Written by Dana Kirsch and Solomon Assefa

#include <stdio.h>
#include <sys/file.h>
#include <sys/time.h>
#include <sys/fcntl.h>
#include <sys/ioctl.h>
#include <sys/types.h>
#include <termios.h>
#include <sys/uio.h>
#include <unistd.h>
#include <errno.h>
#include <ctype.h>
#include <malloc.h>

int OpenPort() {
  struct termios t;
  int fd= open("/dev/cua1", O_RDWR);

  if (fd < 0) {
    perror("opening com1 port");
  } else {
    tcgetattr(fd, &t);
    cfsetispeed(&t, B2400);
    cfsetospeed(&t, B2400);
    cfmakeraw(&t);
    tcsetattr(fd, TCSANOW, &t);
  } return(fd);
}

void main(int argc, char *argv[]) {
  int port; 
  int out;

  port = OpenPort();

  switch (argc) {
  case 1: 
    perror("You need to put an argument");
    break;
  case 2:
    out = atoi(argv[1]); 
    if ((2 <= out) && (out < 10))  {
      /* 0 and VALUES 2 through 9 ONLY VALID !!!! */
      write(port, &out, 1);  
      printf(" %d \n", out); 
      break;
    } perror("not valid, try again");
    break;
  default:
    perror("You have too many arguments");
  }
}