Qt-creator problem: error: 'gpio26' was not declared in this scope

J Offline

Thank You very much.
Works fine now !

J Offline

One more question.
The program needs to be root to access gpio. I think thats not the best way. How to change that?

S Offline

Hi,

Depending on how the device presents itself, one possibility would be to change the group of the gpio device and add your user to that group

J Offline

I try that but did not realy works.
I build a group 'hwuser'
add the user to the group

change the group with

chgrp -R hwuser /sys/class

with ls -l could see that it is done.

but after reboot the group is root again.

S Offline

I thought you were accessing the GPIO through a /dev device or does the sys fs entry point to a device ?

Anyway, sys (like /dev in general) is generated dynamically so that method won't work.

If you are indeed accessing a device that can be found in /dev, you could try to setup an udev rule that sets the group of that device.

T Offline

That is more Linux question than Qt specific. If your target Linux uses udev for device handling then you need to specify rules which states you want "hwuser" group for gpio. Example setting udev-rules for gpio in raspberry pi: http://www.raspberrypi.org/phpBB3/viewtopic.php?f=29&t=9667

J Offline

Ok thanks to all.
I figured out now.

Thats works for me:
sudo nano /etc/udev/rules.d/99-gpio.rules
paste:
SUBSYSTEM==”gpio”, ACTION==”add”, PROGRAM=”/bin/sh -c ‘chown -R [user]:[group] /sys%p’”
PROGRAM=”/bin/sh -c ‘chown -R [user]:[group] /sys/class’”

save and reboot

S Offline

That might be a little too radical not to say that it's a security breach. Just modify the file you use not the entire tree

J Offline

ok I will test that.

thx

J Offline

it is mysterious,
after reboot export gpio works fine but set direction fails.

the same again on root works fine.

S Offline

Are you accessing several files ?

J Offline

not sure what You mean.

thats the init of the gpio

gpio26 = new GPIOClass("26"); //create new GPIO object

gpio26->export_gpio(); //export GPIO26


gpio26->setdir_gpio("out"); //GPIO26 set to output

the export works, I can see it after start program

i have made a button to set direction... thats works to

i have made button for export unexport and set direction.

thats works fine too