UNIX serial port won't transmit data to BS2 till after port is close

I'm trying to establish 2 way communication between my mac and the basic stamp using unix system calls to open() write() and read(). I'm using the USB BOE to transmit the data to my computer. I have had success doing the reads and writes separately but not at the same time. I would open and get a file descriptor to the device and set all the proper flags for the file descriptor but when ever I write to /dev/tty.usbserial-A4002X2A at 9600, the basic stamp doesn't actually receive the data until I close the file descriptor. I know this because I have the stamp light up an LED when it receives a byte of data through SERIN, not to mention I can see that the blue data received LED on the board iself doesn't light up until I close the connection. And because opening a new serial port connection resets the stamp, I can't open a new connection to read the reply message. Therefore it is impossible for me to send it a message and try to read it's response. I was thinking that there is some hardware buffer that isn't transmitting data until I do a close(fd) and I can't seem to find out how or why. I have even gone as far as trying to use tcflush() or ioctl() but I can't get it to work. Any suggestions or advice for a hopelessly lost fellow BS2 user? Here is my C code:

    int fileDescriptor = -1;
    struct termios options;
    const char *deviceFilePath = "/Dev/tty.usbserial-A4002X2A";
    
   fileDescriptor = open(deviceFilePath, O_RDWR | O_NOCTTY | O_NDELAY);

    if (fileDescriptor == -1)
    {
        printf("Error opening serial port %s - %s(%d).\n",
               deviceFilePath, strerror(errno), errno);
        goto error;
    }
    

    if (fcntl(fileDescriptor, F_SETFL, 0) == -1)
    {
        printf("Error clearing O_NONBLOCK %s - %s(%d).\n",
            deviceFilePath, strerror(errno), errno);
        goto error;
    }

    if (tcgetattr(fileDescriptor, &options) == -1)
    {
        printf("Error getting tty attributes %s - %s(%d).\n",
            deviceFilePath, strerror(errno), errno);
        goto error;
    }
    
    cfsetispeed(&options, B9600);
    cfsetospeed(&options, B9600);
    
    //using raw input
    options.c_lflag &= ~(ICANON | ECHO | ECHOE | ISIG);
    
    //set character size and control flow
    options.c_cflag |= (CS8 |    // Use 8 bit words
            CCTS_OFLOW |        // CTS flow control of output    <-----PROBLEM HERE DON'T SET HARDWARE CONTROL FLOW
            CRTS_IFLOW);        // RTS flow control of input  <-----PROBLEM HERE DON'T SET HARDWARE CONTROL FLOW
                                
            
    //no parity
    options.c_cflag &= ~PARENB;
    options.c_cflag &= ~CSTOPB;
    options.c_cflag &= ~CSIZE;
    
    //Enable the receiver and set local mode...
    options.c_cflag |= (CLOCAL | CREAD);
            
    //disable software flow control
    //options.c_iflag &= ~(IXON | IXOFF | IXANY);
    
    // Cause the new options to take effect immediately.
    if (tcsetattr(fileDescriptor, TCSANOW, &options) == -1)
    {
        printf("Error setting tty attributes %s - %s(%d).\n",
            deviceFilePath, strerror(errno), errno);
        goto error;
    }
    
    
    char writeBuf1[noparse][[/noparse]] = "2";
    int written;
        
    if((written = write(fileDescriptor, writeBuf1, 1)) == -1)
    {
            printf("Error writing data - %s(%d).\n", strerror(errno), errno);
            goto error;
        }
    
    printf("\nBytes written: %d\n",written);
    printf("\nDone writing data...\n");
        
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
program on the stamp hasn't received any data at this point so I can't try to read a reply message 
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
    close(fileDescriptor);

Post Edited (collegekid1) : 5/24/2008 7:33:28 PM GMT