通过RS232读取和写入未收到第一个字符串

Question

我使用mini2440板，通过RS232在PC（ubuntu）和板之间进行通信。 我的代码在这里，我从ubuntu服务器11.04连接到mini2440板。通过RS232读取和写入未收到第一个字符串。如何收到所有字符串？

从com端口读取代码：

// "rs232_recv.c"
#include "sys/types.h"
#include "sys/stat.h"
#include "fcntl.h"
#include "termios.h"
#include "stdio.h"

#define BAUDRATE B38400
#define MODEMDEVICE "/dev/ttyS1"
#define _POSIX_SOURCE 1

int main()
{
    int fd, c=0, res;
    struct termios oldtio, newtio;
    char buf[256];

    printf("Start...\n");
    fd = open(MODEMDEVICE, O_RDWR|O_NOCTTY);

    if (fd < 0) {
        perror(MODEMDEVICE);
        exit(1);
    }

    printf("Open...\n");
    tcgetattr(fd, &oldtio);
    bzero(&newtio, sizeof(newtio));

    newtio.c_cflag = BAUDRATE|CS8|CLOCAL|CREAD;
    newtio.c_iflag = IGNPAR;
    newtio.c_oflag = 0;
    newtio.c_lflag = ICANON;

    tcflush(fd, TCIFLUSH);
    tcsetattr(fd, TCSANOW, &newtio);
    printf("Reading...\n");

    while(1) {
        res = read(fd, buf, 255);
        buf[res]=0;
        printf("res=%d buf=%s\n", res, buf);

        if (buf[0] == '@')
            break;
    }


    printf("Close...\n");
    close(fd);
    tcsetattr(fd, TCSANOW, &oldtio);

    return 0;
}

写入com端口的代码

// "rs232_send.c"

#include "sys/types.h"
#include "sys/stat.h"
#include "fcntl.h"
#include "termios.h"
#include "stdio.h"

#define BAUDRATE B38400
#define MODEMDEVICE "/dev/ttyS0"
#define _POSIX_SOURCE 1
#define STOP '@'

int main()
{
    int fd, c=0, res;
    struct termios oldtio, newtio;
    char ch;
    static char s1[20];

    printf("Start...\n");
    fd = open(MODEMDEVICE, O_RDWR|O_NOCTTY);

    if (fd < 0) {
        perror(MODEMDEVICE);
        exit(1);
    }

    printf("Open...\n");
    tcgetattr(fd, &oldtio);
    bzero(&newtio, sizeof(newtio));

    newtio.c_cflag = BAUDRATE|CS8|CLOCAL|CREAD;
    newtio.c_iflag = IGNPAR;
    newtio.c_oflag = 0;
    newtio.c_lflag = ICANON;

    tcflush(fd, TCIFLUSH);
    tcsetattr(fd, TCSANOW, &newtio);

    printf("Writing...\n");

    while(1) {
        while((ch=getchar()) != STOP) {
            s1[0]=ch;
            res=write(fd, s1, 1); 
        }

        s1[0]=ch;
        s1[1]='\n';
        res = write(fd, s1, 2); 

        break;
    }

    printf("Close...\n");
    close(fd);
    tcsetattr(fd, TCSANOW, &oldtio);

    return 0;
}