
                         OMAP GPIO API's HowTo
                         =====================

This document is a short summary how to use OMAP Linux GPIO API. It is
mainly focussed on OMAP5912 OSK, but should fit with extensions (more
or less GPIOs) to other OMAP processors as well.

If anything is missing, is wrong, needs extension or update, please send
update to Linux-omap-open-source@linux.omap.com.

I. GPIO Modules/Banks
---------------------

OMAP5912 OSK has 64 GPIOs (general purpose IO pins). These are organized
in four modules (banks) with 16 pins each. OMAP GPIO API doesn't distinguish
between modules and numbers the pins from 0 - 63:

A) GPIO MODULE/BANK 0 - PIN  0-15
B) GPIO MODULE/BANK 1 - PIN 16-31
C) GPIO MODULE/BANK 2 - PIN 32-47
D) GPIO MODULE/BANK 3 - PIN 48-63

See

http://www-s.ti.com/sc/psheets/spru767a/spru767a.pdf

for more details.

II. GPIO API's
--------------

A) Include

#include <asm/arch/gpio.h>

B) omap_cfg_reg(xxxx);

Description: Configure pin mux.

Parameter: Pin to be configured for GPIO.

Note: This function may only be necessary for some GPIO pins. Because OMAP
      chip itself has less real hardware pins than necessary to use all
      its functionality at the same time, some pins share different
      functions (called pin multiplexing, short pin mux). E.g. one pin may
      be used for serial interface *or* GPIO. Check if this is the case for
      the GPIO you want to use and if you have to configure the pin mux.

C) omap_request_gpio(int gpio)

Description: Request GPIO to be used.

Parameter: int gpio - GPIO PIN (Pin 0-63)

Note: Using this function, you dont have to worry about banks/modules where
      the gpio pin is.

D) omap_set_gpio_direction(int gpio, int is_input)

Description: This function is responsible for setting the gpio pin direction
             (input or output).

Parameter: int gpio - GPIO PIN (Pin 0-63)
           int is_input - pin direction (0 = output, 1 = input)

E) omap_set_gpio_dataout(int gpio, int enable)

Description: This function is responsible for writing to a pin.

Parameter: int gpio - GPIO PIN (Pin 0-63)
           int enable - pin value (0 or 1)

F) omap_get_gpio_datain(int gpio)

Description: This function is responsible for reading pin values.

Parameter: int gpio - GPIO PIN (Pin 0-63)

G) omap_free_gpio(int gpio)

Description: This function is responsible for freeing the pin used.

Parameter: int gpio - GPIO PIN (Pin 0-63)

H) OMAP_GPIO_IRQ(int gpio)

Description: Returns the Interrupt number for the specified gpio pin.

Parameter: int gpio - GPIO PIN (Pin 0-63)

I) set_irq_type(unsigned int irq, unsigned int type)

Description: This function is responsible for setting the type of interrupt
             (RISING or FALLING).

Parameter: unsigned int irq - The interrupt number for the gpio pin.
           unsigned int type - (IRQT_RISING = rising, IRQT_FALLING= falling)


III. Example
------------

1) Writing to gpio pin#3 a value 1 and reading the value of gpio pin#3.

#include <asm/arch/gpio.h>

int ret;                       /* Return value */

omap_request_gpio(3);          /* Request for gpio pin */
omap_set_gpio_direction(3,0);
omap_set_set_dataout(3,1);     /* Writing a 1 to gpio pin # 3: */
ret = omap_get_datain(3);      /* Reading the value of pin # 3 */
printk("value of pin # 3 = %d\n",ret);
omap_free_gpio(3);             /* Freeing gpio pin # 3 */

2) Interrupt input by gpio pin#3

#include <asm/arch/gpio.h>

omap_request_gpio(3);         /* Request for gpio pin */
omap_set_gpio_direction(3,0);
set_irq_type(OMAP_GPIO_IRQ(3),IRQT_RISING); /* Setting up pin for interrupt */
request_irq(OMAP_GPIO_IRQ(3), (void *)&my_int_handler, SA_SHIRQ,....);

...                         /* Do stuff, handle interrupts in my_int_handler */

free_irq(OMAP_GPIO_IRQ(3),&id); /*  Freeing interrupt and gpio pin */
omap_free_gpio(3);

------------------------------------------------------------------
Last modified 14. August 2006
The OMAP Linux Kernel Team
Arnold <abo_gwapo@yahoo.com>
Dirk Behme <dirk.behme@gmail.com>

                         OMAP GPIO API's HowTo
                         =====================

This document is a short summary how to use OMAP Linux GPIO API. It is
mainly focussed on OMAP5912 OSK, but should fit with extensions (more
or less GPIOs) to other OMAP processors as well.

