#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <termios.h>
#include <string.h>
#include <unistd.h>
#include <stdio.h>

#define BAUDRATE B9600
#define MODEMDEVICE "/dev/ttyS1"
#define _POSIX_SOURCE 1 /* POSIX compliant source */
#define FALSE 0
#define TRUE 1

main(int argc, char* argv[])
{
  int fd,c, res;
  struct termios oldtio,newtio;
  unsigned char buf;


  buf = argv[1][0];
 fd = open(MODEMDEVICE, O_RDWR | O_NOCTTY|O_NDELAY ); 
 if (fd <0) {perror(MODEMDEVICE); exit(-1); }

 bzero(&newtio, sizeof(newtio));
 tcgetattr(fd,&oldtio); /* save current port settings */
 cfsetispeed(&newtio, B9600);
 cfsetospeed(&newtio, B9600);
 newtio.c_cflag &= ~CSIZE; /* Mask the character size bits */
 newtio.c_cflag |= CS8;    /* Select 8 data bits */

 /* no parity */
 newtio.c_cflag &= ~PARENB;
 newtio.c_cflag &= ~CSTOPB;
 newtio.c_cflag &= ~CSIZE;
 newtio.c_cflag &= ~CRTSCTS;
 newtio.c_cflag |= CS8;
 newtio.c_cflag |=  (CLOCAL| CREAD);
 newtio.c_oflag = 0;

 /* set input mode (non-canonical, no echo,...) */
 newtio.c_lflag = 0;
 
 newtio.c_cc[VTIME]    = 0;   /* inter-character timer unused */
 newtio.c_cc[VMIN]     = 1;   /* blocking read until 5 chars received */

 tcflush(fd, TCIFLUSH);
 tcsetattr(fd,TCSANOW,&newtio);

   res = write(fd,&buf,1);   /* returns after 5 chars have been input */
   printf("wrote %c\n", buf);
}