This document mainly introduces how to use GPIO interrupts on Khadas SBC. You will know how to use GPIO interrupts with the GPIO number test program.

Connect the physical pins PIN20 and PIN15 using a DuPont line.

Get GPIOH_6 number

Refer 40-Pin Header to get the GPIO number is 433.

Export GPIO

$ echo 433 | sudo tee /sys/class/gpio/export

Get demo source code

gpio_interrupts.c

// SPDX-License-Identifier: (GPL-2.0+ OR MIT)
/*
 * Copyright (c) 2022 Wesion Technology Co., Ltd.
 *
 * Author: Yan <yan-wyb@foxmail.com> 
 *
 */
 
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <fcntl.h>
#include <errno.h>
#include <poll.h>
 
#define SYSFS_GPIO_DIR  "/sys/class/gpio"
#define MAX_BUF     255
 
int gpio_export(unsigned int gpio){
 
    int fd, len;
    char buf[MAX_BUF];
 
    fd = open(SYSFS_GPIO_DIR "/export", O_WRONLY);
 
    if (fd < 0) {
        fprintf(stderr, "Can't export GPIO %d pin: %s\n", gpio, strerror(errno));
        return fd;
    }
 
    len = snprintf(buf, sizeof(buf), "%d", gpio);
    write(fd, buf, len);
    close(fd);
 
    return 0;
}
 
int gpio_unexport(unsigned int gpio){
 
    int fd, len;
    char buf[MAX_BUF];
 
    fd = open(SYSFS_GPIO_DIR "/unexport", O_WRONLY);
 
    if (fd < 0) {
        fprintf(stderr, "Can't unexport GPIO %d pin: %s\n", gpio, strerror(errno));
        return fd;
    }
 
    len = snprintf(buf, sizeof(buf), "%d", gpio);
    write(fd, buf, len);
    close(fd);
 
    return 0;
}
 
int gpio_set_edge(unsigned int gpio, char *edge){
 
    int fd, len;
    char buf[MAX_BUF];
 
    len = snprintf(buf, sizeof(buf), SYSFS_GPIO_DIR "/gpio%d/edge", gpio);
 
    fd = open(buf, O_WRONLY);
 
    if (fd < 0) {
        fprintf(stderr, "Can't set GPIO %d pin edge: %s\n", gpio, strerror(errno));
        return fd;
    }
 
    write(fd, edge, strlen(edge)+1);
    close(fd);
 
    return 0;
}
 
int gpio_set_pull(unsigned int gpio, char *pull){
 
    int fd, len;
    char buf[MAX_BUF];
 
    len = snprintf(buf, sizeof(buf), SYSFS_GPIO_DIR "/gpio%d/pull", gpio);
 
    fd = open(buf, O_WRONLY);
 
    if (fd < 0) {
        fprintf(stderr, "Can't set GPIO %d pin pull: %s\n", gpio, strerror(errno));
        return fd;
    }
 
    write(fd, pull, strlen(pull)+1);
    close(fd);
 
    return 0;
}
 
int main(int argc, char *argv[])
{
    struct pollfd fdset[2];
    int fd, ret, gpio;
    char buf[MAX_BUF];
 
    if (argc < 3 || argc > 4)   {
        fprintf(stdout, "usage : sudo sysfs_irq_test <gpio> <edge> [pull]\n");
        fflush(stdout);
        return  -1;
    }
 
    gpio = atoi(argv[1]);
    if (gpio_export(gpio))  {
        fprintf(stdout, "error : export %d\n", gpio);
        fflush(stdout);
        return  -1;
    }
 
    if (gpio_set_edge(gpio, argv[2])) {
        fprintf(stdout, "error : edge %s\n", argv[2]);
        fflush(stdout);
        return  -1;
    }
 
    if (argv[3] && gpio_set_pull(gpio, argv[3])) {
        fprintf(stdout, "error : pull %s\n", argv[3]);
        fflush(stdout);
        return  -1;
    }
 
    snprintf(buf, sizeof(buf), SYSFS_GPIO_DIR "/gpio%d/value", gpio);
    fd = open(buf, O_RDWR);
    if (fd < 0)
        goto out;
 
    while (1) {
        memset(fdset, 0, sizeof(fdset));
        fdset[0].fd = STDIN_FILENO;
        fdset[0].events = POLLIN;
        fdset[1].fd = fd;
        fdset[1].events = POLLPRI;
        ret = poll(fdset, 2, 3*1000);
 
        if (ret < 0) {
            perror("poll");
            break;
        }
 
        fprintf(stderr, ".");
 
        if (fdset[1].revents & POLLPRI) {
            char c;
            (void)read (fd, &c, 1) ;
            lseek (fd, 0, SEEK_SET) ;
            fprintf(stderr, "\nGPIO %d interrupt occurred!\n", gpio);
        }
 
        if (fdset[0].revents & POLLIN)
            break;
 
        fflush(stdout);
    }
 
    close(fd);
out:
    if (gpio_unexport(gpio))    {
        fprintf(stdout, "error : unexport %d\n", gpio);
        fflush(stdout);
    }
 
    return 0;
 }

Compile the source code

$ gcc -o gpio_interrupts gpio_interrupts.c

The test code running format is as follows:

$ sudo ./gpio_interrupts <edge> [pull]

Run test:

$ sudo ./gpio_interrupts rising down
.
GPIO 433 interrupt occurred!
..
GPIO 433 interrupt occurred!
.
GPIO 433 interrupt occurred!
.
GPIO 433 interrupt occurred!