Linux下用文件IO的方式操作GPIO（/sys/class/gpio）

古城微笑少年丶 2022-03-09 01:58 183阅读 0赞

英文不错的，可以看看：[https://blog.csdn.net/ruanjianruanjianruan/article/details/47734397][https_blog.csdn.net_ruanjianruanjianruan_article_details_47734397]

# 先看： #

# [嵌入式linux下操作GPIO][linux_GPIO] #

在[嵌入式][Link 1]设备中对GPIO的操作是最基本的操作。一般的做法是写一个单独驱动程序，网上大多数的例子都是这样的。其实[Linux][]下面有一个通用的GPIO操作接口，那就是我要介绍的 “/sys/class/gpio” 方式。首先，看看系统中有没有“/sys/class/gpio”这个文件夹。如果没有请在编译内核的时候加入 Device Drivers-> GPIO Support-> /sys/class/gpio/… (sysfs interface)。/sys/class/gpio 的使用说明：

1、gpio\_operation 通过/sys/文件接口操作IO端口 GPIO到文件系统的映射，

2、控制GPIO的目录位于/sys/`class``/gpio`

`3、/sys/class/gpio/export文件用于通知系统需要导出控制的GPIO引脚编号`

`4、/sys/class/gpio/unexport 用于通知系统取消导出`

`5、/sys/class/gpio/gpiochipX目录保存系统中GPIO寄存器的信息，包括每个寄存器控制引脚的起始编号base，寄存器名称，引脚总数 导出一个引脚的操作步骤`

`6、首先计算此引脚编号，引脚编号 = 控制引脚的寄存器基数 + 控制引脚寄存器位数`

`7、向/sys/class/gpio/export写入此编号，比如12号引脚，echo 12 > /sys/class/gpio/export，命令成功后生成/sys/class/gpio/gpio12目录，如果没有出现相应的目录，说明此引脚不可导出：`

`8、direction文件，定义输入输入方向，可以通过下面命令定义为输出,``direction接受的参数：in, out, high, low。high/low同时设置方向为输出`

`9、value文件是端口的数值，为1或0.`

`下面在2440下进行一下测试：`

1.取得GPIO信息，在终端中敲入以下命令:

1.  $ cd /sys/class/gpio  
2.  $ for i in gpiochip\* ; do echo \`cat $i/label\`: \`cat $i/base\` ; done

终端中显示如下:

1.  GPIOA: 0  
2.  GPIOE: 128  
3.  GPIOF: 160  
4.  GPIOG: 192  
5.  GPIOH: 224  
6.  GPIOB: 32  
7.  GPIOC: 64  
8.  GPIOD: 96

这里有可能不同

![Center][]

查找数据手册：得到的是地址对应的GPIO号，例如这里的209c000就是对应gpio1

![Center 1][]

2.计算GPIO号码

例如我们把GPE11用来控制LED。GPE0的头是128，GPE11 就是128+11 = 139.于是我们将139写入export中：

$ echo 139 > /sys/class/gpio/export

ls 一下看看有没有 gpio139这个目录，

3.GPIO控制测试：

1.  $ echo out > /sys/class/gpio/gpio139/direction  
2.  $ echo 1 > /sys/class/gpio/gpio139/value  
3.  $ echo 0 > /sys/class/gpio/gpio139/value

这时[LED灯][LED]就会灭或亮

# 再看： #

转自：[http://blog.sina.com.cn/s/blog\_7880d3350102w2um.html][http_blog.sina.com.cn_s_blog_7880d3350102w2um.html]

通过sysfs方式控制GPIO，先访问/sys/class/gpio目录，向export文件写入GPIO编号，使得该GPIO的操作接口从内核空间暴露到用户空间，GPIO的操作接口包括direction和value等，direction控制GPIO方向，而value可控制GPIO输出或获得GPIO输入。文件IO方式操作GPIO，使用到了4个函数open、close、read、write。

首先，看看系统中有没有“/sys/class/gpio”这个文件夹。如果没有请在编译内核的时候加入   Device Drivers-> GPIO Support ->/sys/class/gpio/… (sysfs interface)。

/sys/class/gpio 的使用说明：

gpio\_operation 通过/sys/文件接口操作IO端口 GPIO到文件系统的映射

◇  控制GPIO的目录位于/sys/class/gpio

◇  /sys/class/gpio/export文件用于通知系统需要导出控制的GPIO引脚编号

◇  /sys/class/gpio/unexport 用于通知系统取消导出

◇  /sys/class/gpio/gpiochipX目录保存系统中GPIO寄存器的信息，包括每个寄存器控制引脚的起始编号base，寄存器名称，引脚总数 导出一个引脚的操作步骤

◇  首先计算此引脚编号，引脚编号 = 控制引脚的寄存器基数 + 控制引脚寄存器位数

◇  向/sys/class/gpio/export写入此编号，比如12号引脚，在shell中可以通过以下命令实现，命令成功后生成/sys/class/gpio/gpio12目录，如果没有出现相应的目录，说明此引脚不可导出

