gpio.c File Reference

GPIO library definitions using the /sys/class/gpio interface. More...

#include <sys/types.h>
#include <sys/stat.h>
#include <sys/time.h>
#include <sys/select.h>
#include <fcntl.h>
#include <unistd.h>
#include <stdio.h>
#include <errno.h>
#include <string.h>
#include "rnr/rnrconfig.h"
#include "rnr/log.h"
#include "rnr/gpio.h"

Go to the source code of this file.

Functions
static int	gpioReadDirection (int gpio)
	Read GPIO current direction. More...
static int	gpioReadEdge (int gpio)
	Read GPIO current edge trigger. More...
int	gpioExport (int gpio)
	Export (create) a GPIO interface. More...
int	gpioUnexport (int gpio)
	Unexport (delete) a GPIO interface. More...
int	gpioSetDirection (int gpio, int dir)
	Set GPIO signal direction. More...
int	gpioSetEdge (int gpio, int edge)
	Set GPIO edge trigger type. More...
int	gpioSetPull (int gpio, int pull)
	Set GPIO pull. More...
int	gpioProbe (int gpio, gpio_info_t *p)
	Safely probe GPIO parameters. More...
int	gpioRead (int gpio)
	Read GPIO pin's current value. More...
int	gpioWrite (int gpio, int value)
	Write GPIO value. More...
int	gpioNotify (int fd, double timeout)
	Notify on GPIO input value change. More...
int	gpioOpen (int gpio)
	Open GPIO pin. More...
int	gpioClose (int fd)
	Close GPIO pin. More...
int	gpioQuickRead (int fd)
	Quick read GPIO pin's current value. More...
int	gpioQuickWrite (int fd, int value)
	Quick write GPIO pin value. More...
int	gpioBitBang (int fd, byte_t pattern[], size_t bitCount, unsigned int usecIbd)
	Bit-bang bits out a GPIO pin. More...
void	gpioMakeDirname (int gpio, char buf[], size_t size)
	Make GPIO directory name. More...

Variables
static const char *	GpioRoot = "/sys/class/gpio"

Detailed Description

GPIO library definitions using the /sys/class/gpio interface.

LastChangedDate

2015-04-09 15:03:13 -0600 (Thu, 09 Apr 2015)

Rev

3916

Author

Robin Knight (robin.nosp@m..kni.nosp@m.ght@r.nosp@m.oadn.nosp@m.arrow.nosp@m.s.co.nosp@m.m)

Copyright

© 2015-2017. RoadNarrows LLC.
http://www.roadnarrows.com
All Rights Reserved

Definition in file gpio.c.

Function Documentation

int gpioBitBang	(	int	fd,
		byte_t	pattern[],
		size_t	bitCount,
		unsigned int	usecIbd
	)

Bit-bang bits out a GPIO pin.

Bits from pattern[0] ... pattern[N] sequentially drive the GPIO output pin. If bit == 0 then the pin is driven low, if bit == 1 then the pin is driven high.

The pattern buffer must be at least (bitCount + 7) / 8 bytes long. The bits in pattern[i] are read out in big-endian order b7 b6 ...

Between bit output, an inter-bit delay of usecIbd is enforced.

Method: sysfs

Parameters

fd	Open GPIO pin file descriptor.
pattern	Bit pattern buffer to bang. The bytes are big-endian.
bitCount	Count of bits to bang.
usecIbd	Inter-bit delay in microseconds. A 0 value means a fast as the architecture can bang.

Returns

On success OK(0) is returned, otherwise RC_ERROR(-1) is returned.

Definition at line 558 of file gpio.c.

References gpioQuickWrite().

Referenced by sysfsBitBang().

{
  size_t  byteCount = (bitCount + 7) / 8;
  size_t  i, j, k;
  int     mask, value;

  for(i=0, k=0; i<byteCount; ++i)
  {
    for(j=0, mask=0x80; j<8 && k<bitCount; ++j, ++k)
    {
      if( usecIbd > 0 )
      {
        usleep(usecIbd);
      }
      value = pattern[i] & mask? 1: 0;
      mask >>= 1;
      if( gpioQuickWrite(fd, value) < 0 )
      {
        return RC_ERROR;
      }
    }
  }

  return OK;
}

int gpioClose

(

int

fd

)

Close GPIO pin.

