【Raspberry Pi入门】PWM

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(12, GPIO.OUT)# set GPIO 25 as output for white led  
  
white = GPIO.PWM(12, 60)    # create object white for PWM on port 25 at 60 Hertz    
  
red.start(0)              # start white led on 0 percent duty cycle (off)  
  
# 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 = 0.02           # 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  
            red.ChangeDutyCycle(i)    
            sleep(pause_time)  
        for i in range(100,-1,-1):      # from 100 to zero in steps of -1  
            red.ChangeDutyCycle(i)  
            sleep(pause_time)  
  
except KeyboardInterrupt:  
    red.stop()              # stop the red PWM output  
    GPIO.cleanup()          # clean up GPIO on CTRL+C exit  
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