#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <fcntl.h>
#include <signal.h>
#include <sys/types.h>
#include <sys/termios.h>
#include <sys/time.h>


int
main(int argc, char *argv[])
{
  int ser_fd;

  ser_fd = open("/dev/ttyS0", O_RDWR); // | O_NONBLOCK);

  if (ser_fd == -1)
    {
      perror("open failed");
      exit(-1);
    }


  struct termios term_p;

  tcgetattr(ser_fd, &term_p);

  cfsetispeed(&term_p, B115200);
  cfsetospeed(&term_p, B115200);

  term_p.c_cflag &= ~PARENB;
  term_p.c_cflag &= ~CSTOPB;
  //  term_p.c_cflag &= ~CSIZE;
  term_p.c_cflag |= CS8;
  term_p.c_cflag |= CREAD;

  if (tcsetattr(ser_fd, TCSANOW, &term_p) == -1)
    {
      perror("tcsetattr failed");
      exit(-1);
    }


  fprintf(stdout, "writing ... \n");
  char* message = "Hello World";
  int nwritten = write(ser_fd, message, strlen(message));
  if (nwritten == -1)
    {
      perror("write failed");
      exit(-1);
    }
  fprintf(stdout, "write ok\n");

  fprintf(stdout, "reading ... \n");
  char buf[1024];
  int nread = read(ser_fd, buf, 1024);
  if (nread == -1)
    {
      perror("read failed");
      exit(-1);
    }
  else
    {
      fprintf(stdout, "read %d bytes\n", nread);
    }
  fprintf(stdout, "read ok\n");

  return 0;
}