P3D v3 Serial Communication

[scubakobe]

Hi all,

As stated in a previous post, I am just starting out in SimConnect plugin development. With the help of Ron, I have been able to build working plugins. I am interested in serial communication with an external device, and so far I have successfully been able to establish communication from an external device (Arduino in my case) to P3D. I had the Arduino run a simple function, sending values between -1.0 and +1.0 to move the elevator in P3D.

This worked great, besides a glitch now and then with the elevator position.

Using the throttle control example from the SDK, I modified it to include a 6Hz routine:

        case EVENT_6HZ:
        {
            //Get data from the serial connection
            readResult = SerialP->ReadData(incomingData, dataLength);
            incomingData[readResult] = 0;
            float temp = atof(incomingData); //Perform conversion to type float for P3D
            ec.elevatorPosition = temp;
            //Set elevator position
            hr = SimConnect_SetDataOnSimObject(hSimConnect, DEFINITION_ELEVATOR, SIMCONNECT_OBJECT_ID_USER, 0, 0, sizeof(ec.elevatorPosition), &ec.elevatorPosition);

        }
        break;

The serial object, SerialP, is getting the incoming serial data and placing it in a char buffer of size 256. This must then be converted to float and assigned to the elevator position struct.

Now I want to do the opposite - I'm trying to send the elevator data to my Arduino using a WriteData() command (These functions are defined in a header file provided by Arduino). The data is sent every time the elevator position is requested (Once every sim frame).

        case REQUEST_ELEVATOR:
        {
            // Read and set the initial elevator position value
            structElevatorControl *pS = (structElevatorControl*)&pObjData->dwData;

            ec.elevatorPosition = pS->elevatorPosition;
            double outputData= ec.elevatorPosition;
            char outStr[9];//[sizeof(outputData)];
            memcpy(&outStr, &outputData, sizeof(outputData));
            outStr[9] = '\n';
            printf("\nREQUEST_USERID received, elevator = %2.1f", pS->elevatorPosition);
            SerialP->WriteData(outStr, sizeof(outStr));
            Sleep(15);
        }

The problem I'm trying to tackle is taking the double value of the elevator position, placing it into the char buffer and appending a null terminator '\n' to indicate to the Arduino the end of data.

Could anyone suggest a more elegant way of taking the elevator position, which is a double, and placing it into a character array with a null terminator?

As reference, this is the WriteData() function:

bool Serial::WriteData(char *buffer, unsigned int nbChar)
{
    DWORD bytesSend;

    //Try to write the buffer on the Serial port
    if (!WriteFile(this->hSerial, (void *)buffer, nbChar, &bytesSend, 0))
    {
        //In case it don't work get comm error and return false
        ClearCommError(this->hSerial, &this->errors, &this->status);

        return false;
    }
    else
        return true;
}

I appreciate any help!

Kobbe

 

[JB3DG]

you can use 1 byte hex values on your buffer like 0x00 for the \0 (that is your null terminator. \n is new line I believe).