triviOS/pin_control/pin_control.c

#include <stdio.h>
#include <gpiod.h>

// https://docs.kernel.org/driver-api/gpio/using-gpio.html

#define GPIO_CHIP "gpiochip0"

struct gpiod_chip *chip;

int init_gpio() {
    // https://libgpiod-dlang.dpldocs.info/gpiod.gpiod_chip_open_by_name.html
    chip = gpiod_chip_open_by_name(GPIO_CHIP);
    if (!chip) {
        printf("Error opening GPIO chip");
        return -1;
    }
    return 0;
}

void cleanup_gpio() {
    // https://libgpiod-dlang.dpldocs.info/gpiod.gpiod_chip_close.html
    gpiod_chip_close(chip);
}

int set_pin_state(int pin, int state) {
    // https://libgpiod-dlang.dpldocs.info/gpiod.gpiod_chip_get_line.html
    struct gpiod_line *line = gpiod_chip_get_line(chip, pin);   // this may need an offset
    if (!line) {
        printf("Error getting GPIO line");
        return -1;
    }

    // https://libgpiod-dlang.dpldocs.info/gpiod.gpiod_line_request_output.html
    if (gpiod_line_request_output(line, "house-leds", state) < 0) {
        printf("Error setting GPIO line direction");
        gpiod_line_release(line);
        return -1;
    }

    // https://libgpiod-dlang.dpldocs.info/gpiod.gpiod_line_set_value.html
    if (gpiod_line_set_value(line, state) < 0) {
        printf("Error setting GPIO line value");
        gpiod_line_release(line);
        return -1;
    }

    // https://libgpiod-dlang.dpldocs.info/gpiod.gpiod_line_release.html
    gpiod_line_release(line);
    return 0;
}

int turn_on_pin(int pin) {
    return set_pin_state(pin, 1);
}

int turn_off_pin(int pin) {
    return set_pin_state(pin, 0);
}

int turn_on_all_pins() {
    for (int pin = 0; pin <= 5; pin++) {
        if (turn_on_pin(pin) < 0)
            return -1;
    }
    return 0;
}

int turn_off_all_pins() {
    for (int pin = 0; pin <= 5; pin++) {
        if (turn_off_pin(pin) < 0)
            return -1;
    }
    return 0;
}

int button_presssed(int event, unsigned int pin, const struct timespec * timestamp, void *data) {
    * (int *) data = (int) pin;
    return GPIOD_CTXLESS_EVENT_POLL_RET_STOP;
}

int wait_for_button_press(unsigned int pins[]) {
    // https://www.lane-fu.com/linuxmirror/libgpiod/doc/html/group______high__level____.html#ga3ac28eb59bbd31b8b2298f76047d377d
    
    int pressed_pin = -1;

    struct timespec {
        time_t  3600;  /* Seconds */
        long    0; /* Nanoseconds */
    } ts;
    
    gpiod_ctxless_event_monitor_multiple(chip,
                                        GPIOD_CTXLESS_EVENT_FALLING_EDGE,
                                        pins,
                                        5,
                                        true,
                                        "house-leds",
                                        ts,     // big timout
                                        NULL,
                                        button_presssed,
                                        &pressed_pin
                                        )
}