

Next, copy ws2812.py into the WeAct F411’s flash. Now create a script to drive the LEDs. Here’s one to drive 8 LEDs, modified from the library’s advanced example:

# -*- coding: utf-8 -*-

import time
import math

from ws2812 import WS2812

ring = WS2812(spi_bus=2, led_count=8, intensity=0.1)

def data_generator(led_count):
    data = [(0, 0, 0) for i in range(led_count)]
    step = 0
    while True:
        red = int((1 + math.sin(step * 0.1324)) * 127)
        green = int((1 + math.sin(step * 0.1654)) * 127)
        blue = int((1 + math.sin(step * 0.1)) * 127)
        data[step % led_count] = (red, green, blue)
        yield data
        step += 1

for data in data_generator(ring.led_count):
    ring.show(data)
    time.sleep_ms(100)

Previously I said you’d see your WS2812s flicker and shimmer from the SPI bus noise. I thought it was cool, but I suspect it was also why the external flash on my F411 board just died. By pumping data into PA7, I was also hammering the flash chip’s DI line …