Linux应用编程 - sysfs方式操作GPIO

简介：

应用层想要对底层硬件进行操控，通常可以通过两种方式

通常情况下，简单地设备会使用 sysfs 方式操控，如 LED、GPIO 等。较复杂的设备通常会使用设备节点的方式，如 LCD、触摸屏、摄像头等。

首先，配置内核启用sysfs GPIO支持

CONFIG_GPIO_SYSFS=y

一、命令操作GPIO

以GPIO1_IO03为例，对应gpio编号为3

1、GPIO输出

$ echo 3 > /sys/class/gpio/export //导出编号为3的GPIO，生成gpio3
$ echo out > /sys/class/gpio/gpio3/direction //设置输出 out：输出 in：输入
$ echo 1 > /sys/class/gpio/gpio3/value //输出高电平 1：高电平 0：低电平
$ echo 3 > /sys/class/gpio/unexport //删除导出的编号为3的GPIO

2、GPIO输入

配置输入前也要导出gpio，不再赘述

$ echo in > /sys/class/gpio/gpio3/direction //设置输出 out：输出 in：输入

$ cat /sys/class/gpio/gpio3/value //查看输入电平

二、代码操作GPIO

1、设置gpio输出

/*
*****************************************************************************************
*	函 数 名: sysfs_gpio_set
*	功能说明: 设置gpio电平状态
*	形    参: u32GpioNum : gpio编号
*             u32Value   : 1:高电平，0:低电平
*	返 回 值: 0:成功,-1:失败
*****************************************************************************************
*/
s32 sysfs_gpio_set(u32 u32GpioNum, u32 u32Value)
{u8 u8Buf[2]     ={0,};u8 u8Fname[128] = {0,};FILE *fp        = NULL;/* 1.引脚导出, 类似于：echo 3 > /sys/class/gpio/export */sprintf((char *)u8Fname, "/sys/class/gpio/export");    if (NULL == (fp = fopen((char *)u8Fname, "w"))){LOG_ERR("Cannot open %s.\n", u8Fname);return -1;}fprintf(fp, "%d", u32GpioNum);              //gpio编号写入 fp文件fclose(fp);/* 2.设置方向,类似于：echo out > /sys/class/gpio/gpio3/direction */memset(u8Fname, 0x0, sizeof(u8)*128);sprintf(u8Fname, "/sys/class/gpio/gpio%d/direction", u32GpioNum);if (NULL == (fp = fopen(u8Fname, "rb+"))){LOG_ERR("Cannot open %s.\n", u8Fname);return -1;}fprintf(fp, "out");                         //设置方向，"out"写入 fpfclose(fp);/* 3.设置gpio输出电平,类似于：echo 1 > /sys/class/gpio/gpio3/value */memset(u8Fname, 0x0, sizeof(u8)*128);sprintf((char *)u8Fname, "/sys/class/gpio/gpio%d/value", u32GpioNum);if (NULL == (fp=fopen((char *)u8Fname, "rb+"))){LOG_ERR("Cannot open %s.\n", u8Fname);return -1;}u8Buf[0] = u32Value + 0x30;                         //把数字转为ASCII码fwrite(u8Buf, sizeof(u8), sizeof(u8Buf)-1, fp);     //写入gpio电平,fclose(fp);/* 4.取消导出, 类似于：echo 3 > /sys/class/gpio/unexport */sprintf((char *)u8Fname, "/sys/class/gpio/unexport");if (NULL == (fp = fopen((char *)u8Fname, "w"))){LOG_ERR("Cannot open %s.\n", u8Fname);return -1;}fprintf(fp, "%d", u32GpioNum);fclose(fp);return 0;
}

2、获取gpio输入电平状态

/*
*****************************************************************************************
*	函 数 名: sysfs_gpio_get
*	功能说明: 获取gpio电平状态
*	形    参: u32GpioNum : gpio编号
*	返 回 值: 返回1:高电平,返回0:低电平
*****************************************************************************************
*/
s32 sysfs_gpio_get(u32 u32GpioNum)
{u8 u8Buf[8] = {0};u8 u8Fname[128] = {0,};FILE *fp        = NULL;/* 1.引脚导出, 等价于：echo 3 > /sys/class/gpio/export */sprintf((char *)u8Fname, "/sys/class/gpio/export");if (NULL == (fp = fopen((char *)u8Fname, "w"))){LOG_ERR("Cannot open %s.\n", u8Fname);return -1;}fprintf(fp, "%d", u32GpioNum);                  //gpio编号写入 fp文件fclose(fp);/* 2.设置方向,等价于：echo in > /sys/class/gpio/gpio3/direction */memset(u8Fname, 0x0, sizeof(u8)*128);sprintf(u8Fname, "/sys/class/gpio/gpio%d/direction", u32GpioNum);if (NULL == (fp = fopen(u8Fname, "rb+"))){LOG_ERR("Cannot open %s.\n", u8Fname);return -1;}fprintf(fp, "in");                              //设置方向，"in"写入 fpfclose(fp);/* 3.获取gpio电平,类似于：cat /sys/class/gpio/gpio3/value */memset(u8Fname, 0x0, sizeof(u8)*128);sprintf((char *)u8Fname, "/sys/class/gpio/gpio%d/value", u32GpioNum);if (NULL == (fp=fopen((char *)u8Fname, "rb+"))){LOG_ERR("Cannot open %s.\n", u8Fname);return -1;}fread(u8Buf, sizeof(u8), sizeof(u8), fp);       //读到 gpio电平, 字符串格式fclose(fp);/* 4.取消导出, 等价于：echo 3 > /sys/class/gpio/unexport */sprintf((char *)u8Fname, "/sys/class/gpio/unexport");if (NULL == (fp = fopen((char *)u8Fname, "w"))){LOG_ERR("Cannot open %s.\n", u8Fname);return -1;}fprintf(fp, "%d", u32GpioNum);fclose(fp);return atoi((char *)u8Buf);         //返回gpio电平
}

3、应用代码测试

#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <string.h>
#include "hal.h"
#include "hal_gpio.h"/* LED  GPIO1_IO03 gpionum = (1 - 1) * 32 + 3 = 3  */
int main(int argc, char* argv[])
{int i;u32 u32Gpio, u32Io, u32GpioNum;/* GPIO1_IO03 转换num */u32Gpio = 1;u32Io = 3;u32GpioNum = (u32Gpio - 1) * 32 + u32Io;if (argc != 2 || !strcmp(argv[1], "--help") || !strcmp(argv[1], "-h")) {printf("Usage: %s""0 : off\n""1 : on\n""2 : flip\n""\n", argv[0]);return -1;}switch((int)argv[1]) {case 0:sysfs_gpio_set(u32GpioNum, 0);break;case 1: sysfs_gpio_set(u32GpioNum, 1);break;case 2:for (i = 0; i < 3; i++) {sysfs_gpio_set(u32GpioNum, 1);sleep(1);sysfs_gpio_set(u32GpioNum, 0);sleep(1);}break;default:return -1;}return 0;
}

测试结果：