GPIO on a Neo

[Andy]

Hy

 

I tried to play around with the GPIOs and found some nice threads here however I don't get past the

modprobe gpio

command. I get this error

modprobe: FATAL: Module gpio not found in directory /lib/modules/4.14.29-sunxi64

 

Does my kernel build has no GPIO library inside?

Linux 4.14.29-sunxi64 #64 SMP Sat Mar 24 11:13:51 CET 2018 aarch64 GNU/Linux
 

Andy

 

 

[Larry Bank]

The sysfs driver should be loaded by default to access GPIOs. You can test it by running my ArmbianIO project:

 

https://github.com/bitbank2/ArmbianIO

 

 

[Andy]

thx hmm I installed it but I get:

Unrecognized board type, aborting...
AIOInit error

 

I tried to launch the ledtest.py script

 

When I look the board up in the /run/machine.id file its a "Nanopi Neo Plus 2" and this is not listed in the 

armbianio.c file. So what can I do? (the real board is a "NanoPi Neo Core 2")

 

Andy

 

 

[Larry Bank]

If you can find the pinout for that board's header, I'll add it

[guidol]

7 hours ago, Larry Bank said:

If you can find the pinout for that board's header, I'll add it

for the NanoPi Neo Core2 the pinout is here:

http://wiki.friendlyarm.com/wiki/index.php/NanoPi_NEO_Core2#Diagram.2C_Layout_and_Dimension

 

and for the NanoPi Neo Plus 2 here:

http://wiki.friendlyarm.com/wiki/index.php/NanoPi_NEO_Plus2#Diagram.2C_Layout_and_Dimension

[Andy]

So can you implement thees pins (for the Neo Core2 and Neo Plus 2)?

 

I used the http://wiki.friendlyarm.com/wiki/index.php/NanoPi_NEO_Core2#Diagram.2C_Layout_and_Dimension link and tried to blink an LED:

I used the UART1_TX / GPIOG6 Pin. This is the Linux Pin 198. And it works!

# echo "198" >/sys/class/gpio/export
# echo "out" >/sys/class/gpio/gpio198/direction
# echo "1" > /sys/class/gpio/gpio198/value

Now it would be great if I could use this in a Python script

 

Andy

 

[guidol]

6 hours ago, Andy said:

 

# echo "198" >/sys/class/gpio/export
# echo "out" >/sys/class/gpio/gpio198/direction
# echo "1" > /sys/class/gpio/gpio198/value

Now it would be great if I could use this in a Python script

 

 

 

how about a system-call?

import os
os.system('echo "198" >/sys/class/gpio/export')
os.system('echo "out" >/sys/class/gpio/gpio198/direction')
os.system('echo "1" > /sys/class/gpio/gpio198/value')

 

[Andy]

yes I did already try this however without root permission it does not work.

 

I tired then to add this to the rule file

SUBSYSTEM=="gpio*", PROGRAM="/bin/sh -c 'chown -R root:gpio /sys/class/gpio && chmod -R 770 /sys/class/gpio; chown -R root:gpio /sys/devices/virtual/gpio && chmod -R 770 /sys/devices/virtual/gpio; chown -R root:gpio /sys/devices/platform/soc/*.gpio/gpio && chmod -R 770 /sys/devices/platform/soc/*.gpio/gpio'"

 

And add my user to the GPIO group created before but still I get Permission denied for the direction command...

 

How can I get permission to execute the Python file without being root -s?

 

Andy 

[richardk]

10 hours ago, Andy said:

So can you implement thees pins (for the Neo Core2 and Neo Plus 2)?

 

I used the http://wiki.friendlyarm.com/wiki/index.php/NanoPi_NEO_Core2#Diagram.2C_Layout_and_Dimension link and tried to blink an LED:

I used the UART1_TX / GPIOG6 Pin. This is the Linux Pin 198. And it works!

# echo "198" >/sys/class/gpio/export
# echo "out" >/sys/class/gpio/gpio198/direction
# echo "1" > /sys/class/gpio/gpio198/value

Now it would be great if I could use this in a Python script

 

Andy

 

In Python:

  o = open("/sys/class/gpio/export", "w"); o.write("198");  o.close()

  o = open("/sys/class/gpio/gpio198/direction", "w"); o.write("out"); o.close()

  o = open("/sys/class/gpio/gpio198/value", "w"); o.write("1"); o.close()

 

[Andy]

1 hour ago, richardk said:

In Python:

  o = open("/sys/class/gpio/export", "w"); o.write("198");  o.close()

  o = open("/sys/class/gpio/gpio198/direction", "w"); o.write("out"); o.close()

  o = open("/sys/class/gpio/gpio198/value", "w"); o.write("1"); o.close()

 

 

Thx richard but same problem. No permission for the command "/sys/class/gpio/gpio198/direction"

See post above...

