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