Programming

   Canonical and non-canonical mode
       The  setting of the ICANON canon flag in c_lflag determines whether the
       terminal is operating in canonical mode (ICANON set)  or  non-canonical
       mode (ICANON unset).  By default, ICANON set.

       In canonical mode:

       * Input  is  made  available  line by line.  An input line is available
         when one of the line delimiters is typed (NL, EOL, EOL2;  or  EOF  at
         the start of line).  Except in the case of EOF, the line delimiter is
         included in the buffer returned by read(2).

       * Line editing is enabled (ERASE, KILL; and if the IEXTEN flag is  set:
         WERASE,  REPRINT,  LNEXT).   A  read(2)  returns  at most one line of
         input; if the read(2) requested fewer bytes than are available in the
         current line of input, then only as many bytes as requested are read,
         and the remaining characters will be available for a future read(2).

       In non-canonical mode input is available immediately (without the  user
       having  to  type  a line-delimiter character), and line editing is dis-
       abled.  The settings of MIN (c_cc[VMIN]) and TIME (c_cc[VTIME])  deter-
       mine  the  circumstances  in  which a read(2) completes; there are four
       distinct cases:

       * MIN == 0; TIME == 0: If data is available,  read(2)  returns  immedi-
         ately,  with the lesser of the number of bytes available, or the num-
         ber of bytes requested.  If no data is available, read(2) returns 0.

       * MIN > 0; TIME == 0: read(2) blocks until the lesser of MIN  bytes  or
         the  number  of bytes requested are available, and returns the lesser
         of these two values.

       * MIN == 0; TIME > 0: TIME specifies the limit for a timer in tenths of
         a  second.   The  timer  is  started when read(2) is called.  read(2)
         returns either when at least one byte of data is available,  or  when
         the  timer  expires.  If the timer expires without any input becoming
         available, read(2) returns 0.

       * MIN > 0; TIME > 0: TIME specifies the limit for a timer in tenths  of
         a second.  Once an initial byte of input becomes available, the timer
         is restarted after each further byte is  received.   read(2)  returns
         either  when  the lesser of the number of bytes requested or MIN byte
         have been read, or when the inter-byte timeout expires.  Because  the
         timer  is  only  started after the initial byte becomes available, at
         least one byte will be read.

bool cClassSerialLIB::OpenPort(bool bloccante)
{
      // make sure port is closed
      ClosePort();
      //ttymxc4
      QByteArray Porta_byte_array = Porta.toLatin1();
      const char* Porta_char=Porta_byte_array.data();
      fd = open(Porta_char/*"/dev/ttymxc4"*/, O_RDWR |
                          O_NOCTTY | /* tells UNIX that this program doesn't want to be the "controlling terminal" for that port*/
                          O_NDELAY); /* tells UNIX that this program doesn't care what state the DCD signal line is in */

      if (fd < 0)
      {
          qDebug("errore in apertura %d %s\n", errno, strerror(errno));
          return false;
      }
      else
      {
          qDebug("ok %d",fd);
          struct termios options;

          /* The FNDELAY option causes the read function to return 0 if no
            characters are available on the port. To restore normal (blocking) behavior,
            call fcntl() without the FNDELAY option: */

          if(bloccante)
          {
              printf("bloccante\n");
              fcntl(fd, F_SETFL, 0);
          }
          else
          {
             printf("NON bloccante");
             fcntl(fd, F_SETFL, FNDELAY);
          }

          //cfmakeraw(&options); //ABILITARLO NEL CASO DI ERRORE!


          tcgetattr(fd, &options);

          //set port speed 115200
          cfsetispeed(&options, B115200);
          cfsetospeed(&options, B115200);

          options.c_cflag |= (CLOCAL | CREAD);

          //set 8n1

          options.c_cflag &= ~PARENB; /* Enable parity bit */
          options.c_cflag &= ~CSTOPB; /* 2 stop bits (1 otherwise) */
          options.c_cflag &= ~CSIZE; /* Mask the character size bits */
          options.c_cflag |= CS8; /* Select 8 data bits */

          options.c_iflag &= ~IXON; //RIMUOVE X0N/XOFF control
          options.c_iflag &= ~IXOFF;
          options.c_iflag &= ~IGNCR;

          //set raw input
          options.c_lflag &= ~(ICANON |   /*Enable canonical input (else raw)*/
                                  ECHO |  /*Enable echoing of input characters*/
                                  ECHOE | /*Echo erase character as BS-SP-BS*/
                                  ISIG);  /*Enable SIGINTR, SIGSUSP, SIGDSUSP, and SIGQUIT signals*/

          options.c_cc[VMIN]=0;
          options.c_cc[VTIME]=5; // For half-second timeout


          tcsetattr(fd, TCSANOW, &options); /*Make changes now without waiting for data to complete*/

      }
      return true;
}