linux c++串口回显输出

In my program which sends bytes to a serial port, I receive bytes which I send. I don't want to receive bytes which I send, and I don't know how to do this?

在我的程序中，将字节发送到串行端口，我接收我发送的字节。我不想接收我发送的字节，我不知道怎么做?

#include <stdio.h>
#include <fcntl.h>
#include <termios.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <sys/time.h>
#include <sys/select.h>
#include <sys/ioctl.h>

int fd;
struct termios tio, old_tio;

time_t SubTime_mSec(timeval val1, timeval val2)
{
    timeval tv;
    if (val1.tv_sec > val2.tv_sec) return (0);
    if (val1.tv_sec == val2.tv_sec)
        if (val1.tv_usec > val2.tv_usec) return (0);
    tv.tv_sec = val2.tv_sec - val1.tv_sec;
    if (val1.tv_usec < val2.tv_usec) {
        tv.tv_usec = val2.tv_usec - val1.tv_usec;
    } else {
        tv.tv_sec --;
        tv.tv_usec = 1000000 + val2.tv_usec - val1.tv_usec;
    }

    return(tv.tv_sec*1000 + tv.tv_usec/1000);
}


void RTUOutMessage(int cnt1, int cnt2)
{
    unsigned char msg[13] = {0x01, 0x10, 0x00, 0x2F, 0x00, 0x02, 0x04, 0x4B, 0x64, 0x3D, 0xD9, 0x36, 0xC6};
    int Len = 13;
    int status, i, j;
    ioctl(fd, TIOCMGET, &status);

    status = status | TIOCM_RTS | TIOCM_DTR;
    ioctl(fd, TIOCMSET, &status);
    write(fd, msg, Len);
    for (j = 0; j < cnt1; j ++)
        for (i = 0; i < cnt2; i ++);
    ioctl(fd, TIOCMGET, &status);
    status &= ~TIOCM_RTS;
    status &= ~TIOCM_DTR;
    ioctl(fd, TIOCMSET, &status);

    timeval start_t, curr_t;
    char Buff[80];
    int l;

    gettimeofday(&start_t, NULL);
    curr_t = start_t;
    while (SubTime_mSec(start_t, curr_t) < 1000) {
        l = read(fd, Buff, 80);
        if (l > 0) {
            printf("BUFFER=");
             for(i = 0; i < l; i++) {
                 printf(" %x", Buff[i]);
             }
             //printf("\n");
        }
        gettimeofday(&curr_t, NULL);
    }
}

void  InitPort(void)
{
    int StopBits = 2;
    if ((fd = open("/dev/ttyAM2", O_RDWR | O_NDELAY)) < 0) {
        printf("Couldn't open //dev//ttyAM2\n");
    }
    tcflush(fd, TCIOFLUSH);
    int n = fcntl(fd, F_GETFL, 0);
    fcntl(fd, F_SETFL, n & ~O_NDELAY);
    tcgetattr(fd, &old_tio);
    tcgetattr(fd, &tio);
    cfsetospeed(&tio, (speed_t)B9600);
    cfsetispeed(&tio, (speed_t)B9600);
    tio.c_cflag = (tio.c_cflag & ~CSIZE) | CS8;
    tio.c_cflag |= CLOCAL | CREAD ;
    tio.c_cflag &= ~OFILL; 
    //parity
    tio.c_cflag &= ~(PARENB | PARODD);
    tio.c_cflag &= ~CRTSCTS;
    if (StopBits == 2) tio.c_cflag |= CSTOPB;
    else tio.c_cflag &= ~CSTOPB;
    tio.c_iflag=IGNBRK;
    tio.c_iflag &= ~(IXON|IXOFF|IXANY);
    tio.c_lflag=0;
    tio.c_oflag=0;
    tio.c_cc[VTIME]=0;
    tio.c_cc[VMIN]=0;
    if (tcsetattr(fd, TCSANOW, &tio)!=0) printf("tcsetattr() 1 failed\n");

    int mcs=0;
    ioctl(fd, TIOCMGET, &mcs);
    mcs |= TIOCM_RTS;
    ioctl(fd, TIOCMSET, &mcs);

    if (tcgetattr(fd, &tio)!=0) printf("tcgetattr() 4 failed\n");
    tio.c_cflag &= ~CRTSCTS;
    if (tcsetattr(fd, TCSANOW, &tio)!=0) printf("tcsetattr() 2 failed\n");
}

int main(int argc, char **argv)
{
    InitPort();
    int cnt1, cnt2;
    cnt1 = 3;
    cnt2 = 20000;
    cnt1 = atoi(argv[1]);
    cnt2 = atoi(argv[2]);
    for(;;) {
    RTUOutMessage(cnt1, cnt2);
    usleep(1000000);
    }
    tcsetattr(fd, TCSANOW, &old_tio);
    close(fd);
    printf("End\n");

    return 0;
}

1 个解决方案

#1

If you are receiving the chars that you sent, then the remote's serial port is apparently echoing its input.

如果您正在接收所发送的字符，那么远程程序的串行端口显然是在响应其输入。

You will either have to disable input echo at the other device, or perform "echo cancellation" in your receive logic. I.E. create an "echo FIFO". Each byte output to the serial port is also written to the "echo FIFO". Set a flag indicating that an echo is expected. As input is received, compare it to the "echo FIFO", and remove chars when it matches, and toss the receive char. If no match, then accept receive char. Clear the echo flag when the "echo FIFO" is empty.

您将不得不在另一个设备上禁用输入echo，或者在接收逻辑中执行“echo cancel”。创建一个“echo FIFO”。串行端口的每个字节输出也被写入“echo FIFO”。设置一个标志，指示期望出现回音。当接收到输入时，将其与“echo FIFO”进行比较，并在匹配时删除chars，并抛出接收char。如果没有匹配，则接受接收字符。当“echo FIFO”为空时清除echo标志。

BTW the code appears to set the serial port to raw or non-canonical mode. The preferred method would be to use

顺便说一下，代码似乎将串行端口设置为原始模式或非规范模式。首选的方法是使用

cfmakeraw(&tio);

rather than

而不是

tio.c_iflag=IGNBRK;
tio.c_iflag &= ~(IXON|IXOFF|IXANY);
tio.c_lflag=0;
tio.c_oflag=0;

#1