Re: [microblaze-uclinux] Questions about the uClinux GPIO-Driver

[j.pfefferl@xxxxxxxxx (Dr. Johann Pfefferl)]

Hello Nadine,

here is a little program I have written to test the GPIO functionality:

----------------------- snip ----------------------------------------
#include <fcntl.h>
#include <string.h>
#include <unistd.h>
#include <errno.h>
#include <sys/ioctl.h>
#include <linux/ibm_ocp_gpio.h>

int main(void)
{
  int r, gpio_dev;
  if(0 < (gpio_dev = open("/dev/xgpio", O_RDWR))) {
    struct ibm_gpio_ioctl_data gpio_info;
    memset(&gpio_info, 0, sizeof(gpio_info));
    gpio_info.device = 0; /* Read the first gpio subdevice */
    /* Mark all pins as input */
    gpio_info.mask = ~0;
    if(0 > (r = ioctl(gpio_dev, IBMGPIO_TRISTATE, &gpio_info)))
      perror("ioctl IBMGPIO_TRISTATE failed: %s", g_strerror(errno));

    while(1) {
      gpio_info.device = 0; /* Read the first gpio subdevice */
      if(0 > (r = ioctl(gpio_dev, IBMGPIO_IN, &gpio_info)))
        perror("ioctl failed: r=%d errno=%d %s", r, errno, strerror(errno));
      else
        printf("gpio_info: device=%d mask=%x data=0x%x\n", gpio_info.device, gpio_info.mask, gpio_info.data);
      usleep(100000);
    }
  }
  close(gpio_dev);
  return 0;
}
----------------------- snip ----------------------------------------

It handles only the input of data. If you want to output something you
have to set the data into the variable

gpio_info.data = 0xblablabla;

and then perform a IBMGPIO_OUT ioctl.

You must set the TRISTATE mask correctly to get input/output working
correctly for one GPIO subdevice!!!

Hope this helps,
  Johann Pfefferl

Nadine Seyberlich <Serina16@xxxxxxx> wrote:
> Hi all,
> 
> i'm writing my diploma thesis, where i have to use the SUZAKU-S (SZ130-U00) with the Microblaze and uClinux as basis. To the Board over the GPIO Pins is external hardware connected.
> I have seen that there is a ready GPIO-Driver in uClinux. How can I use this driver? 
> How can I respond the driver from a C-Program? Can the GPIO pins be addressed directly or do I have to write a separate module for the adressing? How complex is this way? Does someone have a sample program, where I can see the use of the GPIO driver?
> 
> Thanks for your help.
> 
> Nadine
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-- 
Dr. Johann Pfefferl   ------------   mailto j.pfefferl at eubus dot net
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==
 -o)   A computer program does what you tell it to do,
 /\\        not what you want it to do.               
_\_v-                                                 

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