[Linux/C] Read 10bytes from Serial Port

    /*=======================================================================*/
        /* Serial Port Programming in C (Serial Port Read)                    */
    /* Non Cannonical mode                                                      */
    /* ----------------------------------------------------------------------*/
        /* Program reads a string from the serial port at 9600 bps 8N1 format */
    /* Baudrate - 9600                                                          */
    /* Stop bits -1                                                             */
    /* No Parity                                                                */
    /* ----------------------------------------------------------------------*/
    /* Compiler/IDE  : gcc 4.6.3                                                */
    /* Library       :                                                          */
    /* Commands      : gcc -o serialport_read serialport_read.c                 */
    /* OS            : Linux(x86) (Linux Mint 13 Maya)(Linux Kernel 3.x.x)      */
    /* Programmer    : Rahul.S                                                  */
    /* Date          : 21-December-2014                                         */
    /*=======================================================================*/

    /*=======================================================================*/
    /* www.xanthium.in                                            */
    /* Copyright (C) 2014 Rahul.S                                               */
    /*=======================================================================*/
    /*=======================================================================*/
    /* Running the executable                                                   */
        /* ----------------------------------------------------------------------*/
    /* 1) Compile the  serialport_read.c  file using gcc on the terminal
                (without quotes)
    */
        /*                                                                    */
    /*  " gcc -o serialport_read serialport_read.c "                            */
    /*                                                                          */
        /* 2) Linux will not allow you to access the serial port
                            from user space,you have to be root.So use
                */
        /*    "sudo" command to execute the compiled binary as super user.    */
        /*                                                                    */
        /*       "sudo ./serialport_read"                                     */
    /*                                                                          */
    /*=======================================================================*/

    /*=======================================================================*/
    /* Sellecting the Serial port Number on Linux                               */
    /* ----------------------------------------------------------------------*/
    /* /dev/ttyUSBx - when using USB to Serial Converter,
            where x can be 0,1,2...etc
    */
    /* /dev/ttySx   - for PC hardware based Serial ports,
            where x can be 0,1,2...etc
    */
  /*=======================================================================*/

    /*-------------------------------------------------------------*/
        /* termios structure -  /usr/include/asm-generic/termbits.h    */
    /* use "man termios" to get more info about  termios structure */
    /*-------------------------------------------------------------*/

        #include <stdio.h>
        #include <fcntl.h>   /* File Control Definitions           */
        #include <termios.h> /* POSIX Terminal Control Definitions */
        #include <unistd.h>  /* UNIX Standard Definitions      */
        #include <errno.h>   /* ERROR Number Definitions           */

            #include <time.h>

    void main(void)
        {
            int fd;/*File Descriptor*/

        printf("\n +----------------------------------+");
        printf("\n |        Serial Port Read          |");
        printf("\n +----------------------------------+");

        /*------------ Opening the Serial Port ------------*/

        /* Change /dev/ttyUSB0 to the one corresponding to your system */

            fd = open("/dev/ttyUSB0",O_RDWR | O_NOCTTY);
                    /* ttyUSB0 is the FT232 based USB2SERIAL Converter   */
                /* O_RDWR   - Read/Write access to serial port       */
                    /* O_NOCTTY - No terminal will control the process   */
                    /* Open in blocking mode,read will wait              */



            if(fd == -1)                        /* Error Checking */
                   printf("\n  Error! in Opening ttyUSB0  ");
            else
                   printf("\n  ttyUSB0 Opened Successfully ");


        /*---------- Setting the Attributes of the serial port using termios structure --------- */

        struct termios SerialPortSettings;  /* Create the structure                          */

        tcgetattr(fd, &SerialPortSettings); /* Get the current attributes of the Serial port */

        /* Setting the Baud rate */
        cfsetispeed(&SerialPortSettings,B9600); /* Set Read  Speed as 9600                       */
        cfsetospeed(&SerialPortSettings,B9600); /* Set Write Speed as 9600                       */