If anything is missing, is wrong, needs extension or update, please send
update to Linux-omap-open-source@linux.omap.com.

I. GPIO Modules/Banks
---------------------

OMAP5912 OSK has 64 GPIOs (general purpose IO pins). These are organized
in four modules (banks) with 16 pins each. OMAP GPIO API doesn't distinguish
between modules and numbers the pins from 0 - 63:

A) GPIO MODULE/BANK 0 - PIN  0-15
B) GPIO MODULE/BANK 1 - PIN 16-31
C) GPIO MODULE/BANK 2 - PIN 32-47
D) GPIO MODULE/BANK 3 - PIN 48-63

See

http://www-s.ti.com/sc/psheets/spru767a/spru767a.pdf

for more details.

II. GPIO API's
--------------

A) Include

#include <asm/arch/gpio.h>

B) omap_cfg_reg(xxxx);

Description: Configure pin mux.

Parameter: Pin to be configured for GPIO.

Note: This function may only be necessary for some GPIO pins. Because OMAP
      chip itself has less real hardware pins than necessary to use all
      its functionality at the same time, some pins share different
      functions (called pin multiplexing, short pin mux). E.g. one pin may
      be used for serial interface *or* GPIO. Check if this is the case for
      the GPIO you want to use and if you have to configure the pin mux.

C) omap_request_gpio(int gpio)

Description: Request GPIO to be used.

Parameter: int gpio - GPIO PIN (Pin 0-63)

Note: Using this function, you dont have to worry about banks/modules where
      the gpio pin is.

D) omap_set_gpio_direction(int gpio, int is_input)

Description: This function is responsible for setting the gpio pin direction
             (input or output).

Parameter: int gpio - GPIO PIN (Pin 0-63)
           int is_input - pin direction (0 = output, 1 = input)

E) omap_set_gpio_dataout(int gpio, int enable)

Description: This function is responsible for writing to a pin.

Parameter: int gpio - GPIO PIN (Pin 0-63)
           int enable - pin value (0 or 1)

F) omap_get_gpio_datain(int gpio)

Description: This function is responsible for reading pin values.

Parameter: int gpio - GPIO PIN (Pin 0-63)

G) omap_free_gpio(int gpio)

Description: This function is responsible for freeing the pin used.

Parameter: int gpio - GPIO PIN (Pin 0-63)

H) OMAP_GPIO_IRQ(int gpio)

Description: Returns the Interrupt number for the specified gpio pin.

Parameter: int gpio - GPIO PIN (Pin 0-63)

I) set_irq_type(unsigned int irq, unsigned int type)

Description: This function is responsible for setting the type of interrupt
             (RISING or FALLING).

Parameter: unsigned int irq - The interrupt number for the gpio pin.
           unsigned int type - (IRQT_RISING = rising, IRQT_FALLING= falling)


III. Example
------------

1) Writing to gpio pin#3 a value 1 and reading the value of gpio pin#3.

#include <asm/arch/gpio.h>

int ret;                       /* Return value */

omap_request_gpio(3);          /* Request for gpio pin */
omap_set_gpio_direction(3,0);
omap_set_set_dataout(3,1);     /* Writing a 1 to gpio pin # 3: */
ret = omap_get_datain(3);      /* Reading the value of pin # 3 */
printk("value of pin # 3 = %d\n",ret);
omap_free_gpio(3);             /* Freeing gpio pin # 3 */

2) Interrupt input by gpio pin#3

#include <asm/arch/gpio.h>

omap_request_gpio(3);         /* Request for gpio pin */
omap_set_gpio_direction(3,0);
set_irq_type(OMAP_GPIO_IRQ(3),IRQT_RISING); /* Setting up pin for interrupt */
request_irq(OMAP_GPIO_IRQ(3), (void *)&my_int_handler, SA_SHIRQ,....);

...                         /* Do stuff, handle interrupts in my_int_handler */

free_irq(OMAP_GPIO_IRQ(3),&id); /*  Freeing interrupt and gpio pin */
omap_free_gpio(3);

------------------------------------------------------------------
Last modified 14. August 2006
The OMAP Linux Kernel Team
Arnold <abo_gwapo@yahoo.com>
Dirk Behme <dirk.behme@gmail.com>