Method: sysfs

Parameters

fd	Open GPIO pin file descriptor.

Returns

On success OK(0) is returned, otherwise RC_ERROR(-1) is returned.

Definition at line 510 of file gpio.c.

Referenced by sysfsBitBang(), and sysfsRead().

{
  if( fd >= 0 )
  {
    close(fd);
  }

  return OK;
}

int gpioExport

(

int

gpio

)

Export (create) a GPIO interface.

The call requires root privaleges.

Method: sysfs

Parameters

gpio	The sysfs exported GPIO number.

Returns

On success OK(0) is returned, otherwise RC_ERROR(-1) is returned.

Definition at line 192 of file gpio.c.

Referenced by main().

{
  int   fd;
  char  buf[MAX_PATH]; 

  sprintf(buf, "%s/export", GpioRoot);

  if( (fd = open(buf, O_WRONLY)) < 0 )
  {
    LOGSYSERROR("open(\"%s\", O_WRONLY)", buf);
    return RC_ERROR;
  }

  sprintf(buf, "%d", gpio); 

  if( write(fd, buf, strlen(buf)) < 0 )
  {
    LOGSYSERROR("write(%d, \"%s\", %zu)", fd, buf, strlen(buf));
    close(fd);
    return RC_ERROR;
  }

  close(fd);

  LOGDIAG3("Exported GPIO %d interface.", gpio);

  return OK;
}

void gpioMakeDirname	(	int	gpio,
		char	buf[],
		size_t	size
	)

Make GPIO directory name.

Director name: /sys/class/gpio/gpio<gpio>

The base directory holds key special files such as value, direction, and edge.

Method: sysfs

Parameters

	gpio	The sysfs exported GPIO number.
[out]	buf	Buffer to hold directory name.
	size	Size of buffer in bytes.

Definition at line 587 of file gpio.c.

Referenced by main().

{
  snprintf(buf, size, "%s/gpio%d", GpioRoot, gpio);
  buf[size-1] = 0;
}

int gpioNotify	(	int	fd,
		double	timeout
	)

Notify on GPIO input value change.

This function blocks until 1) value has changed, 2) a timeout has occurred, or 3) an error was encoutered.

Method: sysfs

Parameters

fd	Open GPIO pin file descriptor.
timeout	Wait timeout. A value of 0.0 is no timeout.

Returns

On success the pin value 0 or 1 is returned. Otherwise RC_ERROR(-1) is returned. Use errno to determine error.

Definition at line 442 of file gpio.c.

References gpioQuickRead().

Referenced by mainInit().

{
  fd_set          efds;
  struct timeval  tv;
  int             rc;

  FD_ZERO(&efds);
  FD_SET(fd, &efds);

  // no timeout
  if( timeout <= 0.0 )
  {
    rc = select(fd+1, NULL, NULL, &efds, NULL);
  }
  else
  {
    tv.tv_sec  = (long)timeout;
    tv.tv_usec = (long)((timeout - (double)tv.tv_sec) * 1000000.0);
    if( tv.tv_usec > 1000000 )
    {
      ++tv.tv_sec;
      tv.tv_usec = 0;
    }
    //fprintf(stderr, "%lf --> %ld %ld\n", timeout, tv.tv_sec, tv.tv_usec);
    rc = select(fd+1, NULL, NULL, &efds, &tv);
  }

  // change
  if( rc > 0 )
  {
    LOGDIAG3("GPIO value changed.");
    rc = gpioQuickRead(fd);
  }

  // timeout
  else if( rc == 0 )
  {
    LOGDIAG3("GPIO watch timedout.");
    rc = gpioQuickRead(fd);
  }

  // error
  else
  {
    LOGSYSERROR("select(%d, ...)", fd);
  }

  return rc;
}

int gpioOpen

(

int

gpio

)

Open GPIO pin.

