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I have been working on a project that will allow me to take picture using a switch. So for that purpose i setup the GPIO and all necesseary tools for that code, Python-dev and etc.

When i run the code to control only the LED it works perfectly, i press the button, the LED turns on, and when i let go of the switch the LED turns off.

However the issue starts when i try to add the camera module to the code, when i add all other stuff like take a picture and prompt ls -l, the code does not wait for me to press the switch, instead it takes picture itself over and over again. I am am using rpi2 with latest version of raspian.

FYI I updated and upgraded the raspberry pi2.

What am i doing wrong? here is the code

import picamera
import time
import RPi.GPIO as GPIO
import subprocess
from subprocess import call


#def main():

GPIO.setwarnings(False)
GPIO.setmode(GPIO.BOARD)
GPIO.setup(11, GPIO.IN, pull_up_down=GPIO.PUD_DOWN) #pull down 
GPIO.setup(7, GPIO.OUT) #setup the LED for Processing
GPIO.output(7,0)

def blink():
    GPIO.output(7,1)
    time.sleep(1)
    GPIO.output(7,0)
    time.sleep(1)

def camera():
    subprocess.call(["sudo", "python", "cameratest.py"])    
    call(["ls", "-l"])

try:
    while True:
        if GPIO.input(11) == 1:  #gpio input first button
            blink()
            camera()
        else:
            GPIO.output(7,0) #if button false turn down the$
except KeyboardInterrupt:
        GPIO.cleanup()
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I think i found a solution firstly, I found that I can not use double quote on the subprocess so the format should be

subprocess.call (['sudo', 'nano', 'etc ')

and the answer to my question is I had to wait for the switch to be activate something like this

While True:
  GPIO.wait_for_edge(11, FALLING)
  time.sleep(1)
  if GPIO.input(11):

etc...
  • 1
    Quotes are a red herring. Python and Linux should be happy with both single and double quotes. Try print(subprocess.call(["echo", "world", 'a b c', "def", ' g hij'])) – joan Mar 9 '15 at 8:43

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