Python“关机/重启树莓派”脚本，使用单个按钮

Question

我从这里得到了一段 Python 代码： http://www.raspberry-pi-geek.com/Archive/2013/01/Adding-an-On-Off-switch-to-your-Raspberry-Pi

我想改进它。

由于这是我第一次使用 Python，所以我一直无法理解实际发生的情况。

代码如下：

# Import the modules to send commands to the system and access GPIO pins
from subprocess import call
import RPi.GPIO as gpio
from time import sleep

gpio.setmode(gpio.BCM) # Set pin numbering to board numbering
gpio.setup(22, gpio.IN) # Set up pin 22 as an input

rebootBool = 0

# Define a function to keep script running
def main(pin):
    while True:
        #gpio.remove_event_detect(pin)
        gpio.add_event_detect(22, gpio.RISING, callback=confirmation, bouncetime=200) # Set up an interrupt to look for button presses
        sleep(5000000)

def confirmation(pin):
    gpio.remove_event_detect(pin)
    gpio.add_event_detect(22, gpio.RISING, callback=shutdown, bouncetime=200)
    sleep(3) # if button has been pressed again within 3 seconds, shut down will happen
    main(22)

def reboot(pin):
    rebootBool = 1
    call('reboot', shell=False)
    exit(0)

# Define a function to run when an interrupt is called
def shutdown(pin):
    gpio.remove_event_detect(pin)
    gpio.add_event_detect(22, gpio.RISING, callback=reboot, bouncetime=200)
    sleep(3) # if the button has been pressed for a third time, within 3 seconds, Pi will reboot
    if rebootBool == 0: # Just to make sure a halt is not called after the 3 seconds have passed, if reboot is called
        call('halt', shell=False)
    exit(0)

main(22) # Run the loop function to keep script running

我想做的是这样的：

• 如果按钮被按下一次，则会执行确认功能，如果在 3 秒内按下按钮，则会重置按钮以调用关机功能。
  • 否则，使用主循环继续
• 在关机函数中，如果再次按下（3秒内），它会重置以调用重启函数。
  • 否则继续，然后关闭

会发生什么：

如果我按下按钮两次或三次，它会告诉我 gpio.add_event_detect 已经定义，当它尝试在 main() 中定义它时。 所以它不会改变它，如果我再按一次它，它就会调用关闭函数。

我不明白的是：

为什么它要在 main 中定义 gpio 事件，而实际功能是重新启动或关闭（它应该调用重新启动或关闭）？

Answer 1

因为回调函数在单独的线程中运行。这意味着，例如，当您在主循环中调用任何回调函数时，它仍然有效（主循环），因此当您从回调函数（线程＃1）和主循环调用函数 gpio.add_event_detect 时会发生这种情况（线程＃2）同时。这是典型的比赛条件。 您可以通过运行以下代码来检查它：

#!/usr/bin/python
# Import the modules to send commands to the system and access GPIO pins
from subprocess import call
import RPi.GPIO as gpio
from time import sleep

gpio.setmode(gpio.BCM) # Set pin numbering to board numbering
gpio.setup(22, gpio.IN, pull_up_down=gpio.PUD_DOWN) # Set up pin 22 as an input

rebootBool = 0

# Define a function to keep script running
def main(pin):
    while True:
        print "main loop"
        gpio.remove_event_detect(22)
        gpio.add_event_detect(22, gpio.RISING, callback=confirmation, bouncetime=200) # Set up an interrupt to look for button presses
        sleep(1)
        #raw_input()

def confirmation(pin):
    print "confirmation1"
    sleep(5)
    print "confirmation2"
    gpio.remove_event_detect(22)
    gpio.add_event_detect(22, gpio.RISING, callback=shutdown, bouncetime=200)
    sleep(5) # if button has been pressed again within 3 seconds, shut down will happen
    gpio.remove_event_detect(22)
    main(22)

def reboot(pin):
    rebootBool = 1
    print "reboot"
    #call('reboot', shell=False)
    exit(0)

# Define a function to run when an interrupt is called
def shutdown(pin):
    print "shutdown"
    gpio.remove_event_detect(pin)
    gpio.add_event_detect(22, gpio.RISING, callback=reboot, bouncetime=200)
    sleep(3) # if the button has been pressed for a third time, within 3 seconds, Pi will reboot
    if rebootBool == 0: # Just to make sure a halt is not called after the 3 seconds have passed, if reboot is called
        #call('halt', shell=False)
        print "halt"
    exit(0)

main(22) # Run the loop function to keep script running

Answer 2

因此，在 Anton Glukhov 向我解释了要注意什么之后，我发现了如何解决每个问题，现在它可以完美运行。

这是更好地解释我所做的链接： http://sourceforge.net/p/raspberry-gpio-python/wiki/Inputs/

不幸的是，除了在 main 函数中使用 while 循环之外，我无法做到这一点。 但由于没有发生任何重要的事情，因此每个循环都添加了 1 秒的睡眠时间，以确保最小的 CPU 使用率。

我在这里分享最终代码，希望它可以帮助其他人：

# Import the modules to send commands to the system and access GPIO pins
from subprocess import call
import RPi.GPIO as gpio
from time import sleep
from os import system

gpio.setmode(gpio.BCM) # Set pin numbering to BCM numbering
gpio.setup(22, gpio.IN) # Set up pin 22 as an input

def confirmation(pin):
    #print "Confirmation Function on pin %d" % pin
    system('echo Press again to confirm Shut down menu! | wall -n') # let all logged in users know
    gpio.remove_event_detect(pin)
    gpio.add_event_detect(pin, gpio.RISING, bouncetime=200)
    sleep(2) # if button has been pressed again within 2 seconds, shut down function is called
    if gpio.event_detected(pin):
        shutdown(pin)
    else:
        #print "canceled"
        system('echo Shut down canceled! | wall -n') # let all logged in users know
        main()

def resetPin(pin):
    #print "Pin %d has been reset" % pin
    gpio.remove_event_detect(pin)
    gpio.add_event_detect(pin, gpio.RISING, bouncetime=200)

def reboot(pin):
    #print "Reboot Function on pin %d" % pin
    call('reboot', shell=False)
    exit(0)

# Define a function to run when an interrupt is called
def shutdown(pin):
    #print "ShutDown function on pin %d" % pin
    system('echo Press again if you want to reboot instead of shut down! | wall -n') # let all logged in users know
    gpio.remove_event_detect(pin)
    gpio.add_event_detect(pin, gpio.RISING, bouncetime=200)
    sleep(2) # if the button has been pressed for a third time, within 2 seconds, Pi will reboot
    if gpio.event_detected(pin):
        reboot(pin)
    else:
        call('halt', shell=False)
        exit(0)

# Define a function to keep script running
def main():
    #print "Main Function"
    resetPin(22)
    while True:
        sleep(1)
        if gpio.event_detected(22):
            confirmation(22)

main() # Run the main function to keep script running