基本用法
以下示例演示了 GPIO Zero 库的部分功能。请注意,所有配方都是假设 Python 3 编写的。在 Python 2 下可能也能运行,但并不保证!
导入 GPIO Zero
在 Python 中,脚本中使用的库和函数必须在文件顶部按名称导入,Python 默认内置的函数除外。
例如,要使用 GPIO Zero 中的 Button
接口,必须明确导入:
from gpiozero import Button
现在 Button
可以直接在脚本中使用了:
button = Button(2)
或者,也可以导入整个 GPIO Zero 库:
import gpiozero
在这种情况下,对 GPIO Zero 中所有项目的引用都必须加上前缀:
button = gpiozero.Button(2)
引脚编号
该库的 GPIO 引脚使用 Broadcom (BCM) 引脚编号,而非物理 (BOARD) 编号。与 RPi.GPIO 库不同的是,它不可配置。不过,可以通过为引脚编号提供前缀来转换其他方案(见下文)。
下图中任何标有 GPIO
的引脚都可以用作引脚编号。例如,如果 LED 连接到 GPIO17
,则应将引脚编号指定为 17
,而不是 11
:
如果希望使用物理(BOARD)编号,则可将引脚编号指定为 BOARD11
。如果您熟悉 wiringPi 引脚编号(另一种物理布局),可以使用 WPI0
来代替。最后,还可以将引脚指定为 header:number
(头:编号),例如 J8:11
表示头 J8(现代 Pis 上的 GPIO 头)上的物理引脚 11
。因此,以下几行都是等价的:
led = LED(17)
led = LED("GPIO17")
led = LED("BCM17")
led = LED("BOARD11")
led = LED("WPI0")
led = LED("J8:11")
请注意,这些备用方案只是转换。如果您在命令行上请求设备状态,相关引脚编号将始终以 Broadcom (BCM) 方案报告:
led = LED("BOARD11")
led
<gpiozero.LED object on pin GPIO17, active_high=True, is_active=False>
在本手册中,我们将按照上图所示的 Broadcom (BCM) 布局使用默认的整数引脚编号。
LED (LED
)
反复打开和关闭 LED
:
from gpiozero import LED
from time import sleep
red = LED(17)
while True:
red.on()
sleep(1)
red.off()
sleep(1)
或者
from gpiozero import LED
from signal import pause
red = LED(17)
red.blink()
pause()
Python 脚本结束时会终止进程,GPIO 可能会被重置。请使用 signal.pause()
使脚本继续运行。更多信息,请参阅 如何保持脚本运行?
亮度可变的 LED
任何普通 LED 都可以使用 PWM(脉宽调制)设置其亮度值。在 GPIO Zero 中,可以使用 PWMLED
(亮度值在 0 和 1 之间)来实现这一功能:
from gpiozero import PWMLED
from time import sleep
led = PWMLED(17)
while True:
led.value = 0 # off
sleep(1)
led.value = 0.5 # half brightness
sleep(1)
led.value = 1 # full brightness
sleep(1)
与连续闪亮和熄灭类似,PWMLED
也可以脉冲(连续淡入淡出):
from gpiozero import PWMLED
from signal import pause
led = PWMLED(17)
led.pulse()
pause()
按钮 (Button
)
检查 Button
是否被按下:
from gpiozero import Button
button = Button(2)
while True:
if button.is_pressed:
print("Button is pressed")
else:
print("Button is not pressed")
等待按下按钮后再继续:
from gpiozero import Button
button = Button(2)
button.wait_for_press()
print("Button was pressed")
每次按下按钮都运行一个功能:
from gpiozero import Button
from signal import pause
def say_hello():
print("Hello!")
button = Button(2)
button.when_pressed = say_hello
pause()
请注意,button.when_pressed = say_hello
这一行并不运行 say_hello
函数,而是创建一个指向按下按钮时要调用的函数的引用。意外使用 button.when_pressed = say_hello()
,会将 when_pressed
操作设置为 None
(该函数的返回值),这意味着按下按钮时什么也不会发生。
同样,按钮释放也可以附加功能:
from gpiozero import Button
from signal import pause
def say_hello():
print("Hello!")
def say_goodbye():
print("Goodbye!")
