Thread: Wirte and read serial port

Hello guys,i've a code which objective is to send Hex command to the serial port and then wait for 5 second. Then, read data output from the serial port. But my code doesn't works well. Please help me guys. Thanks in advanced.

Code:

 #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.
  */

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

   fd = open("/dev/ttyUSB0", O_RDWR | O_NOCTTY | O_NDELAY);

   if (fd == -1)
   {                                              /* Could not open the port */
     fprintf(stderr, "open_port: Unable to open /dev/ttyUSB0 - %s\n",
             strerror(errno));
   }

   return (fd);
 }

void main()
{
 int mainfd=0,fd;                                            /* File descriptor */
 char chout;
 struct termios options;
   
 mainfd = open_port();

 fcntl(mainfd, F_SETFL, FNDELAY);                  /* Configure port reading */
                                     /* Get the current options for the port */
 tcgetattr(mainfd, &options);
 cfsetispeed(&options, B19200);                 /* Set the baud rates to 19200 */
 cfsetospeed(&options, B19200);
    
                                   /* Enable the receiver and set local mode */
 options.c_cflag |= (CLOCAL | CREAD);
 options.c_cflag &= ~PARENB; /* Mask the character size to 8 bits, no parity */
 options.c_cflag &= ~CSTOPB;
 options.c_cflag &= ~CSIZE;
 options.c_cflag |=  CS8;                              /* Select 8 data bits */
 options.c_cflag &= ~CRTSCTS;               /* Disable hardware flow control */  
 
                                 /* Enable data to be processed as raw input */
 options.c_lflag &= ~(ICANON | ECHO | ISIG);
       
                                        /* Set the new options for the port */
 tcsetattr(mainfd, TCSANOW, &options);

 write(fd,"\xF5\x01\x00\x01\x03\x00\x03\xF5",8);
 
 usleep(5000000);      /* wait for 5 second*/

 read(mainfd, &chout, sizeof(chout));          /* Read character from ABU (Auto buffering Unit) */
   
   if (chout != 0)
      printf("Got %c.\n", chout);

   chout=0;
   
 
                                                    /* Close the serial port */
  close(mainfd);
 }