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LINUX GPIO 基操之应用层操作gpio

时间：2022-02-03 16:28:28

LINUX GPIO 基操之应用层

应用层sysfs操作GPIO相关文件节点介绍如何编写应用程序操作GPIO如何通过寄存器操作GPIO

注：所有文章基于linux-3.13 以上，本系列主要介绍 GPIO的一些基本知识，驱动操作GPIO的接口，应用层通过sysfs操作GPIO的接口，GPIO一些debug信息查看，以及对高通相关GPIO的寄存器操作。分享给刚刚接触外设bsp的小伙伴们。当然后面有时间还会分享GPIO子系统框架和pinctrl子系统框架，先知道黑盒怎么使用，然后咱再打开仔细瞅瞅。有错误不正当点，勿喷，还请指出，一起修改，谢谢！！

本篇为应用层控制接口篇，主要分享，应用层对gpio的操作和如何通过寄存器操作gpio（主要介绍高通的寄存器方式）。

应用层sysfs操作GPIO

如何编写应用程序操作GPIO

我们完全可以通过调用system的方式实现上面提到的前三种操作,但是无法实现中断的监控，而且system方式太消耗资源。linux里面万物皆文件，下面重点介绍如何通过open，write，poll等方式对gpio进行操作。

1）需要包含的头文件

#include stdlib.h #include stdio.h #include string.h#include unistd.h#include fcntl.h #include poll.h

2）导出一个节点

tatic 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; }

3）销毁一个节点

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; }

4）读写一个节点

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));} //value: 0-->LOW, 1-->HIGHstatic 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; }

5）设置方向

//dir: 0-->IN, 1-->OUTstatic 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; }

6）中断方式设置

// 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-->bothstatic 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; }

7）监控一个gpio中断