WhyCan Forum(哇酷开发者社区)

如题：
代码如下：
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <fcntl.h>
#include <asm/termios.h>
#include <memory.h>

#define DEV_NAME  "/dev/ttyS7"

int main (int argc, char *argv[])
{
    int fd;
    int len, i,ret;
    char buf[] = "Hello TopSemic! \n";

    fd = open(DEV_NAME, O_RDWR | O_NOCTTY|O_NDELAY);
    if(fd < 0)
    {
        perror(DEV_NAME);
        return -1;
    }

    len = write(fd, buf, sizeof(buf));
    if (len < 0)
    {
        printf("write data error \n");
    }

    while(1)
    {
        memset(buf,0x00,sizeof(buf));
        len = read(fd, buf, sizeof(buf));
        printf("len = %d\r\n", len);

        usleep(500000);
    }
}