Leaving the file descriptor open allows for quick reads or writes. It is the responsibility of the user to close the file descriptor.

Method: sysfs

Parameters

gpio	The sysfs exported GPIO number.

Returns

On success the open file descriptor is returned. Otherwise RC_ERROR(-1) is returned.

Definition at line 492 of file gpio.c.

Referenced by mainInit(), sysfsBitBang(), and sysfsRead().

{
  int   fd;
  char  buf[MAX_PATH]; 

  sprintf(buf, "%s/gpio%d/value", GpioRoot, gpio);

  if( (fd = open(buf, O_RDWR)) < 0 )
  {
    LOGSYSERROR("open(\"%s\", O_RDWR)", buf);
    return RC_ERROR;
  }

  LOGDIAG3("Opened GPIO %d.", gpio);

  return fd;
}

int gpioProbe	(	int	gpio,
		gpio_info_t *	p
	)

Safely probe GPIO parameters.

Method: sysfs

Parameters

	gpio	The sysfs exported GPIO number.
[out]	p	GPIO info.

Returns

On success OK(0) is returned, otherwise RC_ERROR(-1) is returned.

Definition at line 346 of file gpio.c.

References gpio_info_t::dir, gpio_info_t::edge, gpio_info_t::gpio, GPIO_DIR_IN, GPIO_EDGE_NONE, GPIO_PULL_DS, gpioRead(), gpioReadDirection(), gpioReadEdge(), gpio_info_t::pin, gpio_info_t::pull, and gpio_info_t::value.

Referenced by sysfsProbe().

{
  int   v;
  int   rc = OK;

  p->gpio     = gpio;
  p->pin      = -1; // gpioExportedToPin(gpio);
  p->dir      = GPIO_DIR_IN;
  p->edge     = GPIO_EDGE_NONE;
  p->pull     = GPIO_PULL_DS;
  p->value    = 0;

  if( (v = gpioReadDirection(gpio)) < 0 )
  {
    rc = RC_ERROR;
  }
  else
  {
    p->dir = v;
  }

  if( (v = gpioReadEdge(gpio)) < 0 )
  {
    rc = RC_ERROR;
  }
  else
  {
    p->edge = v;
  }

  if( (v = gpioRead(gpio)) < 0 )
  {
    rc = RC_ERROR;
  }
  else
  {
    p->value = v;
  }

  return rc;
}

int gpioQuickRead

(

int

fd

)

Quick read GPIO pin's current value.

Method: sysfs

Parameters

fd	Open GPIO pin file descriptor.

Returns

On success the pin value 0 or 1 is returned. Otherwise RC_ERROR(-1) is returned.

Definition at line 520 of file gpio.c.

Referenced by gpioNotify(), mainInit(), and sysfsRead().

{
  char  c;

  // go to top of 'file'
  lseek(fd, 0, SEEK_SET);

  if( read(fd, &c, 1) < 0 )
  {
    LOGSYSERROR("read(%s, ...)", fd);
    return RC_ERROR;
  }

  LOGDIAG3("Read GPIO value %c.", c);

  return c == '0'? 0: 1;
}

int gpioQuickWrite	(	int	fd,
		int	value
	)

Quick write GPIO pin value.

Method: sysfs

Parameters

fd	Open GPIO pin file descriptor.
value	GPIO pin value. One of: 0 (low) or 1 (high).

Returns

On success OK(0) is returned, otherwise RC_ERROR(-1) is returned.

Definition at line 538 of file gpio.c.

Referenced by gpioBitBang().

{
  char    c;

  // go to top of 'file'
  lseek(fd, 0, SEEK_SET);

  c = value == 0? '0': '1';

  if( write(fd, &c, 1) < 0 )
  {
    LOGSYSERROR("write(%s, \"%c\", 1)", fd, c);
    return RC_ERROR;
  }

  LOGDIAG3("Wrote GPIO value %c.", c);

  return OK;
}

int gpioRead

(

int

gpio

)

Read GPIO pin's current value.

