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 *** 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 *** 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
}
swap分区，具体步骤如下：1)使用dd命令创建一个swap分区
1 [root@cms home]# dd if=/dev/zero of=/home/swap bs=1024 count=8192000
2 8192000+0 records in
3 8192000+0 records out
4 8388608000 bytes (8.4 GB) copied, 33.5006 s, 250 MB/s
这样就创建了一个分区大小为8G的/home/swap文件，接下来格式化该分区文件。
2)格式化/home/swap文件。
1 [root@cms home]# mkswap /home/swap
2 mkswap: /home/swap: warning: don't erase bootbits sectors
3 on whole disk. Use -f to force.
4 Setting up swapspace version 1, size = 8191996 KiB
5 no label, UUID=4ae031dd-eefe-43ba-8fb0-c09719d896b6
3)用swapon命令把/home/swap文件分区划成swap分区
1 [root@cms home]# swapon /home/swap
2 [root@cms home]# free -m
3 total used free sharedbuffers cached
4 Mem: 7872 7730142 0 70 6394
5 -/+ buffers/cache: 1264 6608
6 Swap: 7999 0 7999
4)修改/etc/fstab文件添加/home/swap swap swap default 0 0，即使重启也能自动挂载。
1 [root@cms home]# vi /etc/fstab
2 #
3 # /etc/fstab
4 # Created by anaconda on Tue Jan 26 21:10:02 2016
5 #
6 # Accessible filesystems, by reference, are maintained under '/dev/disk'
7 # See man pages fstab(5), findfs(8), mount(8) and/or blkid(8) for more info
8 #
9 UUID=f8cb78d5-8419-4bcf-8684-9e8a94480f22 / ext4defaults1 1
10 UUID=9e4bacd3-490c-4e87-a5e0-fec240a3e229 /usrxfs defaults1 2
11 tmpfs /dev/shmtmpfs defaults0 0
12 devpts /dev/ptsdevpts gid=5,mode=620 0 0
13 sysfs /syssysfs defaults0 0
14 proc/proc procdefaults0 0
15 /home/swap swapswapdefault 0 0
16 "/etc/fstab" 16L, 788C writte
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