button = Button(2)
button.when_pressed = say_hello
button.when_released = say_goodbye
pause()
按钮 控制 LED
按下 Button
时打开 LED
:
from gpiozero import LED, Button
from signal import pause
led = LED(17)
button = Button(2)
button.when_pressed = led.on
button.when_released = led.off
pause()
或者
from gpiozero import LED, Button
from signal import pause
led = LED(17)
button = Button(2)
led.source = button
pause()
按钮 控制 摄像头
使用 button.when_pressed = camera.capture
来触发 PiCamera
拍照是行不通的,因为 capture()
方法需要一个 输出
参数。不过,可以使用无需参数的自定义函数来实现:
from gpiozero import Button
from picamera import PiCamera
from datetime import datetime
from signal import pause
button = Button(2)
camera = PiCamera()
def capture():
camera.capture(f'/home/pi/{datetime.now():%Y-%m-%d-%H-%M-%S}.jpg')
button.when_pressed = capture
pause()
另一个例子是使用一个按钮来启动和停止摄像头预览,另一个按钮用来捕捉:
from gpiozero import Button
from picamera import PiCamera
from datetime import datetime
from signal import pause
left_button = Button(2)
right_button = Button(3)
camera = PiCamera()
def capture():
camera.capture(f'/home/pi/{datetime.now():%Y-%m-%d-%H-%M-%S}.jpg')
left_button.when_pressed = camera.start_preview
left_button.when_released = camera.stop_preview
right_button.when_pressed = capture
pause()
关机按钮
Button
类还提供了在按住按钮一定时间后运行函数的功能。本示例将在按住按钮 2 秒时关闭 Raspberry Pi:
from gpiozero import Button
from subprocess import check_call
from signal import pause
def shutdown():
check_call(['sudo', 'poweroff'])
shutdown_btn = Button(17, hold_time=2)
shutdown_btn.when_held = shutdown
pause()
LED板 (LEDBoard
)
使用 LEDBoard
可以访问 LED 集合:
from gpiozero import LEDBoard
from time import sleep
from signal import pause
leds = LEDBoard(5, 6, 13, 19, 26)
leds.on()
sleep(1)
leds.off()
sleep(1)
leds.value = (1, 0, 1, 0, 1)
sleep(1)
leds.blink()
pause()
使用 pwm=True
的 LEDBoard
可以控制每个 LED 的亮度:
from gpiozero import LEDBoard
from signal import pause
leds = LEDBoard(5, 6, 13, 19, 26, pwm=True)
leds.value = (0.2, 0.4, 0.6, 0.8, 1.0)
pause()
在 高级 LEDBoard 方案 中查看更多 LEDBoard
示例。
LED条形图 (LEDBarGraph
)
使用 LEDBarGraph
可以像条形图一样处理 LED 集合:
from gpiozero import LEDBarGraph
from time import sleep
graph = LEDBarGraph(5, 6, 13, 19, 26, 20)
graph.value = 1 # (1, 1, 1, 1, 1, 1)
sleep(1)
graph.value = 1/2 # (1, 1, 1, 0, 0, 0)
sleep(1)
graph.value = -1/2 # (0, 0, 0, 1, 1, 1)
sleep(1)
graph.value = 1/4 # (1, 0, 0, 0, 0, 0)
sleep(1)
graph.value = -1 # (1, 1, 1, 1, 1, 1)
sleep(1)
由于 LED 只能在 pwm=False
时开启或关闭(默认值),因此数值基本上是四舍五入的。
不过,在 pwm=True
时使用 LEDBarGraph
可以使用 LED 亮度获得更精确的数值:
from gpiozero import LEDBarGraph
from time import sleep
graph = LEDBarGraph(5, 6, 13, 19, 26, pwm=True)
graph.value = 1/10 # (0.5, 0, 0, 0, 0)
sleep(1)
graph.value = 3/10 # (1, 0.5, 0, 0, 0)
sleep(1)
graph.value = -3/10 # (0, 0, 0, 0.5, 1)
sleep(1)
graph.value = 9/10 # (1, 1, 1, 1, 0.5)
sleep(1)
graph.value = 95/100 # (1, 1, 1, 1, 0.75)
sleep(1)
LED字符显示屏 (LEDCharDisplay
)
使用 LEDCharDisplay
(实际上支持任意数量的显示段),可以用普通的 7 段显示 来表示各种字符:
from gpiozero import LEDCharDisplay
from time import sleep
display = LEDCharDisplay(21, 20, 16, 22, 23, 24, 12, dp=25)
for char in '321GO':
display.value = char
sleep(1)
display.off()
或者
from gpiozero import LEDCharDisplay
from signal import pause
display = LEDCharDisplay(21, 20, 16, 22, 23, 24, 12, dp=25)
display.source_delay = 1
display.source = '321GO '
pause()
在 高级 LEDBoard 方案 中查看更多多字符示例。
交通信号灯 (TrafficLights
)
完整的交通灯系统
使用像 Pi-Stop 这样的 TrafficLights
套件:
from gpiozero import TrafficLights
