#include <stdio.h>   /* Standard input/output definitions */
#include <string.h>  /* String function definitions */
#include <unistd.h>  /* UNIX standard function definitions */
#include <fcntl.h>   /* File control definitions */
#include <errno.h>   /* Error number definitions */
#include <termios.h> /* POSIX terminal control definitions */

/*
 * 'open_port()' - Open serial port 1.
 *
 * Returns the file descriptor on success or -1 on error.
 */

int main()
{
      int fd;  // File descriptor
      int n;

      char buf;
      fd = open_port();

      // Read the configureation of the port

      struct termios options;
      tcgetattr( fd, &options );

      /* SEt Baud Rate */

      //cfsetispeed( &options, 2764800 );
      //cfsetospeed( &options, 2764800 );
        cfsetispeed( &options, B9600 );
        cfsetospeed( &options, B9600 );
      //I don't know what this is exactly



      options.c_cflag |= ( CLOCAL | CREAD );

      // Set the Charactor size

      options.c_cflag &= ~CSIZE; /* Mask the character size bits */
      options.c_cflag |= CS8;    /* Select 8 data bits */

      // Set parity - No Parity (8N1)

      options.c_cflag &= ~PARENB;
      options.c_cflag &= ~CSTOPB;
      options.c_cflag &= ~CSIZE;
      options.c_cflag |= CS8;

      //options.c_lflag |= CRTSCTS;
      // Disable Hardware flowcontrol

      //  options.c_cflag &= ~CNEW_RTSCTS;  -- not supported

      // Enable Raw Input

      options.c_lflag &= ~(ICANON | ECHO | ECHOE | ISIG);

      // Disable Software Flow control

      options.c_iflag &= ~(IXON | IXOFF | IXANY);

      // Chose raw (not processed) output

      options.c_oflag &= ~OPOST;

    /* set input mode (non-canonical, no echo,...) */
          //options.c_lflag = 0;

          options.c_cc[VTIME]    = 0;   /* inter-character timer unused */

          options.c_cc[VMIN]     = 1;   /* blocking read until 1 chars received */


      if ( tcsetattr( fd, TCSANOW, &options ) == -1 )
        printf ("Error with tcsetattr = %sn", strerror ( errno ) );
      else
        printf ( "%sn", "tcsetattr succeed" );

      fcntl(fd, F_SETFL, FNDELAY);



      // Write some stuff !!!

      n = write(fd, "ATZATZr", 7);
      if (n < 0)
        fputs("write() of 7 bytes failed!n", stderr);
      else
        printf ("Write succeed n = %in", n );

      /*for ( n = 0 ; n < 1000 ; n++)
        {
          n++;
          n--;
        }
        */

     sleep(12);


      n = read( fd, &buf, 1 );

      if ( n == -1 )
          printf ( "Error = %sn", strerror( errno ) );

      printf ( "Number of bytes to be read = %in", n );
      printf ( "Buf = %cn", buf );

      close( fd );

      return(0);

}



    int open_port(void)
    {
      int fd; /* File descriptor for the port */

      fd = open("/dev/ttyXR0", O_RDWR | O_NOCTTY | O_NDELAY);
      if (fd == -1)
        {
            /*
         * Could not open the port.
             */

          perror("open_port: Unable to open /dev/ttyXR0 - ");
        }
     else
         {
        fcntl(fd, F_SETFL, FNDELAY);
        printf("opening of device /dev/ttyXR0 succeeded !!n");
     }

      printf ( "In Open port fd = %in", fd);

      return (fd);
    }