Method: sysfs

Parameters

gpio	The sysfs exported GPIO number.

Returns

On success the pin value 0 or 1 is returned. Otherwise RC_ERROR(-1) is returned.

Definition at line 388 of file gpio.c.

Referenced by gpioProbe().

{
  int   fd;
  char  buf[MAX_PATH]; 
  char  c;

  sprintf(buf, "%s/gpio%d/value", GpioRoot, gpio);

  if( (fd = open(buf, O_RDONLY)) < 0 )
  {
    LOGSYSERROR("open(\"%s\", O_RDONLY)", buf);
    return RC_ERROR;
  }

  if( read(fd, &c, 1) < 0 )
  {
    LOGSYSERROR("read(%s, ...)", fd);
    close(fd);
    return RC_ERROR;
  }

  LOGDIAG3("Read GPIO %d value %c.", gpio, c);

  return c == '0'? 0: 1;
}

static int gpioReadDirection ( int  gpio )

static

Read GPIO current direction.

Method: sysfs

Parameters

gpio	The sysfs exported GPIO number.

Returns

On success GPIO_DIR_IN(0) or GPIO_DIR_OUT(1) is returned.
Otherwise RC_ERROR(-1) is returned.

Definition at line 87 of file gpio.c.

References GPIO_DIR_IN, GPIO_DIR_IN_STR, GPIO_DIR_OUT, and GPIO_DIR_OUT_STR.

Referenced by gpioProbe().

{
  int     fd;
  char    buf[MAX_PATH]; 
  ssize_t n;

  sprintf(buf, "%s/gpio%d/direction", GpioRoot, gpio);

  if( (fd = open(buf, O_RDONLY)) < 0 )
  {
    LOGSYSERROR("open(\"%s\", O_WRONLY)", buf);
    return RC_ERROR;
  }

  if( (n = read(fd, buf, sizeof(buf))) < 0 )
  {
    LOGSYSERROR("read(%d, %p, %zu)", fd, buf, sizeof(buf));
    close(fd);
    return RC_ERROR;
  }

  close(fd);

  buf[n] = 0;

  if( !strncmp(buf, GPIO_DIR_IN_STR, strlen(GPIO_DIR_IN_STR)) )
  {
    return GPIO_DIR_IN;
  }
  else if( !strncmp(buf, GPIO_DIR_OUT_STR, strlen(GPIO_DIR_OUT_STR)) )
  {
    return GPIO_DIR_OUT;
  }
  else
  {
    LOGERROR("Unknown direction value: \"%s\".", buf);
    return RC_ERROR;
  }
}

static int gpioReadEdge ( int  gpio )

static

Read GPIO current edge trigger.

Method: sysfs

Parameters

gpio	The sysfs exported GPIO number.

Returns

On success GPIO_EDGE_NONE(0), GPIO_EDGE_RISING(1), GPIO_EDGE_FALLING(2), or GPIO_EDGE_BOTH(3) is returned.
Otherwise RC_ERROR(-1) is returned.

Definition at line 139 of file gpio.c.

References GPIO_EDGE_BOTH, GPIO_EDGE_BOTH_STR, GPIO_EDGE_FALLING, GPIO_EDGE_FALLING_STR, GPIO_EDGE_NONE, GPIO_EDGE_NONE_STR, GPIO_EDGE_RISING, and GPIO_EDGE_RISING_STR.

Referenced by gpioProbe().

