12. 控制 APA102 LED

APA102 LED，也称为 DotStar LED，是可单独寻址的全彩 RGB LED，通常呈串状。它们与 NeoPixels 的不同之处在于它们需要两个引脚来控制——时钟和数据引脚。它们可以在比 NeoPixels 更高的数据和 PWM 频率下运行，并且更适合视觉暂留效果。

要创建 APA102 对象，请执行以下操作：

>>> import machine, apa102
>>> strip = apa102.APA102(machine.Pin(5), machine.Pin(4), 60)

这将配置一个 60 像素的 APA102 条带，其时钟位于 GPIO5 上，数据位于 GPIO4 上。您可以调整引脚数和像素数以满足您的需要。

RGB 颜色数据以及亮度级别按特定顺序发送到 APA102。通常这是. 如果您使用的是较新的 APA102C LED 之一，则绿色和蓝色会交换，因此顺序为。APA102 有更多的方形镜头，而 APA102C 有更多的圆形镜头。如果您使用的是 APA102C 条带并且更喜欢以 RGB 顺序而不是 RBG 提供颜色，您可以像这样自定义元组颜色顺序：(Red, Green, Blue, Brightness) (Red, Blue, Green, Brightness)

>>> strip.ORDER = (0, 2, 1, 3)

要设置像素的颜色，请使用：

>>> strip[0] = (255, 255, 255, 31) # set to white, full brightness
>>> strip[1] = (255, 0, 0, 31) # set to red, full brightness
>>> strip[2] = (0, 255, 0, 15) # set to green, half brightness
>>> strip[3] = (0, 0, 255, 7)  # set to blue, quarter brightness

使用该write()方法将颜色输出到 LED：

>>> strip.write()

示范：

import time
import machine, apa102

# 1M strip with 60 LEDs
strip = apa102.APA102(machine.Pin(5), machine.Pin(4), 60)

brightness = 1  # 0 is off, 1 is dim, 31 is max

# Helper for converting 0-255 offset to a colour tuple
def wheel(offset, brightness):
    # The colours are a transition r - g - b - back to r
    offset = 255 - offset
    if offset < 85:
        return (255 - offset * 3, 0, offset * 3, brightness)
    if offset < 170:
        offset -= 85
        return (0, offset * 3, 255 - offset * 3, brightness)
    offset -= 170
    return (offset * 3, 255 - offset * 3, 0, brightness)

# Demo 1: RGB RGB RGB
red = 0xff0000
green = red >> 8
blue = red >> 16
for i in range(strip.n):
    colour = red >> (i % 3) * 8
    strip[i] = ((colour & red) >> 16, (colour & green) >> 8, (colour & blue), brightness)
strip.write()

# Demo 2: Show all colours of the rainbow
for i in range(strip.n):
    strip[i] = wheel((i * 256 // strip.n) % 255, brightness)
strip.write()

# Demo 3: Fade all pixels together through rainbow colours, offset each pixel
for r in range(5):
    for n in range(256):
        for i in range(strip.n):
            strip[i] = wheel(((i * 256 // strip.n) + n) & 255, brightness)
        strip.write()
    time.sleep_ms(25)

# Demo 4: Same colour, different brightness levels
for b in range(31,-1,-1):
    strip[0] = (255, 153, 0, b)
    strip.write()
    time.sleep_ms(250)

# End: Turn off all the LEDs
strip.fill((0, 0, 0, 0))
strip.write()