from time import sleep
lights = TrafficLights(2, 3, 4)
lights.green.on()
while True:
sleep(10)
lights.green.off()
lights.amber.on()
sleep(1)
lights.amber.off()
lights.red.on()
sleep(10)
lights.amber.on()
sleep(1)
lights.green.on()
lights.amber.off()
lights.red.off()
或者
from gpiozero import TrafficLights
from time import sleep
from signal import pause
lights = TrafficLights(2, 3, 4)
def traffic_light_sequence():
while True:
yield (0, 0, 1) # green
sleep(10)
yield (0, 1, 0) # amber
sleep(1)
yield (1, 0, 0) # red
sleep(10)
yield (1, 1, 0) # red+amber
sleep(1)
lights.source = traffic_light_sequence()
pause()
使用 LED
组件:
from gpiozero import LED
from time import sleep
red = LED(2)
amber = LED(3)
green = LED(4)
green.on()
amber.off()
red.off()
while True:
sleep(10)
green.off()
amber.on()
sleep(1)
amber.off()
red.on()
sleep(10)
amber.on()
sleep(1)
green.on()
amber.off()
red.off()
组合设计
按钮定格
每次按下按钮时,摄像头模块都会拍摄一张照片:
from gpiozero import Button
from picamera import PiCamera
button = Button(2)
camera = PiCamera()
camera.start_preview()
frame = 1
while True:
button.wait_for_press()
camera.capture(f'/home/pi/frame{frame:03d}.jpg')
frame += 1
请参阅 按钮定格 获取完整资源。
反应游戏
当看到灯亮起时,最先按下按钮的人获胜!
from gpiozero import Button, LED
from time import sleep
import random
led = LED(17)
player_1 = Button(2)
player_2 = Button(3)
time = random.uniform(5, 10)
sleep(time)
led.on()
while True:
if player_1.is_pressed:
print("Player 1 wins!")
break
if player_2.is_pressed:
print("Player 2 wins!")
break
led.off()
请参阅 快速反应游戏 获取完整资源。
GPIO音乐盒
每个按钮都会发出不同的声音!
from gpiozero import Button
import pygame.mixer
from pygame.mixer import Sound
from signal import pause
pygame.mixer.init()
button_sounds = {
Button(2): Sound("samples/drum_tom_mid_hard.wav"),
Button(3): Sound("samples/drum_cymbal_open.wav"),
}
for button, sound in button_sounds.items():
button.when_pressed = sound.play
pause()
请参阅 GPIO音乐盒 获取完整资源。
按下时全部打开
FishDish
:
按下按钮时,蜂鸣器和所有指示灯都会亮起。
from gpiozero import FishDish
from signal import pause
fish = FishDish()
fish.button.when_pressed = fish.on
fish.button.when_released = fish.off
pause()
Ryanteck TrafficHat
:(译注:由 Ryanteck 出品的 交通灯 小板)
from gpiozero import TrafficHat
from signal import pause
th = TrafficHat()
th.button.when_pressed = th.on
th.button.when_released = th.off
pause()
使用 LED
,Buzzer
,和 Button
组件:
from gpiozero import LED, Buzzer, Button
from signal import pause
button = Button(2)
buzzer = Buzzer(3)
red = LED(4)
amber = LED(5)
green = LED(6)
things = [red, amber, green, buzzer]
def things_on():
for thing in things:
thing.on()
def things_off():
for thing in things:
thing.off()
button.when_pressed = things_on
button.when_released = things_off
pause()
全彩LED (RGBLED
)
用 RGBLED
制作色彩:
from gpiozero import RGBLED
from time import sleep
led = RGBLED(red=9, green=10, blue=11)
led.red = 1 # full red
sleep(1)
led.red = 0.5 # half red
sleep(1)
led.color = (0, 1, 0) # full green
sleep(1)
led.color = (1, 0, 1) # magenta
sleep(1)
led.color = (1, 1, 0) # yellow
sleep(1)
led.color = (0, 1, 1) # cyan
sleep(1)
led.color = (1, 1, 1) # white
sleep(1)
led.color = (0, 0, 0) # off
sleep(1)
# slowly increase intensity of blue
for n in range(100):
led.blue = n/100
sleep(0.1)
运动传感器 (MotionSensor
)
当 MotionSensor
(运动传感器) 检测到运动时,点亮 LED
:
from gpiozero import MotionSensor, LED
from signal import pause
pir = MotionSensor(4)
led = LED(16)
pir.when_motion = led.on
pir.when_no_motion = led.off
pause()