Problems with Serial port code for Ros

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I wanted the ROS pc to communicate over the UART with a microcontroller on mobile robot, I canot use ros serial as on the controller I canot use C++ code, so I have used a wrapper code for serial port in linux following the example code from this link: https://code.google.com/p/team-diana/...

My code is as follows:

#define DEFAULT_BAUDRATE 115200
#define DEFAULT_SERIALPORT "/dev/ttyUSB0"

//Global data
FILE *fpSerial = NULL;   //serial port file pointer
ros::Publisher ucResponseMsg;
ros::Subscriber ucCommandMsg;
int ucIndex;          //ucontroller index number

int FileDesc;

unsigned char crc_sum=0;

//Initialize serial port, return file descriptor
FILE *serialInit(char * port, int baud)
{
  int BAUD = 0;
  int fd = -1;
  struct termios newtio, oldtio;
  FILE *fp = NULL;

 //Open the serial port as a file descriptor for low level configuration
 // read/write, not controlling terminal for process,
  fd = open(port, O_RDWR | O_NOCTTY | O_NDELAY);

  ROS_INFO("FileDesc : %d",fd);

 if ( fd<0 )
  {
    ROS_ERROR("serialInit: Could not open serial device %s",port);
   return fp;
  }

  // save current serial port settings
  tcgetattr(fd,&oldtio);

  // clear the struct for new port settings
  bzero(&newtio, sizeof(newtio));

  //Look up appropriate baud rate constant
  switch (baud)
  {
     case 38400:
     default:
        BAUD = B38400;
        break;
     case 19200:
        BAUD  = B19200;
        break;
    case 115200:
        BAUD  = B115200;
        break;
     case 9600:
       BAUD  = B9600;
        break;
     case 4800:
        BAUD  = B4800;
        break;
     case 2400:
        BAUD  = B2400;
        break;
     case 1800:
        BAUD  = B1800;
        break;
     case 1200:
        BAUD  = B1200;
        break;
  }  //end of switch baud_rate

  if (cfsetispeed(&newtio, BAUD) < 0 || cfsetospeed(&newtio, BAUD) < 0)
  {
    ROS_ERROR("serialInit: Failed to set serial baud rate: %d", baud);
    close(fd);
    return NULL;
  }

  // set baud rate, (8bit,noparity, 1 stopbit), local control, enable receiving characters.
  newtio.c_cflag  = BAUD | CRTSCTS | CS8 | CLOCAL | CREAD;

  // ignore bytes with parity errors
  newtio.c_iflag =  IGNPAR;

  // raw output
  newtio.c_oflag = 0;

  // set input mode to non - canonical
  newtio.c_lflag = 0;

  // inter-charcter timer 
  newtio.c_cc[VTIME] = 0;

  // blocking read (blocks the read until the no.of charcters are read
  newtio.c_cc[VMIN] = 0;

  // clean the line and activate the settings for the port
  tcflush(fd, TCIFLUSH);
  tcsetattr (fd, TCSANOW,&newtio);

  //Open file as a standard I/O stream
  fp = fdopen(fd, "r+");

 if (!fp) {
    ROS_ERROR("serialInit: Failed to open serial stream %s", port);
    fp = NULL;
  }

ROS_INFO("FileStandard I/O stream: %d",fp);

  return fp;
} //serialInit


//Process ROS command message, send to uController
void ucCommandCallback(const geometry_msgs::TwistConstPtr& cmd_vel)
{
  unsigned char msg[14];
  float test1,test2;
  unsigned long i;

 // build the message packet to be sent
 msg = packet to be sent;
 msg[13] = crc_sum;

   for (i=0;i<14;i++)
   {
     fprintf(fpSerial, "%c", msg[i]);
   }

tcflush(FileDesc, TCOFLUSH); 

} //ucCommandCallback


//Receive command responses from robot uController
//and publish as a ROS message
void *rcvThread(void *arg)
{
  int rcvBufSize = 200;
  char ucResponse[10];//[rcvBufSize];   //response string from uController
  char *bufPos;
  std_msgs::String msg;
  std::stringstream ss;
  int BufPos,i;
  unsigned char crc_rx_sum =0;

  while (ros::ok()) {

     BufPos = fread((void*)ucResponse,1,10,fpSerial);

for (i=0;i<10;i++)
{
 ROS_INFO("T: %x ",(unsigned char)ucResponse[i]);
 ROS_INFO("NT: %x ",ucResponse[i]);
}

          msg.data = ucResponse;
          ucResponseMsg.publish(msg ...