question

I'm trying to read engine RPM in a Cassna 152. After trying a multitude of ways to read a SimVar, I ended with Lockheed's sample and tweaked it (like changing the read interval to Frames).

{ I isolated my SimConnect code to separate .h file cause I use a USB code generator for my PIC and C++ code, and it rewrites over the C++ program. That way I have very little modifications to re-do each time I change my USB code. }

I trigger the CallBack from a Button control for the time being, it will be moved into a Timer later.

private: System::Void MainForm_Load(System::Object^ sender, System::EventArgs^ e)
{
    OpenSimConnect();
}

private: System::Void bUpdateIndicators_Click(System::Object^ sender, System::EventArgs^ e)
{
    SimConnect_CallDispatch(hSimConnect, MyDispatchProcPDR, NULL);

//this->tbEngine1_RPM->Text = intEngine1_RPM;
}

private: System::Void bClose_Click(System::Object^ sender, System::EventArgs^ e)
{
    CloseSimConnect();
    Application::Exit();
}

The SimConnect code:

//Copyright (c) Lockheed Martin Corporation.  All rights reserved. 
//------------------------------------------------------------------------------
//
//  SimConnect Tagged Data Request Sample
// 
//    Description:
//                After a flight has loaded, request the vertical speed and pitot
//                heat switch setting of the user aircraft, but only when the data
//                has changed
//------------------------------------------------------------------------------
#pragma once

#include <windows.h>
#include "SimConnect.h"
#include <tchar.h>
#include <stdio.h>
#include <strsafe.h>

int     quit = 0;
HANDLE  hSimConnect = NULL;

// A basic structure for a single item of returned data
struct StructOneDatum {
    int        id;
    float    value;
};

// maxReturnedItems is 3 in this case, as the sample only requests RPM,
// vertical speed and pitot heat switch data
#define maxReturnedItems    3

// A structure that can be used to receive Tagged data
struct StructDatum {
    StructOneDatum  datum[maxReturnedItems];
};

static enum EVENT_PDR {
    EVENT_SIM_START,
};

static enum DATA_DEFINE_ID {
    DEFINITION_PDR,
};

static enum DATA_REQUEST_ID {
    REQUEST_PDR,
};

static enum DATA_NAMES {
    DATA_ENGINE1_RPM,
    DATA_VERTICAL_SPEED,
    DATA_PITOT_HEAT,
};

void OpenSimConnect()
{
    HRESULT hr;

    if (SUCCEEDED(SimConnect_Open(&hSimConnect, "Open", NULL, 0, 0, 0)))
    {
        hr = SimConnect_AddToDataDefinition(hSimConnect, DEFINITION_PDR, "PROP RPM:1", "rpm",
            SIMCONNECT_DATATYPE_FLOAT32, 0, DATA_ENGINE1_RPM);

        hr = SimConnect_AddToDataDefinition(hSimConnect, DEFINITION_PDR, "Vertical Speed", "Feet per second",
            SIMCONNECT_DATATYPE_FLOAT32, 0, DATA_VERTICAL_SPEED);

        hr = SimConnect_AddToDataDefinition(hSimConnect, DEFINITION_PDR, "Pitot Heat", "Bool",
            SIMCONNECT_DATATYPE_FLOAT32, 0, DATA_PITOT_HEAT);

        hr = SimConnect_RequestDataOnSimObject(hSimConnect, REQUEST_PDR, DEFINITION_PDR,
            SIMCONNECT_OBJECT_ID_USER, SIMCONNECT_PERIOD_VISUAL_FRAME, 0, 0);
    }
}

void CloseSimConnect()
{
    HRESULT hr;
    hr = SimConnect_Close(hSimConnect);
}

void CALLBACK MyDispatchProcPDR(SIMCONNECT_RECV* pData, DWORD cbData, void* pContext)
{
    HRESULT hr;

    float fltEngine1_RPM;

    switch (pData->dwID)
    {
        case SIMCONNECT_RECV_ID_SIMOBJECT_DATA:
        {
            SIMCONNECT_RECV_SIMOBJECT_DATA* pObjData = (SIMCONNECT_RECV_SIMOBJECT_DATA*)pData;

            switch (pObjData->dwRequestID)
            {
                case REQUEST_PDR:
                {
                    int    count = 0;;
                    StructDatum* pS = (StructDatum*)&pObjData->dwData;

            // There can be a minimum of 1 and a maximum of maxReturnedItems
            // in the StructDatum structure. The actual number returned will
            // be held in the dwDefineCount parameter.

                    while (count < (int)pObjData->dwDefineCount)
                    {
                        switch (pS->datum[count].id)
                        {
                            case DATA_ENGINE1_RPM:
                                // printf("\nEngine 1 RPM = %f", pS->datum[count].value);
                                fltEngine1_RPM = pS->datum[count].value;
                                break;

                            case DATA_VERTICAL_SPEED:
                                // printf("\nVertical speed = %f", pS->datum[count].value);
                                break;

                            case DATA_PITOT_HEAT:
                                // printf("\nPitot heat = %f", pS->datum[count].value);
                                break;

                            default:
                                // printf("\nUnknown datum ID: %d", pS->datum[count].id);
                                break;
                        }
                        ++count;
                    }
                    break;
                }
                default:
                break;
            }
            break;
        }
    }
}

I added Engine1 RPM for my application. I get weird data when I add a Breakpoint at where "I think" Engine 1 RPM is read.


I'm a main-frame programmer by trade, so please disregard my ignorance when it comes to coding C++ and using structures and variables properly in C++ (I only started C++ this year on my own).

My goal is to get that Engine 1 RPM into a variable that I can handle, like displaying on-screen, but the main goal is to move to USB variables for download to a PIC mcu.

Thanks for any help!

Robert