串口：卡在 read()

Question

我有一个 C++ 程序，它读取 IMU 设备并在经过一些处理后将数据写入文件。 速率很高，每秒 500 行。该程序似乎工作正常，但它随机停止读取串行端口。

经过一番研究，它似乎卡在了读取命令中：

while((res += read(IMU, header, 3)) != 3).

这怎么会发生，我该如何防止这种情况发生？

如果您需要任何其他信息，请告诉我。

void* imuLogger(void* arg) {
IMU = initSerial("/dev/ttyUSB0", B115200);
openLog("logIMU", IMUfile);
int res;
char tmp;
char header[3];

while(true)
{
    gettimeofday(&ts, NULL);
    timeLog = (ts.tv_sec * 1000000 + ts.tv_usec) - timeStart;

    /**** READ IMU ****/
    res = 0;
    cout << indexLog << "-"<< IMU<< endl;
    while((res += read(IMU, header, 3)) != 3);
    cout << indexLog << "entered loop"<< endl;
    string head(header, 3);


    if(head.compare("snp") == 0 || head.substr(1, 2).compare("np") == 0 || head.substr(0, 2).compare("sn") == 0 || (header[0] == 's' && header[2] == 'p'))
    {

        buf[0] = 's';
        buf[1] = 'n';
        buf[2] = 'p';

        while((res = read(IMU, &tmp, 1)) != 1);
        buf[3] = tmp;

        res = 4;
        while(res < sizeof(buf))
            res += read(IMU, buf + res, sizeof(buf) - res);

        parseData();
    }
    else if(head.substr(0, 2).compare("np") == 0)
    {

        buf[0] = 's';
        buf[1] = 'n';

        buf[3] = buf[2];
        buf[2] = 'p';

        res = 4;
        while(res < sizeof(buf))
            res += read(IMU, buf + res, sizeof(buf) - res);

        parseData();
    }
    else if(head.substr(1,2).compare("sn") == 0)
    {

        buf[0] = 's';
        buf[1] = 'n';
        buf[2] = 'p';

        while((res = read(IMU, &tmp, 1)) != 1);
        while((res = read(IMU, &tmp, 1)) != 1);
        buf[3] = tmp;

        res = 4;
        while(res < sizeof(buf))
            res += read(IMU, buf + res, sizeof(buf) - res);

        parseData();
    }
    else
    {
        //tcflush(IMU, TCIOFLUSH);
        //while((res = read(IMU, header, 1)) != 1)
        //  cout << 
        cout << "Error parser\n";
    }
//parseData();
        //gettimeofday(&ts, NULL);
        //timeEnd = (ts.tv_sec * 1000000 + ts.tv_usec) - time - timeStart;
        //cout << "Length:" << res << " Time:" << timeEnd << " Address:" << (int)packet.Address << endl;
        //usleep(10000 - timeEnd);

//cout <<"entered"<< endl;
    }
return 0;
}

int main() {

    signal(SIGINT, exit_handler);

    gettimeofday(&ts, NULL);
    timeStart = ts.tv_sec * 1000000 + ts.tv_usec;

    pthread_create(&imuThread, NULL, imuLogger, NULL);
    pthread_create(&rpmThread, NULL, rpmLogger, NULL);
    //pthread_create(&baroThread, NULL, baroLogger, NULL);

    while(true)
    { 
        gettimeofday(&ts4, NULL);
        timeLog_main = (ts4.tv_sec * 1000000 + ts4.tv_usec) - timeStart;
        cout << timeLog_main/1e6 << endl;
        sleep(1);
    }

    return 0;
}

Answer 1

如果 read() 第一次返回 1 个字节，第二次返回 3 个字节，则 res 永远不会是 3。