gpio.c

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#include "gpio.h"

int gpio_unexport(int num) {
    // open gpio value file
    int fd = open(GPIO_PATH "unexport", O_WRONLY);
    if (fd < 0) {
        rl_log(ERROR, "could not open GPIO unexport file");
        return FAILURE;
    }

    // export gpio
    char buf[5] = "";
    int len = snprintf(buf, sizeof(buf), "%d", num);
    write(fd, buf, len);

    // close file
    close(fd);

    return SUCCESS;
}

int gpio_export(int num) {
    // open gpio value file
    int fd = open(GPIO_PATH "export", O_WRONLY);
    if (fd < 0) {
        rl_log(ERROR, "could not open GPIO export file");
        return FAILURE;
    }

    // export gpio
    char buf[5] = "";
    int len = snprintf(buf, sizeof(buf), "%d", num);
    write(fd, buf, len);

    // close file
    close(fd);

    return SUCCESS;
}

int gpio_dir(int num, rl_direction dir) {

    // open gpio direction file
    char file_name[MAX_PATH_LENGTH];
    sprintf(file_name, GPIO_PATH "gpio%d/direction", num);
    int fd = open(file_name, O_WRONLY);
    if (fd < 0) {
        rl_log(ERROR, "could not open GPIO direction file");
        return FAILURE;
    }

    // set direction
    if (dir == OUT) {
        write(fd, "out", 4);
    } else {
        write(fd, "in", 3);
    }
    // close file
    close(fd);

    return SUCCESS;
}

int gpio_interrupt(int num, rl_edge edge) {

    // open gpio edge file
    char file_name[MAX_PATH_LENGTH];
    sprintf(file_name, GPIO_PATH "gpio%d/edge", num);
    int fd = open(file_name, O_WRONLY);
    if (fd < 0) {
        rl_log(ERROR, "could not open GPIO edge file");
        return FAILURE;
    }

    // set edge
    switch (edge) {
    case NONE:
        write(fd, "none", 5);
        break;
    case RISING:
        write(fd, "rising", 7);
        break;
    case FALLING:
        write(fd, "falling", 8);
        break;
    case BOTH:
        write(fd, "both", 5);
        break;
    }

    // close file
    close(fd);

    return SUCCESS;
}

int gpio_set_value(int num, int val) {

    // open gpio value file
    char file_name[MAX_PATH_LENGTH];
    sprintf(file_name, GPIO_PATH "gpio%d/value", num);
    int fd = open(file_name, O_WRONLY);
    if (fd < 0) {
        rl_log(ERROR, "could not open GPIO value file");
        return FAILURE;
    }

    // set value
    if (val == 0) {
        write(fd, "0", 2);
    } else {
        write(fd, "1", 2);
    }

    // close file
    close(fd);

    return SUCCESS;
}

int gpio_get_value(int num) {

    // open gpio value file
    char file_name[MAX_PATH_LENGTH];
    sprintf(file_name, GPIO_PATH "gpio%d/value", num);
    int fd = open(file_name, O_RDONLY);
    if (fd < 0) {
        rl_log(ERROR, "could not open GPIO value file");
        return FAILURE;
    }

    // read value
    char buf[2] = "";
    read(fd, &buf, 1);

    // close file
    close(fd);

    return atoi(buf);
}

int gpio_wait_interrupt(int num, int timeout) {

    // open gpio value file
    char file_name[MAX_PATH_LENGTH];
    sprintf(file_name, GPIO_PATH "gpio%d/value", num);
    int fd = open(file_name, O_RDONLY);
    if (fd < 0) {
        rl_log(ERROR, "could not open GPIO value file");
        return FAILURE;
    }

    // set up polling struct
    struct pollfd fds;
    fds.fd = fd;
    fds.events = POLLPRI;
    int nfds = 1;
    int ret;

    // dummy read (enables blocking polling)
    char buf[2] = "";
    read(fds.fd, &buf, 1);

    // wait on gpio change
    ret = poll(&fds, nfds, timeout);
    if (ret < 0) {
        rl_log(ERROR, "GPIO poll failed");
        return FAILURE;
    }

    // wait for signal to settle
    usleep(MIN_BUTTON_TIME);

    // read value
    lseek(fds.fd, 0, SEEK_SET);
    read(fds.fd, &buf, 1);

    close(fd);

    return atoi(buf);
}