Visual Studio 2010 Arduino serial communication

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?

Why are you using a separate serial cable for runtime data rather than sending it over the same usb-serial channel you use to download the program? — Chris Stratton
I'm inexperienced with serial communication and didn't realize that I could continue to send data unrelated to the initial programming through the type b usb. Would I first program the Arduino and then run the C++ program, with the C++ writing to the same port that was used to program the arduino? — jalconvolvon
Yes. Just treat it like a serial port. Only catch is you should release the port from your custom program (or quit it) before trying to download a modification to the sketch. Also if you had used an rs232 cable without a level shifter, you may have damaged the arduino with overvoltage. First question would be if it will program with the custom cabling removed and not having run your custom program since boot of the pc. — Chris Stratton
I was able to get it working using your suggestion, thank you! — jalconvolvon

Mitch Mitch · Accepted Answer · 2012-11-25T02:05:16

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);

Visual Studio 2010 Arduino serial communication

1 Answers