 

Andy

[richardk]

Just now, Andy said:

 

Thx richard but same problem. No permission for the command "/sys/class/gpio/gpio198/direction"

See post above...

 

Andy

Oh - okay.

 

If Debian, then "sudo adduser debian gpio" will add "gpio" privileges to user "debian", then log out and back in so the change takes effect.

 

[Andy]

4 hours ago, Andy said:

And add my user to the GPIO group created before but still I get Permission denied for the direction command...

 

I have already done that but still no success....

Traceback (most recent call last):
  File "testGPIO.py", line 13, in <module>
    open('/sys/class/gpio/gpio198/direction', 'w').write('out')
IOError: [Errno 13] Permission denied: '/sys/class/gpio/gpio198/direction'

 

Andy

[guidol]

37 minutes ago, Andy said:

 

I have already done that but still no success....

 

maybe python does not run as your user?
what is the output of
 

import os
os.system('id')

and then try to give gpio permission to this user?

[Andy]

this is the output:

 

uid=1000(deldro) gid=1000(deldro) groups=1000(deldro),20(dialout),27(sudo),29(audio),44(video),46(plugdev),101(systemd-journal),108(netdev),112(ssh),1001(gpio)

 

Andy

 

 

[guidol]

9 minutes ago, Andy said:

this is the output:

 

uid=1000(deldro) gid=1000(deldro) groups=1000(deldro),20(dialout),27(sudo),29(audio),44(video),46(plugdev),101(systemd-journal),108(netdev),112(ssh),1001(gpio)

 

user deldro seems already to be in the group gpio:

uid=1000(deldro) gid=1000(deldro) groups= 1001(gpio)

 

So I got no other idea

[Andy]

the problem seems the permission command.

I used the 

chown -R root:gpio /sys/class/gpio

 

However after boot it does not set properly.

I put this command in the /etc/rc.local file is this the wrong place?

 

Andy

 

[martinayotte]

1 hour ago, Andy said:

I put this command in the /etc/rc.local file is this the wrong place?

It must be placed before the last line showing "exit 0"

 

[Andy]

yes of course  but generally its in the right file?

[Andy]

after booting it seems that the permissions are set correctly:

 

ls -l /sys/class/gpio/
total 0
--w--w---- 1 root gpio 4096 Mar 27 21:17 export
lrwxrwxrwx 1 root gpio    0 Mar 27 21:17 gpiochip0 -> ../../devices/platform/soc/1c20800.pinctrl/gpio/gpiochip0
lrwxrwxrwx 1 root gpio    0 Mar 27 21:17 gpiochip352 -> ../../devices/platform/soc/1f02c00.pinctrl/gpio/gpiochip352
--w------- 1 root gpio 4096 Mar 27 21:17 unexport

However when I run the Python code I get permission denied for the open('/sys/class/gpio/gpio198/direction', 'w').write('out') command.

 

When I now type again the same command as written in the /etc/rc.local (chown -R root:gpio /sys/class/gpio) in the terminal

and relaunch the python script it does work! (ls -l /sys/class/gpio/ shows the same result as right after the booting)

Why do I need to set the permission twice??

 

Andy

 

 

 

[martinayotte]

Doing "chown -R root:gpio /sys/class/gpio" is only changing this directory, not the pointed symlinks, so you probably need to do a "chown -R root:gpio /sys/devices/platform/soc/1c20800.pinctrl/gpio" also...

 

[guidol]

10 hours ago, guidol said:

user deldro seems already to be in the group gpio:

uid=1000(deldro) gid=1000(deldro) groups= 1001(gpio)

 

a next idea from tonight - as I did see the user deldro is also sudo-user, maybe the echo does work with sudo?

import os
os.system('sudo echo "198" >/sys/class/gpio/export')
os.system('sudo echo "out" >/sys/class/gpio/gpio198/direction')
os.system('sudo echo "1" > /sys/class/gpio/gpio198/value')

 

[Andy]

sorry guys still same error.

 

However when I run the script with sudo and enter the password then it works.

However I need to run this script as "normal" user (deldro) which is also a sudo-user.

I could add the python to visudo to not ask for a password when using "sudo python...) but

I think this is not the "right" solution...

 

Andy

[windysea]

This would be a function of sysfs.  You'lll note that you are able to write to /sys/class/gpio/export without error (after changing permissions).  This triggers the new creation of /sys/class/gpio/gpioXX using default sysfs permissions.  You would need to do the chmod after writing to the export, and not before (IE: during boot).

 

The gpio sysfs module would need to support configuration of ownerships and permissions for new creations to change this.

[Andy]

hmm and what about a python library like the one from bitbank2 (ArmbianIO).

Would this solve the problem?

 

Andy