GPIO from python user space OPi:GPIO app

arhi · September 21, 2017

I have seen this old thread but since last post was long time ago and it was shell based I decided to go with new one ...

I have the udev setup (you can see some old versions inside commented out too)

root@orangepizeroplus2:~# cat /etc/udev/rules.d/60-python-pifacecommon.rules
#KERNEL=="spidev*", GROUP="gpio", MODE="0660"
#SUBSYSTEM=="gpio*", ACTION=="add|change", RUN+="/usr/bin/find /sys/class/gpio -exec /bin/chmod g+u {} + -exec /bin/chown :gpio {} +"


#KERNEL=="gpio*", GROUP="gpio", MODE="0660"
#SUBSYSTEM=="gpio*", ACTION=="add|change", RUN+="/usr/bin/find /sys/class/gpio -exec /bin/chmod g+u {} + -exec /bin/chown :gpio {} +"

KERNEL=="spidev*", GROUP="gpio", MODE="0660"
KERNEL=="gpio*", MODE:="0660", GROUP:="gpio"
SUBSYSTEM=="gpio*", PROGRAM="/bin/sh -c '\
 chown -R root:gpio /sys/class/gpio ; \
 chmod -R 777 /sys/class/gpio ;\
 chown -R root:gpio /sys/devices/virtual/gpio ;\
 chmod -R 777 /sys/devices/virtual/gpio; \
 chown -R root:gpio /sys/devices/platform/soc/*.gpio/gpio ;\
 chmod -R 777 /sys/devices/platform/soc/*.gpio/gpio; \
 chmod -R 777 /sys/class/gpio/gpio1/* ;\
 chgrp gpio /sys/class/gpio/gpio1/* ;\
 chgrp -R gpio /sys/devices/platform/sunxi-pinctrl/gpio ;\
 chmod -R ug+rw /sys/devices/platform/sunxi-pinctrl/gpio ' "


#SUBSYSTEM=="gpio", PROGRAM="/bin/sh -c '/bin/chown -R root:gpio /sys/devices/soc.0/*pinctrl/gpio'"
#SUBSYSTEM=="gpio", PROGRAM="/bin/sh -c '/bin/chmod -R ug+rw /sys/devices/soc.0/*pinctrl/gpio'"
root@orangepizeroplus2:~#

and when I do it step by step from shell I kinda get it working but a simple

GPIO.setmode(GPIO.BOARD)
GPIO.setup(self.pin, GPIO.IN)

fails .. depending on the number of restarts it fails on /sys/class/gpio/gpio1/direction or in one other file there ..

python user is in gpio group, all files are 777...

IOError: [Errno 13] Permission denied: '/sys/class/gpio/gpio1/direction'
root@orangepizeroplus2:~# ls -la /sys/class/gpio/gpio1/direction
-rwxrwxrwx 1 root gpio 4096 Sep 21 07:52 /sys/class/gpio/gpio1/direction

looks like some race, OPi:GPIO is trying to access them faster then udev is chowning and chmoding files... I'm banging my head for days no more ideas

system is:

Welcome to ARMBIAN 5.32 user-built Debian GNU/Linux 8 (jessie) 3.4.113-sun8i

root@orangepizeroplus2:~# uname -a
Linux orangepizeroplus2 3.4.113-sun8i #4 SMP PREEMPT Thu Sep 21 03:24:39 CEST 2017 armv7l GNU/Linux

I can change the system to any other one (other kernel, other whatever..) if that will help, I was going with the older kernel hoping this will solve the problem, having identical problem with

Welcome to ARMBIAN 5.27 stable Debian GNU/Linux 8 (jessie) 4.10.11-sun8i
root@orangepione:~# uname -a
Linux orangepione 4.10.11-sun8i #2 SMP Tue Apr 18 17:55:20 CEST 2017 armv7l GNU/Linux

so, if anyone have any idea what to try I'd really appreciate some help

arhi · September 21, 2017

forgot to say, originally the error was on export but added to rclocal echo1 > export and that triggers the udev rule so now is stuck opn direction

olivluca · September 21, 2017

This patch solves it for me (Edit but I think there should be a better way)

diff --git a/OPi/GPIO.py b/OPi/GPIO.py
index 775134e..aa8e77b 100644
--- a/OPi/GPIO.py
+++ b/OPi/GPIO.py
@@ -239,6 +239,7 @@ Methods
 """
 
 import warnings
+import time
 
 from OPi.constants import IN, OUT
 from OPi.constants import LOW, HIGH                     # noqa: F401
@@ -358,6 +359,7 @@ def setup(channel, direction, initial=None, pull_up_down=None):
             else:
                 raise e
 
+        time.sleep(0.1)
         sysfs.direction(pin, direction)
         _exports[channel] = direction
         if direction == OUT and initial is not None: