From mboxrd@z Thu Jan  1 00:00:00 1970
From: "Azhar Mr." <shaik.azharuddin@yahoo.co.in>
Subject: Peculiar Behaviour of the GPIO Program
Date: Fri, 23 Nov 2007 06:35:19 +0000 (GMT)
Message-ID: <74079.72407.qm@web7604.mail.in.yahoo.com>
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Dear all,
  =20
  I am working on OMAP5912 OSK.
  =20
  I am trying to write a simple GPIO Program to write a value =911=92 to =
a particular free GPIO Pin. For that I had written a program led_glow.c g=
iven below.
  =20
  /* define any of the valid GPIO pins as LED_GPIO */
  #define LED_GPIO 18
  =20
  =20
  /* Defines the value written to the pin defined as LED_GPIO */
  =20
  #define LED_STATUS 1
  =20
  MODULE_LICENSE("Dual BSD/GPL");
  =20
  =20
  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;
        }
       =20
        /* setting LED_GPIO as output pin */
  =20
       omap_set_gpio_direction(LED_GPIO,0);
  =20
        /* writing to LED_GPIO the value of LED_STATUS */
  =20
        omap_set_gpio_dataout(LED_GPIO,LED_STATUS);
  =20
        /* printing the value of LED_GPIO pin */
  =20
  printk("value of pin # %d =3D %d\n",LED_GPIO,omap_get_gpio_datain(LED_G=
PIO));
  =20
        return 0;
  }
  =20
  void cleanup_module(void)
  {
        omap_free_gpio(LED_GPIO);    =20
  printk("[SUCCESS]: LED_GLOW Module unregistered successfull.\n");
  }
  =20
  =20
  I included our led_glow.c as a module in the Linux-2.6.22/drivers/leds =
directory .
  =20
  Then using arm-linux-gcc compiler, I compiled the led_glow.c code to ob=
tain led_glow.ko
  =20
  Then using the insmod I inserted the module led_glow.ko in the
  OSK5912 Environment.
  =20
  I tested the module with various free GPIO-Pins of Expansion connector =
'C'
  =20
  For some GPIO pins it is able to write the value '1' and for some pins =
it is unable to write '1'
  =20
  Sh-3.00# value of pin #15 =3D 1
  Sh-3.00# value of pin #16 =3D 1
  Sh-3.00# value of pin #17=3D 0
  Sh-3.00# value of pin #20 =3D 0
  =20
  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
  =20
  I don=92t understand this peculiar behavior of my GPIO-CODE.
  =20
  Please Help
  =20
  With Regards
  =20
  Azhar

      =20
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