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;
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 â€¦