ws2812燈帶python案例 · 樹莓派gpiozero庫

# 硬件器材 * 樹莓派3B+ * [古德微樹莓派擴展板]([https://item.taobao.com/item.htm?spm=a1z10.3-c.w4002-22298106374.9.158170c90MOfva&id=578376338324](https://item.taobao.com/item.htm?spm=a1z10.3-c.w4002-22298106374.9.158170c90MOfva&id=578376338324)) * [柔性ws2812貼片led燈帶]([https://item.taobao.com/item.htm?spm=a1z10.3-c.w4002-22298106374.9.4cbc70c9a29bu7&id=584515172003](https://item.taobao.com/item.htm?spm=a1z10.3-c.w4002-22298106374.9.4cbc70c9a29bu7&id=584515172003)) 鏈接方式如下圖。 ![](https://img.kancloud.cn/28/48/28481d4419647c9bbcdf12263c5e8dc5_1920x886.png) >當然采用古德微擴展板只是為了方便，直接插到板子上就好了，其實只要有樹莓派和燈帶，燈帶正確的連接到樹莓派就可以使用本教程。 # 安裝燈帶相關的python庫樹莓派控制led燈帶需要用到[rpi-ws281x-python](https://github.com/rpi-ws281x/rpi-ws281x-python)庫，具體安裝方法如下。 ``` sudo pip install rpi-ws281x ``` # 用法簡介控制燈帶主要用的是`PixelStrip`類，這個類的方法和屬性如下： ``` >>> dir(rpi_ws281x.PixelStrip) [..., 'begin', 'getBrightness', 'getPixelColor', 'getPixelColorRGB', 'getPixels', 'numPixels', 'setBrightness', 'setGamma', 'setPixelColor', 'setPixelColorRGB', 'show'] ``` ## 初始化燈帶初始化燈帶主要用到如下代碼： ``` strip = PixelStrip(LED_COUNT, LED_PIN, LED_FREQ_HZ, LED_DMA, LED_INVERT, LED_BRIGHTNESS, LED_CHANNEL) ``` 參數中大寫的變量是在測試代碼中定義了的，含義如下： ```python # LED 配置: LED_COUNT = 10 # 要控制LED的數量. LED_PIN = 18 # GPIO接口 (PWM編碼). LED_BRIGHTNESS = 255 # 設置LED亮度 (0-255) #以下LED配置無需修改 LED_FREQ_HZ = 800000 # LED信號頻率（以赫茲為單位）（通常為800khz） LED_DMA = 10 # 用于生成信號的DMA通道（嘗試10） LED_INVERT = False # 反轉信號（使用NPN晶體管電平移位時） ``` 所以你會看到古德微的平臺中只需要你設定燈帶LED燈的數量，引腳和亮度了。 ![](https://img.kancloud.cn/25/6e/256ed9f1d08cf1588c589107b7a9ee74_603x92.png) 圖片中的這個積木塊與`strip = PixelStrip(18 10, 800000, 10, False, 50, 0)`是完全等效的。其中**LED信號頻率、DMA通道（不明白沒關系）、翻轉信號以及信道等參數無需配置**，所以這個庫其實還可以繼續簡化的。 ## 顏色設置 `rip_ws281x`庫中顏色的設置是通過`Color`類實現的，等效于下列積木塊： ![](https://img.kancloud.cn/9f/99/9f9950162f07565be96d37e6ecfeba9e_252x134.png) 幫助信息如下： ``` Color(red, green, blue, white=0) 根據參數指定的紅綠藍顏色的值合成24位的顏色.。每種顏色的范圍是0到255，最小值是0，最大值255。 ``` 所以上面積木塊等效的代碼就是`Color(50, 30, 10)`。 ## 設定LED顏色 ![](https://img.kancloud.cn/0e/82/0e8222a743769767e893593cd10fc6b5_522x134.png) 設定顏色是通過`setPixelColor()`方法實現的，上述積木塊的等效代碼是`strip.setPixelColor(1, Color(50, 30, 10))` ## 其他 ![](https://img.kancloud.cn/9b/df/9bdfe7c9f2302aa3acefcd370ed67ac9_767x387.png) 實際上每種積木塊都有對應的方法，而且代碼相比來說更加靈活，比如設定顏色： ``` setPixelColorRGB(self, n, red, green, blue, white=0) unbound rpi_ws281x.rpi_ws281x.PixelStrip method Set LED at position n to the provided red, green, and blue color. Each color component should be a value from 0 to 255 (where 0 is the lowest intensity and 255 is the highest intensity). ``` 直接通過顏色指定單個LED燈的顏色，比如`setPixelColorRGB(1, 50, 30, 10)`，也可以根據自己的使用習慣定義自己的函數。同時`'getBrightness', 'getPixelColor', 'getPixelColorRGB', 'getPixels', 'numPixels'`等用來獲取燈帶信息的函數，是積木塊有待實現的。 # 燈帶特效 ## 顏色刷新 ![](https://img.kancloud.cn/18/ea/18eab2e24339d6435c1c1204d946a73e_482x206.png) 開始的時候燈帶沒有顏色，一共60個LED燈，從0開始，每隔0.05秒，點亮一共LED燈，這樣整個燈帶就從不亮，到全亮，顏色可以指定，比如原來是全綠色，就可以用紅色依次替代原來的綠色。 ![](https://img.kancloud.cn/5c/07/5c0734e9593e98587beb2225c8895368_1407x751.png) # 測試案例代碼測試案例提供了多種特效，代碼也寫的很有參考價值。復制下面的代碼，并保存為strandtest.py，按照圖中的命令執行就可以了。 ![](https://img.kancloud.cn/26/b1/26b11f0f1e58fe1b292799c4e031f2d9_595x178.png) ``` #!