{
  int     fd;
  char    buf[MAX_PATH]; 
  ssize_t n;

  sprintf(buf, "%s/gpio%d/edge", GpioRoot, gpio);

  if( (fd = open(buf, O_RDONLY)) < 0 )
  {
    LOGSYSERROR("open(\"%s\", O_WRONLY)", buf);
    return RC_ERROR;
  }

  if( (n = read(fd, buf, sizeof(buf))) < 0 )
  {
    LOGSYSERROR("read(%d, %p, %zu)", fd, buf, sizeof(buf));
    close(fd);
    return RC_ERROR;
  }

  close(fd);

  buf[n] = 0;

  if( !strncmp(buf, GPIO_EDGE_NONE_STR, strlen(GPIO_EDGE_NONE_STR)) )
  {
    return GPIO_EDGE_NONE;
  }
  else if( !strncmp(buf, GPIO_EDGE_RISING_STR, strlen(GPIO_EDGE_RISING_STR)) )
  {
    return GPIO_EDGE_RISING;
  }
  else if( !strncmp(buf, GPIO_EDGE_FALLING_STR, strlen(GPIO_EDGE_FALLING_STR)) )
  {
    return GPIO_EDGE_FALLING;
  }
  else if( !strncmp(buf, GPIO_EDGE_BOTH_STR, strlen(GPIO_EDGE_BOTH_STR)) )
  {
    return GPIO_EDGE_BOTH;
  }
  else
  {
    LOGERROR("Unknown edge value: \"%s\".", buf);
    return RC_ERROR;
  }
}

int gpioSetDirection	(	int	gpio,
		int	dir
	)

Set GPIO signal direction.

Method: sysfs

Parameters

gpio	The sysfs exported GPIO number.
dir	Direction. One of: GPIO_DIR_IN(0) GPIO_DIR_OUT(1)

Returns

On success OK(0) is returned, otherwise RC_ERROR(-1) is returned.

Definition at line 250 of file gpio.c.

References GPIO_DIR_IN, GPIO_DIR_IN_STR, GPIO_DIR_OUT, and GPIO_DIR_OUT_STR.

Referenced by main(), and sysfsSetDirection().

{
  int         fd;
  char        buf[MAX_PATH]; 
  const char *sDir;

  switch( dir )
  {
    case GPIO_DIR_IN:
      sDir = GPIO_DIR_IN_STR;
      break;
    case GPIO_DIR_OUT:
      sDir = GPIO_DIR_OUT_STR;
      break;
    default:
      LOGERROR("GPIO %d: \"%s\": Invalid direction. Must be one of: %d %d.",
        gpio, dir, GPIO_DIR_IN, GPIO_DIR_OUT);
      return RC_ERROR;
  }

  sprintf(buf, "%s/gpio%d/direction", GpioRoot, gpio);

  if( (fd = open(buf, O_WRONLY)) < 0 )
  {
    LOGSYSERROR("open(\"%s\", O_WRONLY)", buf);
    return RC_ERROR;
  }

  if( write(fd, sDir, strlen(sDir)) < 0 )
  {
    LOGSYSERROR("write(%d, \"%s\", %zu)", fd, sDir, strlen(sDir));
    close(fd);
    return RC_ERROR;
  }

  close(fd);

  LOGDIAG3("GPIO %d direction set to %s.", gpio, sDir);

  return OK;
}

int gpioSetEdge	(	int	gpio,
		int	edge
	)

Set GPIO edge trigger type.

Method: sysfs

Parameters

gpio	The sysfs exported GPIO number.
edge	Edge. One of: GPIO_EDGE_NONE(0) GPIO_EDGE_RISING(1) GPIO_EDGE_FALLING(2) GPIO_EDGE_BOTH(3)

Returns

On success OK(0) is returned, otherwise RC_ERROR(-1) is returned.

Definition at line 292 of file gpio.c.

References GPIO_EDGE_BOTH, GPIO_EDGE_BOTH_STR, GPIO_EDGE_FALLING, GPIO_EDGE_FALLING_STR, GPIO_EDGE_NONE, GPIO_EDGE_NONE_STR, GPIO_EDGE_RISING, and GPIO_EDGE_RISING_STR.

Referenced by main().

