#include<stdio.h>
#include<sys/types.h>
#include<sys/stat.h>
#include<fcntl.h>
#include<unistd.h>
#include<termios.h>
#include<sys/ioctl.h>
#include<sys/time.h>
#include<signal.h>

#define BAUD B115200

int fd0;
int fd1;

dirswitch (int d)
{
  static int direction = -1;
  static int cnt = 0;

  if ((direction == d) && (cnt != 17))
    {
      cnt++;
      return;
    }

  printf ("\n");
  fflush (stdout);

  switch (direction = d)
    {
    case 0:
      printf (">");
      break;
    case 1:
      printf ("<");
      break;
    }
  cnt = 1;

}

static int
mainloop ()
{
  fd_set rfds;
  struct timeval tv;
  unsigned char c;
  int n = (fd0 > fd1) ? (fd0 + 1) : (fd1 + 1);

  while (1)
    {
      tv.tv_sec = 0;
      tv.tv_usec = 500000;

      FD_ZERO (&rfds);
      FD_SET (fd0, &rfds);
      FD_SET (fd1, &rfds);

      if (!select (n, &rfds, NULL, NULL, &tv))
        {
          dirswitch (-1);
          printf (" .");
          fflush (stdout);
        }
      else
        {

          if (FD_ISSET (fd0, &rfds))
            {
              dirswitch (0);
              read (fd0, &c, 1);
              write (fd1, &c, 1);
              printf (" %02X", c);
            }

          if (FD_ISSET (fd1, &rfds))
            {
              dirswitch (1);
              read (fd1, &c, 1);
              write (fd0, &c, 1);
              printf (" %02X", c);
            }


        }

    }

}

static int
init_comms (int fd)
{
  struct termios tios;
  unsigned char buf[0x100];
  int length;

  tcgetattr (fd, &tios);
  tios.c_cflag &= ~(CSIZE | CSTOPB | PARENB | CLOCAL | CRTSCTS);
  tios.c_cflag |= CLOCAL;
  tios.c_cflag |= CS8;

  tios.c_cflag |= CREAD | HUPCL;
  tios.c_iflag = IGNBRK | IGNPAR;

  tios.c_oflag = 0;
  tios.c_lflag = 0;
  tios.c_cc[VMIN] = 1;
  tios.c_cc[VTIME] = 0;


  cfsetospeed (&tios, BAUD);
  cfsetispeed (&tios, BAUD);

  if (tcsetattr (fd, TCSAFLUSH, &tios) < 0)
    return 0;

  return 0;
}

int
open_port (char *port)
{
  int fd;
  fd = open (port, O_RDWR);

  if (fd < 0)
    {
      return -1;
    }

  if (init_comms (fd))
    {
      close (fd);
      return -1;
    }
  return fd;

}

main ()
{
  fd0 = open_port ("/dev/ttyS0");
  fd1 = open_port ("/dev/ttyS1");

  mainloop ();
}