#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.
 */

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

  fd = open_port();

  // Read the configureation of the port 

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

  /* SEt Baud Rate */

  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;

  // 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;

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

  fcntl(fd, F_SETFL, FNDELAY);


  // Write some stuff !!!

  n = write(fd, "ATZ\r", 4);
  if (n < 0)
    fputs("write() of 4 bytes failed!\n", stderr);
  else
    printf ("Write succeed n = %i\n", n );

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

  char *buf;

  n = read( fd, buf, 1 );

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

  printf ( "Number of bytes to be read = %i\n", n );
  printf ( "Buf = %s\n", buf );

  close( fd );

}

      

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

  fd = open("/dev/tty.KeySerial1", O_RDWR | O_NOCTTY | O_NDELAY);
  if (fd == -1)
    {
      /*
       * Could not open the port.
       */

      perror("open_port: Unable to open /dev/ttyS0 - ");
    }
  else
    fcntl(fd, F_SETFL, FNDELAY);

  printf ( "In Open port fd = %i\n", fd);

  return (fd);
}