◇  direction文件，定义输入输入方向，可以通过下面命令定义为输出。direction接受的参数：in, out, high, low。high/low同时设置方向为输出，并将value设置为相应的1/0

◇  value文件是端口的数值，为1或0

几个例子：

1. 导出

/sys/class/gpio\# echo 44 > export

2. 设置方向

/sys/class/gpio/gpio44\# echo out > direction

3. 查看方向

/sys/class/gpio/gpio44\# cat direction

4. 设置输出

/sys/class/gpio/gpio44\# echo 1 > value

5. 查看输出值

/sys/class/gpio/gpio44\# cat value

6. 取消导出

/sys/class/gpio\# echo 44 > unexport

文件读写例程：

\#include stdlib.h

\#include stdio.h

\#include string.h

\#include unistd.h

\#include fcntl.h   //define O\_WRONLY and O\_RDONLY

//芯片复位引脚: P1\_16

\#define SYSFS\_GPIO\_EXPORT           "/sys/class/gpio/export"

\#define SYSFS\_GPIO\_RST\_PIN\_VAL      "48"

\#define SYSFS\_GPIO\_RST\_DIR          "/sys/class/gpio/gpio48/direction"

\#define SYSFS\_GPIO\_RST\_DIR\_VAL      "OUT"

\#define SYSFS\_GPIO\_RST\_VAL          "/sys/class/gpio/gpio48/value"

\#define SYSFS\_GPIO\_RST\_VAL\_H        "1"

\#define SYSFS\_GPIO\_RST\_VAL\_L        "0"

int main()

int fd;

//打开端口/sys/class/gpio\# echo 48 > export

fd = open(SYSFS\_GPIO\_EXPORT, O\_WRONLY);

if(fd == -1)

printf("ERR: Radio hard reset pin open error.\\n");

return EXIT\_FAILURE;

write(fd, SYSFS\_GPIO\_RST\_PIN\_VAL ,sizeof(SYSFS\_GPIO\_RST\_PIN\_VAL));

close(fd);

//设置端口方向/sys/class/gpio/gpio48\# echo out > direction

fd = open(SYSFS\_GPIO\_RST\_DIR, O\_WRONLY);

if(fd == -1)

printf("ERR: Radio hard reset pin direction open error.\\n");

return EXIT\_FAILURE;

write(fd, SYSFS\_GPIO\_RST\_DIR\_VAL, sizeof(SYSFS\_GPIO\_RST\_DIR\_VAL));

close(fd);

//输出复位信号: 拉高>100ns

fd = open(SYSFS\_GPIO\_RST\_VAL, O\_RDWR);

if(fd == -1)

printf("ERR: Radio hard reset pin value open error.\\n");

return EXIT\_FAILURE;

while(1)

write(fd, SYSFS\_GPIO\_RST\_VAL\_H, sizeof(SYSFS\_GPIO\_RST\_VAL\_H));

usleep(1000000);

write(fd, SYSFS\_GPIO\_RST\_VAL\_L, sizeof(SYSFS\_GPIO\_RST\_VAL\_L));

usleep(1000000);

close(fd);

printf("INFO: Radio hard reset pin value open error.\\n");

return 0;

另外参考网上一个网友的程序，这里做了验证，并实现中断检测函数。如下：

\#include stdlib.h

\#include stdio.h

\#include string.h

\#include unistd.h

\#include fcntl.h

\#include poll.h

\#define MSG(args...) printf(args)

//函数声明

static int gpio\_export(int pin);

static int gpio\_unexport(int pin);

static int gpio\_direction(int pin, int dir);

static int gpio\_write(int pin, int value);

static int gpio\_read(int pin);

static int gpio\_export(int pin)

char buffer\[64\];

int len;

int fd;

fd = open("/sys/class/gpio/export", O\_WRONLY);

if (fd < 0) \{

MSG("Failed to open export for writing!\\n");

return(-1);

len = snprintf(buffer, sizeof(buffer), "%d", pin);

if (write(fd, buffer, len) < 0) \{

MSG("Failed to export gpio!");

return -1;

close(fd);

return 0;

static int gpio\_unexport(int pin)

char buffer\[64\];

int len;

int fd;

fd = open("/sys/class/gpio/unexport", O\_WRONLY);

if (fd < 0) \{

MSG("Failed to open unexport for writing!\\n");

return -1;

len = snprintf(buffer, sizeof(buffer), "%d", pin);

if (write(fd, buffer, len) < 0) \{

MSG("Failed to unexport gpio!");

return -1;

close(fd);

return 0;

//dir: 0-->IN, 1-->OUT

static int gpio\_direction(int pin, int dir)

static const char dir\_str\[\] = "in\\0out";

char path\[64\];

int fd;

snprintf(path, sizeof(path), "/sys/class/gpio/gpio%d/direction", pin);

fd = open(path, O\_WRONLY);

if (fd < 0) \{

MSG("Failed to open gpio direction for writing!\\n");

return -1;

if (write(fd, &dir\_str\[dir == 0 ? 0 : 3\], dir == 0 ? 2 : 3) < 0) \{

MSG("Failed to set direction!\\n");

return -1;

close(fd);

return 0;

