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  Home >  Support > TI Series > MYD-AM335X
 
ARM Linux GPIO sample code
 
Question
Please download the sample code package from below link: http://www.myirtech.com/download/code/gpio.tar.gz (include source code, Makefile and image which is compiled using arm-none-linux-gnueabi-gcc)
Answer

Source code


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/********************************************************************
*                 copyright (C) 2014 all rights reserved
*                         @file: gpio.c
*                   @Created: 2014-8-6 15:00
*                      @Author: conway chen
*           @Description: test gpios interrupt
*          @Modify Date: 2014-8-6 15:00
*********************************************************************/
#include<stdio.h>
#include <stdlib.h>
#include<sys/types.h>
#include<sys/stat.h>
#include<fcntl.h>
#include<unistd.h>
#include<errno.h>
#include<string.h>
#include <poll.h>
 
#define SYSFS_GPIO_DIR "/sys/class/gpio"
#define GPIO_LED 41
#define MAX_BUF 60
#define POLL_TIMEOUT (3 * 1000) /* 3 seconds */
#define OUT 1
#define IN 0
 
/**
 * brief: export the GPIO to user space
 * @Param: gpio: the GPIO number
 */
int gpio_export(unsigned int gpio)
{
        int fd ,len;
        char buf[MAX_BUF];
 
        fd = open(SYSFS_GPIO_DIR "/export" ,O_WRONLY);
        if (fd < 0) {
                perror("gpio/export");
                return fd;
        }
        len = snprintf(buf ,sizeof(buf) ,"%d" ,gpio);
        write(fd ,buf ,len);
        close(fd);
        return 0;
}
 
/**
 * brief: unexport the GPIO to user space
 * @Param: gpio: the GPIO number
 */ 
int gpio_unexport(unsigned int gpio)
{
        int fd ,len;
        char buf[MAX_BUF];
 
        fd = open(SYSFS_GPIO_DIR "/unexport" ,O_WRONLY);
        if (fd < 0) {
                perror("gpio/unexport");
                return fd;
        }
        len = snprintf(buf ,sizeof(buf) ,"%d" ,gpio);
        write(fd ,buf ,len);
        close(fd);
        return 0;
}
 
/**
 * brief: configure GPIO for input or output
 * @Param: gpio: the GPIO number
 * @Param: out_flag: the flag of output or input.It's value can be 1 or 0. 
 */
int gpio_set_dir(unsigned int gpio ,int out_flag)
{
        int fd ,len;
        char buf[MAX_BUF];
 
        len = snprintf(buf, sizeof(buf), SYSFS_GPIO_DIR "/gpio%d/direction", gpio);
        fd = open(buf ,O_WRONLY);
        if (fd < 0) {
                perror(buf);
                return fd;
        }
        if (out_flag)
                write(fd ,"out" ,4);
        else
                write(fd ,"in" ,3);
        close(fd);
        return 0;
}
 
/**
 * brief: Set the value of GPIO
 * @Param: gpio: the GPIO number
 * @Param: value: the value of GPIO. Supports values of 0 and 1.
 */ 
int gpio_set_value(unsigned int gpio, unsigned int value) 
    int fd, len; 
    char buf[MAX_BUF]; 
    
    len = snprintf(buf, sizeof(buf), SYSFS_GPIO_DIR "/gpio%d/value", gpio);     
    fd = open(buf, O_WRONLY);
        if (fd < 0) { 
        perror("gpio/set-value"); 
        return fd; 
    
    
    if (value) 
        write(fd, "1", 2); 
    else 
        write(fd, "0", 2); 
    
    close(fd); 
    return 0; 
}
 
/**
 * brief: get the value of GPIO
 * @Param: gpio: the GPIO number
 * @Param: value: pointer to the value of GPIO
 */
int gpio_get_value(unsigned int gpio, unsigned int *value)
{
        int fd, len;
        char ch;
        char buf[MAX_BUF];
 
        len = snprintf(buf ,sizeof(buf), SYSFS_GPIO_DIR "/gpio%d/value" ,gpio);
        fd = open(buf ,O_RDONLY);
        if (fd < 0) {
                perror("gpio_get_value");
                return fd;
        }
        read(fd ,&ch ,1);
        if (ch == '1')
                *value = 1;
        else if(ch == '0')
                        *value = 0;
        close(fd);
        return 0;
}
 
/**
 * brief: set the edge that trigger interrupt
 * @Param: gpio: the GPIO number
 * @Param: edge:  edge that trigger interrupt
 */
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) {
                perror("gpio_set_edge");
                return fd;
        }
        write(fd ,edge ,strlen(edge) + 1);
        close(fd);
        return 0;
}
 
/**
 * brief: open gpio device and return the file descriptor
 * @Param: gpio: the GPIO number
 */ 
int gpio_fd_open(unsigned int gpio) 
    int fd, len; 
    char buf[MAX_BUF]; 
   
    len = snprintf(buf, sizeof(buf), SYSFS_GPIO_DIR "/gpio%d/value", gpio); 
    
    fd = open(buf, O_RDONLY | O_NONBLOCK ); 
    if (fd < 0) { 
        perror("gpio/fd_open"); 
    
    return fd; 
   
/**
 * brief: close gpio device
 * @Param: fd: the file descriptor of gpio
 */
int gpio_fd_close(int fd) 
    return close(fd); 
   
/**
 * @brief: main function
 * @Param: argc: number of parameters
 * @Param: argv: parameters list
 */ 
int main(int argc, char **argv) 
    struct pollfd *fdset; 
    int nfds = 1; 
    int gpio_fd, timeout, rc; 
    char *buf[MAX_BUF]; 
    unsigned int gpio; 
    int len;
    char *cmd;
    unsigned int value;
       
          fdset = (struct pollfd*)malloc(sizeof(struct pollfd)); 
   
    if (argc < 3) { 
        printf("Usage: %s <gpio-pin> <direction> [value]\n\n", argv[0]);       
        exit(-1); 
    }
    cmd = argv[2];
    gpio = atoi(argv[1]);
        gpio_export(gpio);
         
    if (strcmp(cmd, "interrupt") == 0) {
            printf("\n**************************GPIO interrupt***************************\n");
                   
                gpio_set_dir(gpio, IN); 
                gpio_set_edge(gpio, "rising"); 
                gpio_fd = gpio_fd_open(gpio);
                 
                /* GPIO_LED configure */
                //gpio_export(GPIO_LED); 
                //gpio_set_dir(GPIO_LED, OUT);
                 
                timeout = POLL_TIMEOUT; 
            
                while (1) { 
                    memset((void*)fdset, 0, sizeof(fdset));