[MicroPython]TPYBoard v102炫彩跑马灯WS2812B

一、实验目的

了解ws2812b的工作原理
学习ws2812b的驱动方法

二、实验器材

TPYBoard v102 1块
ws2812b RGB-Ring-8 1个
micro USB数据线 1条
杜邦线若干

三、WS2812B的介绍

WS2812B是一个集控制电路与发光电路于一体的智能外控LED光源。其外型与一个5050LED灯珠相同，每个元件即为一个像素点。像素点内部包含了智能数字接口数据锁存信号整形放大驱动电路，还包含有高精度的内部振荡器和可编程定电流控制部分，有效保证了像素点光的颜色高度一致。

数据协议采用单线归零码的通讯方式，像素点在上电复位以后， DIN端接受从控制器传输过来的数据，首先送过来的24bit数据被第一个像素点提取后，送到像素点内部的数据锁存器，剩余的数据经过内部整形处理电路整形放大后通过DO端口开始转发输出给下一个级联的像素点，每经过一个像素点的传输，信号减少24bit。像素点采用自动整形转发技术，使得该像素点的级联个数不受信号传送的限制，仅仅受限信号传输速度要求。

实物图

上图是8个灯珠的。
WS2812B的引脚说明：

硬件连接
将TPYBoard v102与WS2812B的接线示意图，如下：

程序源码如下：

import   pyb
import   math
   
from   ws2812 import WS2812
   
   
ring   = WS2812(spi_bus=1, 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)
    pyb.delay(100)

里面还需要引入一个ws2812.py 文件。内容如下：

import   gc
import   pyb
  
  
class   WS2812:
    """
    Driver for WS2812 RGB LEDs. May be used   for controlling single LED or chain
    of LEDs.
  
    Example of use:
  
        chain = WS2812(spi_bus=1,   led_count=4)
        data = [
            (255, 0, 0),    # red
            (0, 255, 0),    # green
            (0, 0, 255),    # blue
            (85, 85, 85),   # white
        ]
        chain.show(data)
  
    Version: 1.0
    """
    buf_bytes = (0x11, 0x13, 0x31, 0x33)
  
    def __init__(self, spi_bus=1,   led_count=1, intensity=1):
        """
        Params:
        * spi_bus = SPI bus ID (1 or 2)
        * led_count = count of LEDs
        * intensity = light intensity (float   up to 1)
        """
        self.led_count = led_count
        self.intensity = intensity
  
        # prepare SPI data buffer (4 bytes   for each color)
        self.buf_length = self.led_count * 3   * 4
        self.buf = bytearray(self.buf_length)
  
        # SPI init
        self.spi = pyb.SPI(spi_bus,   pyb.SPI.MASTER, baudrate=3200000, polarity=0, phase=1)
  
        # turn LEDs off
        self.show([])
  
    def show(self, data):
        """
        Show RGB data on LEDs. Expected data   = [(R, G, B), ...] where R, G and B
        are intensities of colors in range   from 0 to 255. One RGB tuple for each
        LED. Count of tuples may be less than   count of connected LEDs.
        """
        self.fill_buf(data)
        self.send_buf()
  
    def send_buf(self):
        """
        Send buffer over SPI.
        """
        self.spi.send(self.buf)
        gc.collect()
  
    def update_buf(self, data, start=0):
        """
        Fill a part of the buffer with RGB   data.
  
        Order of colors in buffer is changed   from RGB to GRB because WS2812 LED
        has GRB order of colors. Each color   is represented by 4 bytes in buffer
        (1 byte for each 2 bits).
  
        Returns the index of the first unfilled   LED
  
        Note: If you find this function ugly,   it's because speed optimisations
        beated purity of code.
        """
  
        buf = self.buf
        buf_bytes = self.buf_bytes
        intensity = self.intensity
  
        mask = 0x03
        index = start * 12
        for red, green, blue in data:
            red = int(red * intensity)
            green = int(green * intensity)
            blue = int(blue * intensity)
  
            buf[index] = buf_bytes[green   >> 6 & mask]
            buf[index+1] = buf_bytes[green   >> 4 & mask]
            buf[index+2] = buf_bytes[green   >> 2 & mask]
            buf[index+3] = buf_bytes[green   & mask]
  
            buf[index+4] = buf_bytes[red   >> 6 & mask]
            buf[index+5] = buf_bytes[red   >> 4 & mask]
            buf[index+6] = buf_bytes[red   >> 2 & mask]
            buf[index+7] = buf_bytes[red   & mask]
  
            buf[index+8] = buf_bytes[blue   >> 6 & mask]
            buf[index+9] = buf_bytes[blue   >> 4 & mask]
            buf[index+10] = buf_bytes[blue   >> 2 & mask]
            buf[index+11] = buf_bytes[blue   & mask]
  
            index += 12
  
        return index // 12
  
    def fill_buf(self, data):
        """
        Fill buffer with RGB data.
  
        All LEDs after the data are turned   off.
        """
        end = self.update_buf(data)
  
        # turn off the rest of the LEDs
        buf = self.buf
        off = self.buf_bytes[0]
        for index in range(end * 12,   self.buf_length):
            buf[index] = off
            index += 1