gpio.c File Reference

GPIO general purpose interface code for both file system and mmap() control of GPIOs. More...

#include <stdio.h>
#include <stdint.h>
#include <unistd.h>
#include <stdlib.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <errno.h>
#include <string.h>
#include "bbbandroidHAL.h"

Classes
struct	GPIOBit_t

Macros
#define	TOTAL_PINS_PER_HEADER   46
#define	GPIO_DATA_OUT_REG   0x13C
#define	GPIO_DATA_IN_REG   0x138
#define	GPIO_OE_REG   0x134
#define	SYSFS_GPIO_DIR   "/sys/class/gpio"

Functions
int	openGPIO (const int useMmap)
static int	readGPIOMmap (const GPIOBit_t *pinGPIO)
static int	writeGPIOMmap (const GPIOBit_t *pinGPIO, const unsigned int value)
static int	readGPIOFS (const GPIOBit_t *pinGPIO)
static int	writeGPIOFS (const GPIOBit_t *pinGPIO, const unsigned int value)
int	readGPIO (const unsigned int header, const unsigned int pin)
int	writeGPIO (const unsigned int header, const unsigned int pin, const unsigned int value)
void	closeGPIO (void)

Variables
static char	fsBuf [64]
static GPIOBit_t	P8_GPIO_pin_info [TOTAL_PINS_PER_HEADER]
static GPIOBit_t	P9_GPIO_pin_info [TOTAL_PINS_PER_HEADER]
static const uint32_t	gpioAddrs []
static uint32_t *	mapGPIO [4]
static int	fdGPIO = 0
static int	initialized = 0
static int	usingMmap = 0

Detailed Description

GPIO general purpose interface code for both file system and mmap() control of GPIOs.

Author

Ankur Yadav (ankur.nosp@m.ayad.nosp@m.av@gm.nosp@m.ail..nosp@m.com), Andrew Henderson (hende.nosp@m.rsa@.nosp@m.iccul.nosp@m.us.o.nosp@m.rg)

Macro Definition Documentation

#define GPIO_DATA_IN_REG   0x138

GPIO DATA IN register address

#define GPIO_DATA_OUT_REG   0x13C

GPIO DATA OUT register address

#define GPIO_OE_REG   0x134

GPIO OE register address

#define SYSFS_GPIO_DIR   "/sys/class/gpio"

File system path to access GPIO

#define TOTAL_PINS_PER_HEADER   46

Total number of pins per header in beaglebone black

Function Documentation

void closeGPIO

(

void

)

For closing file descriptor if accessed using file system and set initialized to 0.

int openGPIO

(

const int

useMmap

)

This function takes parameter input useMmap to take choice if you want to use Memory Map to access GPIO or to access it using file system. If using memory map then a proper file descriptor is set.

Parameters

useMmap

a constant integer argument.

Returns

If successful then 0 is returned and if it fails then 1 is returned.

int readGPIO	(	const unsigned int	header,
		const unsigned int	pin
	)

It takes input GPIO header and pin and reads its value after opening its file. If Memory Map is used then proper bit value is read using the file descriptor initialized in openGPIO() function call. Proper bit positions for all the GPIOs are present in GPIOBit_t arrays of each P8 and P9 header.

Parameters

header	a constant unsigned int argument.
pin	a constant unsigned int argument.

See Also

readGPIOMmap()

readGPIOFS()

Returns

1 if read 1 and 0 if read 0;

static int readGPIOFS ( const GPIOBit_t *  pinGPIO )

static

This function takes input pointer to GPIOBit_t type structure which stores information about a pin. This pin information is then used to get pin id to read from GPIO.

Parameters

*pinGPIO

a constant GPIOBit_t argument.

Returns

1 if read 1 and 0 if read 0;

static int readGPIOMmap ( const GPIOBit_t *  pinGPIO )

static

This function takes input pointer to GPIOBit_t type structure which stores information about a pin. This pin information is then used to get DATA IN register and read the GPIO.

Parameters

*pinGPIO

a constant GPIOBit_t argument.

Returns

The bit for the GPIO that we're interested in.

int writeGPIO	(	const unsigned int	header,
		const unsigned int	pin,
		const unsigned int	value
	)

It takes input GPIO header, pin and value that is required to be set on GPIO after opening corresponding GPIO file. If Memory Map is used then proper bit value is set using the file descriptor initialized in openGPIO() function call. Proper bit positions for all the GPIOs are present in GPIOBit_t arrays of each P8 and P9 header.

Parameters

header	a constant unsigned int argument.
pin	a constant unsigned int argument.

See Also

writeGPIOMmap()

writeGPIOFS()

Returns

0 if successfull and 1 if it fails

static int writeGPIOFS ( const GPIOBit_t *  pinGPIO, const unsigned int  value  )

static

This function takes input pointer to GPIOBit_t type structure which stores information about a pin. This pin information is then used to get pin id to write to GPIO.

Parameters

*pinGPIO

a constant GPIOBit_t argument.

Returns

0 if successfull and 1 if it fails

static int writeGPIOMmap ( const GPIOBit_t *  pinGPIO, const unsigned int  value  )

static

This function takes input pointer to GPIOBit_t type structure which stores information about a pin. This pin information is then used to get DATA OUT register and OE register to write to GPIO.

Parameters

*pinGPIO

a constant GPIOBit_t argument.

Returns

0

Variable Documentation

int fdGPIO = 0

static

File descriptor for GPIO for file system access

char fsBuf[64]

static

Buffer to store generated file system path using snprintf

const uint32_t gpioAddrs[]

static

Initial value:

= 
  { 0x44E07000, 0x4804C000, 0x481AC000, 0x481AE000 }

Register Bank addresses

int initialized = 0

static

Variable to check if GPIO is initialized earlier

uint32_t* mapGPIO[4]

static

Variable for GPIO memory map

GPIOBit_t P8_GPIO_pin_info[TOTAL_PINS_PER_HEADER]

static

static GPIOBit_t variable to store P8 header pins.

GPIOBit_t P9_GPIO_pin_info[TOTAL_PINS_PER_HEADER]

static

static GPIOBit_t variable to store P9 header pins.

int usingMmap = 0

static

Variable to check if Memory map access mode for GPIO is set