int main(void)
{
    char *portname = "/dev/ttyO4";

    int fd = open (portname, O_RDWR | O_NOCTTY | O_SYNC);
    if (fd < 0)
    {
        printf ("error %d opening %s: %s", errno, portname, strerror (errno));
        return 0;
    }

    set_interface_attribs (fd, BAUD_RATE, 0);
    set_blocking (fd, 0);

    tcflush(fd, TCIOFLUSH);

    char s[] = {0x65};
    std::string ans = "";

    while (true)
    {
        write (fd, s, 1);
        char buf[100];
        int n = read (fd, buf, 99);
        std::cout << buf;
        std::cout.flush();
        sleep(1);
    }

    return 0;
}