Visual Studio 2010 Arduino serial communication - winapi

Question

I am using OpenCV in Visual Studio 2010 to track an object, and I am trying to send a value to the Arduino to rotate servos attached to the camera. I am using an Arduino Uno. I have completed the C++ code that tracks the object and determines which direction the camera needs to be rotated, but I am having trouble sending this data to the Arduino. I am currently trying to use an RS-232 cable for this. I am using a Type-B USB cable to program my Arduino and an RS-232 to try to send the data from Visual Studio to the Arduino. Here is my code for the Visual Studio serial communication:
int portspeed(int centerpix, int xmid)
{HANDLE hDevice = CreateFile(L"COM5",GENERIC_READ | GENERIC_WRITE,FILE_SHARE_READ | FILE_SHARE_WRITE,NULL,OPEN_EXISTING,0,0);
DCB lpTest;
GetCommState(hDevice,&lpTest);
lpTest.BaudRate = CBR_9600;
lpTest.ByteSize = 8;
lpTest.Parity = NOPARITY;
lpTest.StopBits = ONESTOPBIT;
SetCommState(hDevice,&lpTest);
DWORD btsIO;
if (centerpix<xmid)
{
char test[] = "2";
WriteFile(hDevice,test,strlen(test),&btsIO,NULL);
cout << "Turn right " << test << endl;
}
else
{
char test[] = "3";
WriteFile(hDevice,test,strlen(test),&btsIO,NULL);
cout << "Turn left " << test << endl;
}
return 0;
}
On the Arduino code side I have this, which I am using to attempt to light two different LEDS to see if the program is able to correctly communicate which direction it needs to rotate:
int incomingByte = 0; // For incoming serial data
void setup()
{
Serial.begin(9600); // Opens serial port, sets data rate to 9600 bit/s
}
void loop()
{
// Send data only when you receive data:
if (Serial.available() > 0)
{
incomingByte = Serial.read();
if (incomingByte==50) //if =2
analogWrite(9,100);
else
analogWrite(9,0);
if (incomingByte==51) //if =3
analogWrite(10,50);
else analogWrite(10,0);
delay(3000);
}
else
analogWrite(9,255);
}
My interpretation is that I need to start the C++ program (which continuously sends the data over the serial communication), and then attach the TX pin from the RS-232 into the RX pin (digital 0) on the Arduino. When I try to upload the program to the Arduino I am given an error,
avrdude: stk500_getsync(): not in sync: resp=0x00
This only occurs when I have a wire going into the RX pin, even if this wire is not connected to anything. I believe that this error occurs because the RX is looking for an input with a baud rate of 9600, but it still gives me this error when the C++ program is running and sending the data with a rate of 9600.
How can I send a value from a Visual Studio project doing real time image processing on a laptop to an Arduino via serial communication?

Answer 1

Speaking as someone with limited Win32 experience (more of a .NET guy, really), I think your problem may be in write buffering.
By default, writes to a file or port are buffered in memory. Perhaps the write is never getting sent to the port as you are never closing the file handle nor calling [FlushFileBuffers][3].
Try adding this prior to return 0;:
//After a time, sensitive write
FlushFileBuffers(hDevice);
//or, more properly for the end of the program.
CloseHandle(hDevice);