        /* 8N1 Mode */
        SerialPortSettings.c_cflag &= ~PARENB;      /* Disables the Parity Enable bit(PARENB),So No Parity   */
        SerialPortSettings.c_cflag &= ~CSTOPB;      /* CSTOPB = 2 Stop bits,here it is cleared so 1 Stop bit */
        SerialPortSettings.c_cflag &= ~CSIZE;           /* Clears the mask for setting the data size             */
        SerialPortSettings.c_cflag |=  CS8;         /* Set the data bits = 8                                 */

        SerialPortSettings.c_cflag &= ~CRTSCTS;       /* No Hardware flow Control                         */
        SerialPortSettings.c_cflag |= CREAD | CLOCAL; /* Enable receiver,Ignore Modem Control lines       */


        SerialPortSettings.c_iflag &= ~(IXON | IXOFF | IXANY);          /* Disable XON/XOFF flow control both i/p and o/p */
        SerialPortSettings.c_iflag &= ~(ICANON | ECHO | ECHOE | ISIG);  /* Non Cannonical mode                            */

        SerialPortSettings.c_oflag &= ~OPOST;/*No Output Processing*/

        /* Setting Time outs */
        SerialPortSettings.c_cc[VMIN] = 10; /* Read at least 10 characters */
        SerialPortSettings.c_cc[VTIME] = 0; /* Wait indefinetly   */
        /* http://www.unixwiz.net/techtips/termios-vmin-vtime.html
         * Helped me to figure out some things...
         */


        if((tcsetattr(fd,TCSANOW,&SerialPortSettings)) != 0) /* Set the attributes to the termios structure*/
            printf("\n  ERROR ! in Setting attributes");
        else
            printf("\n  BaudRate = 9600 \n  StopBits = 1 \n  Parity   = none");

            /*------------------------------- Read data from serial port -----------------------------*/

        // tcflush(fd, TCIFLUSH);   /* Discards old data in the rx buffer            */
    //
        // char read_buffer[10];   /* Buffer to store the data received              */
        // int  bytes_read = 0;    /* Number of bytes read by the read() system call */
        // int i = 0;
    //
        // clock_t start = clock();
        // bytes_read = read(fd,&read_buffer,10); /* Read the data                   */
        // clock_t stop = clock();
    //
        // double elapsed = (double)(stop - start) * 1000.0 / CLOCKS_PER_SEC;
        // printf("\n  Time elapsed in ms: %f", elapsed);
    //
        // printf("\n\n  Bytes Rxed -%d", bytes_read); /* Print the number of bytes read */
        // printf("\n\n  ");
    //
        // start = clock();
        // for(i=0;i<bytes_read;i++)     /*printing only the received characters*/
        //     printf("%c",read_buffer[i]);
        // stop = clock();
    //
        // elapsed = (double)(stop - start) * 1000.0 / CLOCKS_PER_SEC;
        // printf("\n  Time elapsed in ms: %f", elapsed);
    //
    //
        // printf("\n +----------------------------------+\n\n\n");


        /* PLEASE NOTE:
         * If you try transfer only 10 characters, it seems like its very slow
         * but once you set it to receive them continiously they arrive at they
         * expected rate. So, only first transfer takes longer...
         */

        char read_buffer[10];   /* Buffer to store the data received              */
        int  bytes_read = 0;    /* Number of bytes read by the read() system call */
        int i = 0;

        while(1) {
            tcflush(fd, TCIFLUSH);   /* Discards old data in the rx buffer            */
            bytes_read = read(fd,&read_buffer,10); /* Read the data                   */

          printf("\n ");

            for(i=0;i<bytes_read;i++)    /*printing only the received characters*/
                printf("%c",read_buffer[i]);
            printf("\n +----------------------------------+\n\n\n");
        }

        close(fd); /* Close the serial port */

}