Peculiar Behaviour of the GPIO Program

* Peculiar Behaviour of the GPIO Program
@ 2007-11-23  6:35 Azhar Mr.
  2007-11-26 23:55 ` Krishna Prasad Herur
  0 siblings, 1 reply; 3+ messages in thread
From: Azhar Mr. @ 2007-11-23  6:35 UTC (permalink / raw)
  To: linux-omap-open-source

Dear all,

  I am working on OMAP5912 OSK.

  I am trying to write a simple GPIO Program to write a value ‘1’ to a particular free GPIO Pin. For that I had written a program led_glow.c given below.

  /* define any of the valid GPIO pins as LED_GPIO */
  #define LED_GPIO 18

  /* Defines the value written to the pin defined as LED_GPIO */

  #define LED_STATUS 1

  MODULE_LICENSE("Dual BSD/GPL");

  int init_module(void)
  {
        /* requesting for LED_GPIO */
        if(omap_request_gpio(LED_GPIO)<0)
        {
   printk("[ERROR]: Failed in allocating the requested GPIO Pin \n");
              return -1;
        }

        /* setting LED_GPIO as output pin */

       omap_set_gpio_direction(LED_GPIO,0);

        /* writing to LED_GPIO the value of LED_STATUS */

        omap_set_gpio_dataout(LED_GPIO,LED_STATUS);

        /* printing the value of LED_GPIO pin */

  printk("value of pin # %d = %d\n",LED_GPIO,omap_get_gpio_datain(LED_GPIO));

        return 0;
  }

  void cleanup_module(void)
  {
        omap_free_gpio(LED_GPIO);     
  printk("[SUCCESS]: LED_GLOW Module unregistered successfull.\n");
  }

  I included our led_glow.c as a module in the Linux-2.6.22/drivers/leds directory .

  Then using arm-linux-gcc compiler, I compiled the led_glow.c code to obtain led_glow.ko

  Then using the insmod I inserted the module led_glow.ko in the
  OSK5912 Environment.

  I tested the module with various free GPIO-Pins of Expansion connector 'C'

  For some GPIO pins it is able to write the value '1' and for some pins it is unable to write '1'

  Sh-3.00# value of pin #15 = 1
  Sh-3.00# value of pin #16 = 1
  Sh-3.00# value of pin #17= 0
  Sh-3.00# value of pin #20 = 0

  I tested all the free GPIO pins of EXPANSION CONEECTOR C, irrespective of the printed value at the GPIO Pins at all the GPIO Pins I can observe only '0' value in the C.R.O. I could not get any response in the C.R.O

  I don’t understand this peculiar behavior of my GPIO-CODE.

  Please Help

  With Regards

  Azhar

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