//value: 0-->LOW, 1-->HIGH

static int gpio\_write(int pin, int value)

static const char values\_str\[\] = "01";

char path\[64\];

int fd;

snprintf(path, sizeof(path), "/sys/class/gpio/gpio%d/value", pin);

fd = open(path, O\_WRONLY);

if (fd < 0) \{

MSG("Failed to open gpio value for writing!\\n");

return -1;

if (write(fd, &values\_str\[value == 0 ? 0 : 1\], 1) < 0) \{

MSG("Failed to write value!\\n");

return -1;

close(fd);

return 0;

static int gpio\_read(int pin)

char path\[64\];

char value\_str\[3\];

int fd;

snprintf(path, sizeof(path), "/sys/class/gpio/gpio%d/value", pin);

fd = open(path, O\_RDONLY);

if (fd < 0) \{

MSG("Failed to open gpio value for reading!\\n");

return -1;

if (read(fd, value\_str, 3) < 0) \{

MSG("Failed to read value!\\n");

return -1;

close(fd);

return (atoi(value\_str));

// none表示引脚为输入，不是中断引脚

// rising表示引脚为中断输入，上升沿触发

// falling表示引脚为中断输入，下降沿触发

// both表示引脚为中断输入，边沿触发

// 0-->none, 1-->rising, 2-->falling, 3-->both

static int gpio\_edge(int pin, int edge)

const char dir\_str\[\] = "none\\0rising\\0falling\\0both";

char ptr;

char path\[64\];

int fd;

switch(edge)\{

case 0:

ptr = 0;

break;

case 1:

ptr = 5;

break;

case 2:

ptr = 12;

break;

case 3:

ptr = 20;

break;

default:

ptr = 0;

snprintf(path, sizeof(path), "/sys/class/gpio/gpio%d/edge", pin);

fd = open(path, O\_WRONLY);

if (fd < 0) \{

MSG("Failed to open gpio edge for writing!\\n");

return -1;

if (write(fd, &dir\_str\[ptr\], strlen(&dir\_str\[ptr\])) < 0) \{

MSG("Failed to set edge!\\n");

return -1;

close(fd);

return 0;

//GPIO1\_17

int main()

int gpio\_fd, ret;

struct pollfd fds\[1\];

char buff\[10\];

unsigned char cnt = 0;

//LED引脚初始化

gpio\_export(115);

gpio\_direction(115, 1);

gpio\_write(115, 0);

//按键引脚初始化

gpio\_export(49);

gpio\_direction(49, 0);

gpio\_edge(49,1);

gpio\_fd = open("/sys/class/gpio/gpio49/value",O\_RDONLY);

if(gpio\_fd < 0)\{

MSG("Failed to open value!\\n");

return -1;

fds\[0\].fd = gpio\_fd;

fds\[0\].events  = POLLPRI;

ret = read(gpio\_fd,buff,10);

if( ret == -1 )

MSG("read\\n");

while(1)\{

ret = poll(fds,1,0);

if( ret == -1 )

MSG("poll\\n");

if( fds\[0\].revents & POLLPRI)\{

ret = lseek(gpio\_fd,0,SEEK\_SET);

if( ret == -1 )

MSG("lseek\\n");

ret = read(gpio\_fd,buff,10);

if( ret == -1 )

MSG("read\\n");

gpio\_write(115, cnt++%2);

usleep(100000);

return 0;

参考文档：

[http://blog.csdn.net/xukai871105/article/details/38456079][http_blog.csdn.net_xukai871105_article_details_38456079]

[http://blog.csdn.net/sukhoi27smk/article/details/26447765][http_blog.csdn.net_sukhoi27smk_article_details_26447765]

[https_blog.csdn.net_ruanjianruanjianruan_article_details_47734397]: https://blog.csdn.net/ruanjianruanjianruan/article/details/47734397
[linux_GPIO]: https://blog.csdn.net/u010871058/article/details/65648593
[Link 1]: http://lib.csdn.net/base/embeddeddevelopment
[Linux]: http://lib.csdn.net/base/linux
[Center]: /images/20220309/ca371c7dae7a419abdb25c51e3b65cc7.png
[Center 1]: /images/20220309/c558cd1517434b20a6e05db680ebe3bf.png
[LED]: https://www.baidu.com/s?wd=LED%E7%81%AF&tn=24004469_oem_dg&rsv_dl=gh_pl_sl_csd
[http_blog.sina.com.cn_s_blog_7880d3350102w2um.html]: http://blog.sina.com.cn/s/blog_7880d3350102w2um.html
[http_blog.csdn.net_xukai871105_article_details_38456079]: http://blog.csdn.net/xukai871105/article/details/38456079
[http_blog.csdn.net_sukhoi27smk_article_details_26447765]: http://blog.csdn.net/sukhoi27smk/article/details/26447765