/usr/bin/env python3 # NeoPixel library strandtest example # Author: Tony DiCola (tony@tonydicola.com) # # Direct port of the Arduino NeoPixel library strandtest example. Showcases # various animations on a strip of NeoPixels. import time from rpi_ws281x import PixelStrip, Color import argparse # LED strip configuration: LED_COUNT = 16 # Number of LED pixels. LED_PIN = 18 # GPIO pin connected to the pixels (18 uses PWM!). # LED_PIN = 10 # GPIO pin connected to the pixels (10 uses SPI /dev/spidev0.0). LED_FREQ_HZ = 800000 # LED signal frequency in hertz (usually 800khz) LED_DMA = 10 # DMA channel to use for generating signal (try 10) LED_BRIGHTNESS = 255 # Set to 0 for darkest and 255 for brightest LED_INVERT = False # True to invert the signal (when using NPN transistor level shift) LED_CHANNEL = 0 # set to '1' for GPIOs 13, 19, 41, 45 or 53 # Define functions which animate LEDs in various ways. def colorWipe(strip, color, wait_ms=50): """Wipe color across display a pixel at a time.""" for i in range(strip.numPixels()): strip.setPixelColor(i, color) strip.show() time.sleep(wait_ms / 1000.0) def theaterChase(strip, color, wait_ms=50, iterations=10): """Movie theater light style chaser animation.""" for j in range(iterations): for q in range(3): for i in range(0, strip.numPixels(), 3): strip.setPixelColor(i + q, color) strip.show() time.sleep(wait_ms / 1000.0) for i in range(0, strip.numPixels(), 3): strip.setPixelColor(i + q, 0) def wheel(pos): """Generate rainbow colors across 0-255 positions.""" if pos < 85: return Color(pos * 3, 255 - pos * 3, 0) elif pos < 170: pos -= 85 return Color(255 - pos * 3, 0, pos * 3) else: pos -= 170 return Color(0, pos * 3, 255 - pos * 3) def rainbow(strip, wait_ms=20, iterations=1): """Draw rainbow that fades across all pixels at once.""" for j in range(256 * iterations): for i in range(strip.numPixels()): strip.setPixelColor(i, wheel((i + j) & 255)) strip.show() time.sleep(wait_ms / 1000.0) def rainbowCycle(strip, wait_ms=20, iterations=5): """Draw rainbow that uniformly distributes itself across all pixels.""" for j in range(256 * iterations): for i in range(strip.numPixels()): strip.setPixelColor(i, wheel( (int(i * 256 / strip.numPixels()) + j) & 255)) strip.show() time.sleep(wait_ms / 1000.0) def theaterChaseRainbow(strip, wait_ms=50): """Rainbow movie theater light style chaser animation.""" for j in range(256): for q in range(3): for i in range(0, strip.numPixels(), 3): strip.setPixelColor(i + q, wheel((i + j) % 255)) strip.show() time.sleep(wait_ms / 1000.0) for i in range(0, strip.numPixels(), 3): strip.setPixelColor(i + q, 0) # Main program logic follows: if __name__ == '__main__': # Process arguments parser = argparse.ArgumentParser() parser.add_argument('-c', '--clear', action='store_true', help='clear the display on exit') args = parser.parse_args() # Create NeoPixel object with appropriate configuration. strip = PixelStrip(LED_COUNT, LED_PIN, LED_FREQ_HZ, LED_DMA, LED_INVERT, LED_BRIGHTNESS, LED_CHANNEL) # Intialize the library (must be called once before other functions). strip.begin() print('Press Ctrl-C to quit.') if not args.clear: print('Use "-c" argument to clear LEDs on exit') try: while True: print('Color wipe animations.') colorWipe(strip, Color(255, 0, 0)) # Red wipe colorWipe(strip, Color(0, 255, 0)) # Blue wipe colorWipe(strip, Color(0, 0, 255)) # Green wipe print('Theater chase animations.') theaterChase(strip, Color(127, 127, 127)) # White theater chase theaterChase(strip, Color(127, 0, 0)) # Red theater chase theaterChase(strip, Color(0, 0, 127)) # Blue theater chase print('Rainbow animations.') rainbow(strip) rainbowCycle(strip) theaterChaseRainbow(strip) except KeyboardInterrupt: if args.clear: colorWipe(strip, Color(0, 0, 0), 10) ``` 參考資料 1. 樂鷹計算機工作室[樹莓派控制WS2812B燈帶 - Python](https://www.dellts.cn/article/88.html)