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I have a simple script I found that I'm using to deactivate xscreensaver via PIR motion sensor. It's using nearly 40% of my CPU when it runs. How can I calm it down?

#!/usr/bin/env python
import RPi.GPIO as GPIO
import os
GPIO.setwarnings(False)
GPIO.setmode(GPIO.BCM)
GPIO.setup(17, GPIO.IN)
while True:
    if GPIO.input(17): # Waits for motion signal from PIR on GPIO pin 17 then complete rest and exit
        print ("deactivating screensaver")
        os.system("xscreensaver-command -deactivate")
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1 Answer 1

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Right now you are looping as fast as the CPU can process the loop. Try adding a sleep to back off the CPU. It is unlikely that you need to check the motion sensor as often as you are

#!/usr/bin/env python

import RPi.GPIO as GPIO
import os
import time

GPIO.setwarnings(False)
GPIO.setmode(GPIO.BCM)
GPIO.setup(17, GPIO.IN)
while True:
    if GPIO.input(17): # Waits for motion signal from PIR on GPIO pin 17 then complete rest and exit
        print ("deactivating screensaver")
        os.system("xscreensaver-command -deactivate")
    time.sleep(1) # sleeps for 1 second
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  • I'm not so familiar with this but isn't there a possibility with exceptions?
    – Ingo
    Feb 24, 2018 at 18:53
  • @ingo possibility of what? Feb 24, 2018 at 18:55
  • I mean, maybe there is a way to use exceptions in python instead of polling with sleep. I don't know if RPi.GPIO can raise exceptions, maybe with use of built-in Exceptions?
    – Ingo
    Feb 25, 2018 at 12:55
  • 1
    @Ingo: No... Exceptions are for when bad things happen. The keyword you're looking for is interrupts.
    – Jacobm001
    Feb 26, 2018 at 4:29
  • @Jacobm001 Yes, in higher programming languages interrupts are called exception because there is more done than interrupt a program flow by the cpu, jump to a interrupt vector and push the program status to the stack ;-) And exceptions not only used for error conditions. But we get off topic ...
    – Ingo
    Feb 26, 2018 at 9:44

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