pi_gpio.c

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#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <unistd.h>
#include <inttypes.h>
#include <fcntl.h>
#include <errno.h>
#include <poll.h>
#include <pthread.h>

#include "pihwm.h"
#include "pi_gpio.h"

static pthread_t isr_handler_thread;
static int isr_handler_flag;

typedef struct
{
    int pin;
    void (*isr) (int);
} isr_t;


static int
gpio_edge (int pin, char *edge)
{
    FILE *file;
    char filename[35];

    sprintf(filename, "/sys/class/gpio/gpio%d/edge", pin);
    file = fopen(filename, "w");
    if ( file == NULL )
    {
        debug("[%s] Can't open file (edge): %s\n", __func__, filename);
        return -1;
    }

    fwrite(edge, sizeof (char), strlen (edge) + 1, file);

    fclose(file);

    return 1;
}

static int
gpio_valfd (int pin)
{
    int file;
    char filename[35];

    sprintf(filename, "/sys/class/gpio/gpio%d/value", pin);
    file = open(filename, O_RDWR | O_NONBLOCK);
    if ( file < 0 )
    {
        debug("[%s] Can't open file (value): %s\n", __func__, filename);
        return -1;
    }
    else
    {
        return file;
    }

}

int
gpio_init (unsigned int pin, unsigned int dir)
{
    FILE *file;
    char filename[35], pinStr[2];

    gpio_release(pin);

    file = fopen("/sys/class/gpio/export", "w");
    if ( file == NULL )
    {
        debug("[%s] Can't open file (export)\n", __func__);
        return -1;
    }

    sprintf(pinStr, "%d", pin);
    /* TODO: Add check here */
    fwrite(pinStr, sizeof (char), strlen (pinStr), file);

    fclose(file);

    sprintf(filename, "/sys/class/gpio/gpio%d/direction", pin);
    file = fopen(filename, "w");
    if ( file == NULL )
    {
        debug("[%s] Can't open file (direction)\n", __func__);
        return -1;
    }

  int ret = 1;
    if ( dir == 0 )
    {
        fwrite("out", sizeof (char), 3, file);
    } 
    else if ( dir == 1 )
    {
        fwrite("in", sizeof (char), 2, file);
    } 
    else
    {
        debug("[%s] Can't set pin direction.\n", __func__);
    ret = -1;
    }

    fclose(file);

    return ret;
}


static void *
isr_handler (void *isr)
{
    struct pollfd fdset[2];
    int nfds = 2, gpio_fd, rc;
    char *buf[64];

    isr_t i = *(isr_t *) isr;

    if ( isr_handler_flag )
    {
        printf("isr_handler running\n");

        /* Get /value fd
        TODO: Add check here */
        gpio_fd = gpio_valfd((int) i.pin);


        while ( 1 )
        {
            memset((void *) fdset, 0, sizeof (fdset));

            fdset[0].fd = STDIN_FILENO;
            fdset[0].events = POLLIN;

            fdset[1].fd = gpio_fd;
            fdset[1].events = POLLPRI;

            rc = poll(fdset, nfds, 1000);   /* Timeout in ms */

            if ( rc < 0 )
            {
                debug("\npoll() failed!\n");
                return (void *) -1;
            }

            if ( rc == 0 )
            {
                debug("poll() timeout.\n");
                if ( isr_handler_flag == 0 )
                {
                    debug("exiting isr_handler (timeout)");
                    pthread_exit(NULL);
                }
            }

            if ( fdset[1].revents & POLLPRI )
            {
                /* We have an interrupt! */
                if ( -1 == read(fdset[1].fd, buf, 64) )
                {
                    debug("read failed for interrupt");
                    return (void *) -1;
                }

                (*i.isr) (i.pin);       /* Call the ISR */
            }

            if ( fdset[0].revents & POLLIN )
            {
                if ( -1 == read(fdset[0].fd, buf, 1) )
                {
                    debug("read failed for stdin read");
                    return (void *) -1;
                }

                printf("\npoll() stdin read 0x%2.2X\n", (unsigned int) buf[0]);
            }

            fflush(stdout);
        }
    }
    else
    {
        debug("exiting isr_handler (flag)");
        pthread_exit(NULL);
    }

}

int
gpio_set_int (unsigned int pin, void (*isr) (int), char *mode)
{
    /* Details of the ISR */
    isr_t *i = (isr_t *) malloc(sizeof (isr_t));
    i->pin = pin;
    i->isr = isr;

    /* Set up interrupt */
    gpio_edge(pin, mode);

    /* Set isr_handler flag and create thread
    TODO: check for errors using retval */
    isr_handler_flag = 1;
    pthread_create(&isr_handler_thread, NULL, isr_handler, (void *) i);
    pthread_tryjoin_np(isr_handler_thread, NULL);

    return 1;
}

int
gpio_clear_int (unsigned int pin)
{
    /* this will terminate isr_handler thread */
    isr_handler_flag = 0;

    /* TODO: Reset "edge", release pin? */
    return  0;          /* Is this a correct return result. */
}

int
gpio_write (unsigned int pin, unsigned int val)
{
    int file;
  int ret = 1;

    file = gpio_valfd (pin);

    if ( val == 0 )
    {
        if ( write(file, "0", (sizeof(char) * 1)) == -1 )
        {
            debug("[%s] Can't write to GPIO pin", __func__);
      ret = -1;
        }
    } 
    else if ( val == 1 )
    {
        if ( write(file, "1", (sizeof(char) * 1)) == -1 )
        {
            debug("[%s] Can't write to GPIO pin", __func__);
      ret = -1;
        }
    } 
    else 
    {
        debug("[%s] Wrong value for the GPIO pin", __func__);
    ret = -1;
    }

    close(file);

    return ret;
}

int
gpio_read (unsigned int pin)
{
  char valStr[1] = "";
  unsigned int val;
  int file;

  file = gpio_valfd (pin);
  /* fseek(file, 0, SEEK_SET); */
  if (read (file, &valStr, 1) == 1)
    {
      val = atoi (valStr);
      debug ("[%s] valStr: %s, val: %d\n", __func__, valStr, val);
    }
  else
    {
      debug ("[%s] Can't read pin value", __func__);
      val = -1;
    }

  close (file);
  return val;
}

int
gpio_release (unsigned int pin)
{
    FILE *file;
    char pinStr[3];

    file = fopen("/sys/class/gpio/unexport", "w");
    if ( file == NULL )
    {
        debug("[%s] Can't open file (unexport)\n", __func__);
        return -1;
    }

    sprintf(pinStr, "%d", pin);
    fwrite(pinStr, sizeof (char), strlen (pinStr), file);

    fclose(file);

    return 1;
}