Synchronize serial data read from Rfcomm in Qt

I have created a producer-consumer thread system to read data from a serial port /dev/rfcomm0. The producer is calling the serial read function and storing data in a circular buffer. The serial read fucntion also takes care to parse the data and return it in a readable format, which stores it in the circular buffer. The consumer accesses this data from the buffer and calls slots to update a graph.

The data being read from the serial buffer is correct as long as i run the code in debug mode. The breakpoint is set after the serial read function call. But if I execute the program in normal mode, only the first data is read correctly, but subsequent data is garbled. The read buffer has no readable data in it. I do not understand why the serial buffer is not being read correctly.

I'm using Qt 5.3.2 with Qt creator 3.2.1 on Raspberry Pi 3.

My serial read code is as follows:

Code:

int serialReadData (int fd, char * outStr)
{
    char data[23];
    bool flag = true;
    bool valid_data = false;
    int count = 0;
    int i = 0;
    int n = read(fd,&data,23);
 
    if((n == 23) && (data[0] == 's') && (data[1] == 't'))
    {
        for(int i = 0; i < 21; i++)
        {            
            if((data[i+3] != 'e') && (data[i+4] != 'n'))
            {
                outStr[i] = data[i+3];
            }
            else
            {
                outStr[i] = '\n';
                break;
            }
        }
        //serialFlush(fd);
        return 1;
    }
    return 0;
}

My Producer thread is as follows:

Code:

void rxDatafromBT::run()
{
    char readData[DataSize];
    int dataCount = 0;
 
    /*Open serial port connection to read data from /dev/rfcomm0*/
    int fd = serialOpen("/dev/rfcomm0",9600);
 
    /*If serial open not successful, report error and exit the thread*/
    if(fd == -1)
    {
        qDebug("Error Opening Serial Port to /dev/rfcomm \n");
        emit errorOpeningPort();
    }
    /*If successful, then enter into while(1) loop*/
    else
    {
        /*Run this Forever-Until program is terminated*/
        while(!this->isInterruptionRequested()) {
            /*Acquire data here from serial port*/
 
            /*If first byte of data is the correct validity byte
              Copy the data to data buffer, else ignore data*/
           //if((readData != NULL) && (readData[0] == 0x5A))
 
           if(serialReadData(fd,readData))
           {
               freeBytes.acquire();
               for(int i = 0; i < DataSize; i++)
               {
                   if(*(readData + i) == '\n')
                   {
                       break;
                   }
                   buffer[dataCount][i] = *(readData + i);
               }
 
               usedBytes.release();
 
               dataCount++;
               if(dataCount>=BufferSize)
               {
                   dataCount = 0;
               }
           }
 
        }
 
    }
}

Will be gald to accept any help/suggestion to resolve this issue.

Best Regards,
Ksir