{
  int         fd;
  char        buf[MAX_PATH]; 
  const char *sEdge;

  switch( edge )
  {
    case GPIO_EDGE_NONE:
      sEdge = GPIO_EDGE_NONE_STR;
      break;
    case GPIO_EDGE_RISING:
      sEdge = GPIO_EDGE_RISING_STR;
      break;
    case GPIO_EDGE_FALLING:
      sEdge = GPIO_EDGE_FALLING_STR;
      break;
    case GPIO_EDGE_BOTH:
      sEdge = GPIO_EDGE_BOTH_STR;
      break;
    default:
      LOGERROR("GPIO %d: \"%s\": Invalid edge. Must be in range [%d-%d].",
        gpio, edge, GPIO_EDGE_NONE, GPIO_EDGE_BOTH);
      return RC_ERROR;
  }

  sprintf(buf, "%s/gpio%d/edge", GpioRoot, gpio);

  if( (fd = open(buf, O_WRONLY)) < 0 )
  {
    LOGSYSERROR("open(\"%s\", O_WRONLY)", buf);
    return RC_ERROR;
  }

  if( write(fd, sEdge, strlen(sEdge)) < 0 )
  {
    LOGSYSERROR("write(%d, \"%s\", %zu)", fd, sEdge, strlen(sEdge));
    close(fd);
    return RC_ERROR;
  }

  close(fd);

  LOGDIAG3("GPIO %d edge set to %s.", gpio, sEdge);

  return OK;
}

int gpioSetPull	(	int	gpio,
		int	pull
	)

Set GPIO pull.

Methodsys mmap

Parameters

gpio	The sysfs exported GPIO number.
pull	Pull type. One of: GPIO_PULL_DS(0) to disabled GPIO_PULL_UP(1) to pull-up GPIO_PULL_DN(2) to pull-down

Returns

On success OK(0) is returned, otherwise RC_ERROR(-1) is returned.

Definition at line 340 of file gpio.c.

{
  LOGERROR("Sysfs GPIO pull operation not supported.");
  return RC_ERROR;
}

int gpioUnexport

(

int

gpio

)

Unexport (delete) a GPIO interface.

The call requires root privaleges.

Method: sysfs

Parameters

gpio	The sysfs exported GPIO number.

Returns

On success OK(0) is returned, otherwise RC_ERROR(-1) is returned.

Definition at line 221 of file gpio.c.

Referenced by main().

{
  int   fd;
  char  buf[MAX_PATH]; 

  sprintf(buf, "%s/unexport", GpioRoot);

  if( (fd = open(buf, O_WRONLY)) < 0 )
  {
    LOGSYSERROR("open(\"%s\", O_WRONLY)", buf);
    return RC_ERROR;
  }

  sprintf(buf, "%d", gpio); 

  if( write(fd, buf, strlen(buf)) < 0 )
  {
    LOGSYSERROR("write(%d, \"%s\", %zu)", fd, buf, strlen(buf));
    close(fd);
    return RC_ERROR;
  }

  close(fd);

  LOGDIAG3("Unexported GPIO %d interface.", gpio);

  return OK;
}

int gpioWrite	(	int	gpio,
		int	value
	)

Write GPIO value.

Method: sysfs

Parameters

gpio	The sysfs exported GPIO number.
value	GPIO pin value. One of: 0 (low) or 1 (high).

Returns

On success OK(0) is returned, otherwise RC_ERROR(-1) is returned.

Definition at line 414 of file gpio.c.

Referenced by sysfsWrite().

{
  int   fd;
  char  buf[MAX_PATH]; 
  char  c;

  sprintf(buf, "%s/gpio%d/value", GpioRoot, gpio);

  if( (fd = open(buf, O_WRONLY)) < 0 )
  {
    LOGSYSERROR("open(\"%s\", O_WRONLY)", buf);
    return RC_ERROR;
  }

  c = value == 0? '0': '1';

  if( write(fd, &c, 1) < 0 )
  {
    LOGSYSERROR("write(%s, \"%c\", 1)", fd, c);
    close(fd);
    return RC_ERROR;
  }

  LOGDIAG3("Wrote GPIO %d value %c.", gpio, c);

  return OK;
}