openwrt 亲测可用串口实例

#include     
#include      
#include       
#include     
#include     
#include      
#include     
#include     
#include     

  
int main()
{
    int fd;
    int i;
    int len;
    int n = 0;      
    char read_buf[20];
    char write_buf[20];
    char testbuff[]="Hello1263\r\n";
    struct termios opt; 
    fd = open("/dev/ttyUSB2", O_RDWR | O_NOCTTY);    //默认为阻塞读方式
    write(fd,testbuff,10);
   
    tcgetattr(fd, &opt);      

    cfsetispeed(&opt, B9600);
    cfsetospeed(&opt, B9600);

    if(tcsetattr(fd, TCSANOW, &opt) != 0 )
    {     
       perror("tcsetattr error");
       return -1;
    }
    
    opt.c_cflag &= ~CSIZE;  
    opt.c_cflag |= CS8;   
    opt.c_cflag &= ~CSTOPB; 
    opt.c_cflag &= ~PARENB; 
    
    opt.c_iflag &= ~INPCK;//opt.c_cflag &= ~INPCK;the last this is fetal set
    opt.c_cflag |= (CLOCAL | CREAD);
 
    opt.c_lflag &= ~(ICANON | ECHO | ECHOE | ISIG);
 
    opt.c_oflag &= ~OPOST;
    opt.c_oflag &= ~(ONLCR | OCRNL);    //添加的
 
    opt.c_iflag &= ~(ICRNL | INLCR);
    opt.c_iflag &= ~(IXON | IXOFF | IXANY);    //添加的
    
    opt.c_cc[VTIME] = 0;
    opt.c_cc[VMIN] = 0;
    
    tcflush(fd, TCIOFLUSH);
 
    printf("configure complete\n");
   
    if(tcsetattr(fd, TCSANOW, &opt) != 0)
    {
        perror("serial error");
        return -1;
    } 
  
    while(1)
    {    
        n = 0;
        len = 0;
        bzero(read_buf, sizeof(read_buf));    //类似于memset
        bzero(write_buf, sizeof(write_buf));
	
	while( (n = read(fd, read_buf, sizeof(read_buf))) > 1 )//>0
        {
	    printf("n= %d \n", n);//
            for(i = len; i < (len + n); i++)
            {
                write_buf[i] = read_buf[i - len];
            }
            len += n;    
        }
        write_buf[len] = '\0';
	write_buf[1]=write_buf[0];  
        n = write(fd, write_buf, len);
	printf("have sended\n");
        sleep(2);
    }
}

把接收到的字符串第二个字符改成第一个字符，用于验证。串口配置项很重要，需要理解其意。

https://blog.csdn.net/baweiyaoji/article/details/72885633

结构体和函数详细讲解https://wenku.baidu.com/view/33dc137a6bd97f192379e932.html