gpio error

[tinashe]

can you please help
i am using raspberry pi 3b with Emeria.os (embbed android os).
my super user permission request is working fine the problem is that i can not access the gpio files.

I art : Late-enabling -Xcheck:jni
W System : ClassLoader referenced unknown path:
I QtCore : Start
W linker : /data/app/org.qtproject.example-1/lib/arm/libQt5AndroidExtras.so: unsupported flags DT_FLAGS_1=0x80
W linker : /data/app/org.qtproject.example-1/lib/arm/libQt5Gui.so: unsupported flags DT_FLAGS_1=0x80
W linker : /data/data/org.qtproject.example/qt-reserved-files/plugins/platforms/android/libqtforandroid.so: unsupported flags DT_FLAGS_1=0x80
I Qt : qt started
I art : Do partial code cache collection, code=10KB, data=26KB
I art : After code cache collection, code=10KB, data=26KB
I art : Increasing code cache capacity to 128KB
E linker : normalize_path - invalid input: "C", the input path should be absolute
W linker : Warning: unable to normalize "C"
E linker : normalize_path - invalid input: "C", the input path should be absolute
W linker : Warning: unable to normalize "C"
I GRALLOC-MOD: Opening GPU0 module
D vc4-drm-winsys: vc4 screen creation <= 38
D vc4-drm-winsys: created new vc4 screen 40 => 0xa8fa6318
I GRALLOC-PIPE: Created a pipe manager for vc4 and fd 38
D vc4-drm-winsys: vc4 screen creation <= 43
D vc4-drm-winsys: created new vc4 screen 44 => 0xa8fa6a98
I OpenGLRenderer: Initialized EGL, version 1.4
D OpenGLRenderer: Swap behavior 1
W OpenGLRenderer: Failed to choose config with EGL_SWAP_BEHAVIOR_PRESERVED, retrying without...
D OpenGLRenderer: Swap behavior 0
D libconsole.so: Permission granted
D libconsole.so: Unable to open /sys/class/gpio/export
F libc : Fatal signal 11 (SIGSEGV), code 1, fault addr 0x4 in tid 5899 (RenderThread)
"org.qtproject.example" died.

#include <QCoreApplication>
#include <stdio.h>
#include <QDebug>
#ifdef Q_OS_ANDROID
#include <QtAndroidExtras>
#endif
#include <errno.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <unistd.h>

int export_pin(){

// Export the desired pin by writing to /sys/class/gpio/export

int fd = open("/sys/class/gpio/export", O_WRONLY);
if (fd == -1) {
    perror("Unable to open /sys/class/gpio/export");
     qDebug()<<"Unable to open /sys/class/gpio/export";
    exit(1);
}

if (write(fd, "24", 2) != 2) {
    perror("Error writing to /sys/class/gpio/export");
     qDebug()<<"Error writing to /sys/class/gpio/export";
    exit(1);

}

return fd;
}

int unexport_pin(){
// Unexport the pin by writing to /sys/class/gpio/unexport

int fd = open("/sys/class/gpio/unexport", O_WRONLY);

if (fd == -1) {
perror("Unable to open /sys/class/gpio/unexport");
qDebug()<<"Unable to open /sys/class/gpio/unexport";
exit(1);
}

if (write(fd, "24", 2) != 2) {
perror("Error writing to /sys/class/gpio/unexport");
qDebug()<<"Error writing to /sys/class/gpio/unexport";
exit(1);
}

return fd;

}

int main(int argc, char *argv[])
{
QCoreApplication a(argc, argv);

#ifdef Q_OS_ANDROID
    auto  result = QtAndroid::checkPermission(QString("android.permission.ACCESS_SUPERUSER"));
        if(result == QtAndroid::PermissionResult::Denied){
            QtAndroid::PermissionResultMap resultHash = QtAndroid::requestPermissionsSync(QStringList({"android.permission.ACCESS_SUPERUSER"}));
            if(resultHash["android.permission.ACCESS_SUPERUSER"] == QtAndroid::PermissionResult::Denied)
                qDebug()<< "Permission rejected";
        }
        else{

         qDebug()<<"Permission granted";

        int fd;

            fd = export_pin();
            close(fd);

            // Set the pin to be an output by writing "out" to /sys/class/gpio/gpio24/direction

            fd = open("/sys/class/gpio/gpio24/direction", O_WRONLY);
            if (fd == -1) {
                perror("Unable to open /sys/class/gpio/gpio24/direction");
                 qDebug()<<"Unable to open /sys/class/gpio/gpio24/direction";
                exit(1);
            }

            if (write(fd, "out", 3) != 3) {
                perror("Error writing to /sys/class/gpio/gpio24/direction");
                qDebug()<<"Error writing to /sys/class/gpio/gpio24/direction";
                exit(1);
            }

            close(fd);

            fd = open("/sys/class/gpio/gpio24/value", O_WRONLY);
            if (fd == -1) {
                perror("Unable to open /sys/class/gpio/gpio24/value");
                exit(1);
            }

            // Toggle LED 500 ms on and 500ms off forever

              while (1) {
                if (write(fd, "1", 1) != 1) {
                    perror("Error writing to /sys/class/gpio/gpio24/value");
                    exit(1);
                }
                else{

                  qDebug()<< "ON";
                }
                usleep(500000);

                if (write(fd, "0", 1) != 1) {
                    perror("Error writing to /sys/class/gpio/gpio24/value");
                    exit(1);
                }
                else{

                  qDebug()<< "OFF";
                }

                usleep(500000);
            }

            close(fd);

            fd = unexport_pin();

            close(fd);


        }
#endif


return a.exec();

}

[mrdebug]

I suggest you to use pigpio or wiringpi library in order to manage raspberry pi gpios.

[tinashe]

Thanks mrdebug
but i do not think it will work because i tried the following
code since /dev/gpiomem does not need root permission
int fd = open("/dev/gpiomem", O_RDONLY) ;

if (fd == -1) {

   qDebug()<<"Unable to open /dev/gpiomem";
  exit(1);

}
else{

  qDebug()<< "gpio /dev/gpiomem";

}
and still unable to access the file

[SGaist]

Hi,

Since you are using Emeria.os, you should ask their folks on whether these GPIO's are accessible and if so, how.

[tinashe]

This post is deleted!

[tinashe]

@SGaist
thank you for the reply
Sorry its Emteria.os
i was told to
the gpios are accessable
Make sure those files are accessible from your application. Check Linux file permissions. and how do i check for these permissions?

[jsulm]

@tinashe said in gpio error:

and how do i check for these permissions?

ls -lh /sys/class/gpio/unexport

You should read about UNIX/Linux basics.
To get access for the group your user is in:

chmod g+rw /sys/class/gpio/unexport

For user

chmod u+rw /sys/class/gpio/unexport

[tinashe]

@jsulm
thank you very much
how do i run this in my main file or c++ file because i have seen these commands run in cmd terminal.

[jsulm]

@tinashe said in gpio error:

how do i run this in my main file or c++ file because i have seen these commands run in cmd terminal

Why do you want to do it in your app? Just do it once in a terminal...
The commands I provided to set access rights need root access (via sudo for example):

sudo chmod g+rw /sys/class/gpio/unexport

So, your app will not be able to do this.
But you should really check how access rights are handled in Emteria.os

[tinashe]

@jsulm said in gpio error:

For user
unfortunately i can not do it on the terminal.
or can i do this in the cmd.txt found in boot folder?

[tinashe]

@jsulm
unfortunately the ssh server is locked for demo which am using currently

[jsulm]

@tinashe See "man 2 chmod".
But most probably your user will need to start the app as root (sudo for example).

[tinashe]

@tinashe

i was told to do permission seeting in /data/init.d

[tinashe]

@jsulm
chmod g+rw /sys/class/gpio/unexport
cd /etc/udev/rules.d/
touch local.rules
ACTION=="add", KERNEL=="gpio", MODE="0666"
and did notwork

[jsulm]

@tinashe This does not have anything to do with Qt now, please find out how to do this with Linux.

[tinashe]

@jsulm
thank you very much will do that