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Andy

GPIO access

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After reading several threads without success I need to ask again how I can get permission as a "normal" user to use the GPIO pins via my python script:

#!/usr/bin/python
import time

PIN_NUM = 200


print "GPIO %s" % PIN_NUM

try:
   # check to see if the pin is already exported
   open(''.join(['/sys/class/gpio/gpio',str(PIN_NUM),'/direction'])).read()
except:
   # it isn't, so export it   
   open('/sys/class/gpio/export', 'w').write(str(PIN_NUM))

# set gpiochip198 to output
open(''.join(['/sys/class/gpio/gpio',str(PIN_NUM),'/direction']), 'w').write('out')

for i in range(1000):
   open(''.join(['/sys/class/gpio/gpio',str(PIN_NUM),'/value']), 'w').write("1")
   time.sleep(0.5)
   open(''.join(['/sys/class/gpio/gpio',str(PIN_NUM),'/value']), 'w').write("0")
   time.sleep(0.5)

# remove GPIO87 folder from file system
open('/sys/class/gpio/unexport', 'w').write(str(PIN_NUM))

 

 

I get this error:

Traceback (most recent call last):
  File "testGPIO.py", line 17, in <module>
    open(''.join(['/sys/class/gpio/gpio',str(PIN_NUM),'/direction']), 'w').write('out')
IOError: [Errno 13] Permission denied: '/sys/class/gpio/gpio200/direction'

 

So I tried to add:

SUBSYSTEM=="gpio", ACTION=="add", RUN="/bin/sh -c '\
        chown -R root:gpio /sys/class/gpio && chmod -R 770 /sys/class/gpio;\
        chown -R root:gpio /sys$DEVPATH && chmod -R 770 /sys$DEVPATH\
'"

into /etc/udev/rules.d/90-gpiomem.rules

 

and yes my username is the GPIO group....

 

Can someone help me further...thx

 

Andy

 

 

 

 

 

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