z2-gpio.c

/* This seems to work if run with "picoc mainprog.c z2-gpio.c"               */
/* It does not run if mainprog.c is listed after z2-gpio.c.          */
/* And the main function must be defined as below (or with no args). */
/* int main(int argc, char ** argv)                                  */

/*
 * GPIO user space helpers
 *
 * Copyright 2009 Analog Devices Inc.
 * Michael Hennerich (hennerich@blackfin.uclinux.org)
 *
 * Licensed under the GPL-2 or later
 */

#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <unistd.h>

#define GPIO_DIR_IN 0
#define GPIO_DIR_OUT    1

int gpio_export(unsigned gpio)
{
    FILE *fp = fopen("/sys/class/gpio/export", "w");
    if (fp == NULL) {
        perror("gpio/export");
        return -1;
    }
    fprintf(fp, "%i", gpio);
    fclose(fp);
    return 0;
}

int gpio_unexport(unsigned gpio)
{
    FILE *fp = fopen("/sys/class/gpio/export", "w");
    if (fp == NULL) {
        perror("gpio/unexport");
        return -1;
    }
    fprintf(fp, "%i", gpio);
    fclose(fp);
    return 0;
}

int gpio_dir(unsigned gpio, unsigned dir)
{
    FILE *fp;
    char buf[60];

    snprintf(buf, sizeof(buf), "/sys/class/gpio/gpio%d/direction", gpio);
    fp = fopen(buf, "w");
    if (fp == NULL) {
        perror("gpio/direction");
        return -1;
    }

    if (dir == GPIO_DIR_OUT)
        fprintf(fp, "out");
    else
        fprintf(fp, "in");

    fclose(fp);
    return 0;
}

int gpio_dir_out(unsigned gpio)
{
    return gpio_dir(gpio, GPIO_DIR_OUT);
}

int gpio_dir_in(unsigned gpio)
{
    return gpio_dir(gpio, GPIO_DIR_IN);
}

int set_gpio_value(unsigned gpio, unsigned value)
{
    FILE *fp;
    char buf[60];

    snprintf(buf, sizeof(buf), "/sys/class/gpio/gpio%d/value", gpio);

    fp = fopen(buf, "w");
    if (fp == NULL) {
        perror("gpio/value");
        return -1;
    }

    if (value)
        fprintf(fp, "1");
    else
        fprintf(fp, "0");

    fclose(fp);
    return 0;
}

int get_gpio_value(unsigned gpio)
{
    FILE *fp;
    int value = 0;
    char buf[60];

    snprintf(buf, sizeof(buf), "/sys/class/gpio/gpio%d/value", gpio);

    fp = fopen(buf, "r");
    if (fp == NULL) {
        perror("gpio/value");
        return -1;
    }

    fscanf(fp, "%d", &value);

    fclose(fp);
    return value;
}