概述：
在linux编程中我们经常会听到“一切皆文件”这句话，其实串口编程也只是拿到一个文件描述符，有数据发送过来我们就可以读到数据，利用libev的io操作，我们就可以实现epoll事件轮询，有数据就会产生回调不需要傻傻在那里sleep轮询检测。对于使用虚拟机和windows串口通信可以看我之前写的这篇文章。
实例Demo:
#include <stdio.h>
#include <stdint.h>
#include <unistd.h>
#include <string.h>
#include <time.h>
#include <termios.h>
#include <fcntl.h>
#include <errno.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <ev.h>
#define UART_PORT "/dev/ttyS1"
#define UART_SPEED 115200
#define UART_DATA_BIT 8
#define UART_STOP_BIT 1
#define UART_CHECK_BIT 0
typedef struct {
int fd;
char uart_buff[256];
}uart_ctrl_t;
/*串口初始化*/
int uart_init(uart_ctrl_t *uart_ctrl, int speed, int data_bit, int stop, int check)
{
struct termios opt;
uart_ctrl->fd = open(UART_PORT, O_RDWR | O_NOCTTY | O_NDELAY);
if (-1 == uart_ctrl->fd) {
printf("open uart %s failed\r\n", UART_PORT);
goto err1;
}
if (0 != tcgetattr(uart_ctrl->fd, &opt)) {
goto err2;
}
//设置数据位
opt.c_cflag &= ~CSIZE;
switch (data_bit) {
case 5:
opt.c_cflag |= CS5;
break;
case 6:
opt.c_cflag |= CS6;
break;
case 7:
opt.c_cflag |= CS7;
break;
case 8:
opt.c_cflag |= CS8;
break;
default:
opt.c_cflag |= CS8;
break;
}
//设置停止位
if (2 == stop) {
//2个停止位
opt.c_cflag |= CSTOPB;
} else {
//默认1个停止位
opt.c_cflag &= ~CSTOPB;
}
//设置校验位
switch (check) {
case 1:
//奇校验
opt.c_cflag |= PARENB;
opt.c_cflag |= PARODD;
//INPCK打开输入奇偶校验；ISTRIP去除字符的第八个比特
opt.c_iflag |= (INPCK | ISTRIP);
case 2:
//偶校验
opt.c_cflag |= PARENB;
opt.c_cflag &= ~PARODD;
//INPCK打开输入奇偶校验；ISTRIP去除字符的第八个比特
opt.c_iflag |= (INPCK | ISTRIP);
default:
//默认无校验
opt.c_cflag &= ~PARENB;
break;
}
//设置波特率
switch (speed) {
case 19200:
if (-1 == cfsetispeed(&opt, B19200)) {
goto err2;
}
if (-1 == cfsetospeed(&opt, B19200)) {
goto err2;
}
break;
case 115200:
if (-1 == cfsetispeed(&opt, B115200)) {
goto err2;
}
if (-1 == cfsetospeed(&opt, B115200)) {
goto err2;
}
break;
default:
//默认9600
if (-1 == cfsetispeed(&opt, B9600)) {
goto err2;
}
if (-1 == cfsetospeed(&opt, B9600)) {
goto err2;
}
break;
}
//部分模式设置
opt.c_lflag &= ~(ICANON | ECHO | ECHOE | ISIG);
opt.c_oflag &= ~OPOST;
opt.c_iflag &= ~(BRKINT | INPCK | ISTRIP | ICRNL| IGNCR | IXON);
//清除输入输出数据
tcflush(uart_ctrl->fd, TCIOFLUSH);
//激活配置生效
if(0 != tcsetattr(uart_ctrl->fd, TCSANOW, &opt)) {
goto err2;
}
return 0;
err2:
close(uart_ctrl->fd);
err1:
return -1;
}
/*串口事件回调*/
static void watcher_uart_cb (struct ev_loop *loop ,struct ev_io *w, int revents)
{
void *user_data = ev_userdata(loop);
uart_ctrl_t *uart_ctrl = (uart_ctrl_t *)user_data;
int bytes = read(uart_ctrl->fd, uart_ctrl->uart_buff, 32);
if (-1 == bytes) {
return ;
}
/*
测试demo,此处不够严谨，真实使用需要临时缓冲然后拷贝到处理数据buffer中.
有时数据传输过多，并不能一次性读完数据就会截断，故最好使用时开一个数据缓存存储，再处理.
*/
uart_ctrl->uart_buff[bytes] = '\0';
printf("%s\r\n", uart_ctrl->uart_buff);
char *res = "OK\r\n";
write(uart_ctrl->fd, res, strlen(res)+1);
}
/*事件循环初始化*/
struct ev_loop* main_loop_init(uart_ctrl_t *uart_ctrl)
{
static struct ev_io uart_watcher;
struct ev_loop *loop = ev_loop_new(EVBACKEND_EPOLL);
if (NULL == loop) {
printf("create loop failed\r\n");
return NULL;
}
//传参
ev_set_userdata(loop, uart_ctrl);
//初始化
ev_io_init (&uart_watcher, watcher_uart_cb, uart_ctrl->fd, EV_READ);
ev_io_start (loop, &uart_watcher);
return loop;
}
int main()
{
uart_ctrl_t uart_ctrl;
if (0 != uart_init(&uart_ctrl, UART_SPEED, UART_DATA_BIT, UART_STOP_BIT, UART_CHECK_BIT)) {
printf("uart init failed\r\n");
return -1;
}
struct ev_loop* loop = main_loop_init(&uart_ctrl);
if (NULL == loop) {
printf("loop init failed\r\n");
return -1;
}
ev_run(loop, 0);
close(uart_ctrl.fd);
return 0;
}
编译：
//编译
gcc -o ev_uart ev_uart.c -lev运行结果:
