#!/usr/bin/python
# -*- coding: UTF-8 -*-

import RPi.GPIO as GPIO
import time

#led灯的物理引脚
channel=32

GPIO.setmode(GPIO.BOARD)
GPIO.setwarnings(False)
GPIO.setup(channel, GPIO.OUT, initial=GPIO.LOW)

pwm = GPIO.PWM(channel, 50)
pwm.start(0)
try:
    while True:
        #led灯慢慢变亮
        for duty in range(100, 0, -4):
            pwm.ChangeDutyCycle(duty)
            time.sleep(0.1)

        #led灯慢慢变暗
        for duty in range(0, 100, 4):
            pwm.ChangeDutyCycle(duty)
            time.sleep(0.1)

except KeyboardInterrupt:
    pass

#GPIO资源清理
pwm.stop()
GPIO.cleanup()