之前介绍过RPI.GPIO 模块的脉宽调制（PWM）功能，并且实现了呼吸灯的效果。本文更进一步，加入了多个呼吸灯并且用不同的步调间歇发光。
电路连接

程序源码

#!/usr/bin/env python2.7

import RPi.GPIO as GPIO # always needed with RPi.GPIO
from time import sleep # pull in the sleep function from time module

GPIO.setmode(GPIO.BOARD) # choose BCM or BOARD numbering schemes. I use BCM

GPIO.setup(26, GPIO.OUT)# set GPIO 25 as output for white led
GPIO.setup(24, GPIO.OUT)# set GPIO 24 as output for red led

white = GPIO.PWM(26, 100) # create object white for PWM on port 25 at 100 Hertz
red = GPIO.PWM(24, 100) # create object red for PWM on port 24 at 100 Hertz

white.start(0) # start white led on 0 percent duty cycle (off)
red.start(100) # red fully on (100%)

now the fun starts, we'll vary the duty cycle to

dim/brighten the leds, so one is bright while the other is dim

pause_time = 0.01 # you can change this to slow down/speed up

try:
while True:
for i in range(0,101): # 101 because it stops when it finishes 100
white.ChangeDutyCycle(i)
red.ChangeDutyCycle(100 - i)
sleep(pause_time)
for i in range(100,-1,-1): # from 100 to zero in steps of -1
white.ChangeDutyCycle(i)
red.ChangeDutyCycle(100 - i)
sleep(pause_time)

except KeyboardInterrupt:
white.stop() # stop the white PWM output
red.stop() # stop the red PWM output
GPIO.cleanup() # clean up GPIO on CTRL+C exit

保存为 led.py 之后，运行
sudo python led.py
就能看到两个LED间歇性呼吸的效果了。