Prepar3d V4 LVAR Change using C++

[Mostafa]

I am trying to change a switch which has LVAR: ASD_SWITCH_EXT_POWER using C++ code, so I am using UIPC_SDK_C_version2.
Could anyone give me a snippet of code on how to read the value of the switch and how to change its value to 1. 
Also trying to build any code using FSUIPC_User64.h results in build error ( The library was created by a different version of the compiler ) is there is something I am missing?
Thanks In Advance.

[John Dowson]

5 hours ago, Mostafa said:

Also trying to build any code using FSUIPC_User64.h results in build error ( The library was created by a different version of the compiler ) is there is something I am missing?

The source is provided so you can recompile it with the latest compiler. However, I did recompile this recently (for FSUIPC7), so I have attached this below.

5 hours ago, Mostafa said:

I am trying to change a switch which has LVAR: ASD_SWITCH_EXT_POWER using C++ code, so I am using UIPC_SDK_C_version2.

Sorry, but I just don't have the time to provide an example. I have never used most of the provided SDKs and they are provided as-is, and most donated by other authors.

You need to first write the new value to a user offset (e.g. 0x66C0) using FSUIPC_Write, then write the offset address used + the value format (as described in the offset status document) to offset 0x0D6C (again, using FSUIPC_Write), and then the lvar write request, which would be "::ASD_SWITCH_EXT_POWER", to offset 0x0D70 (using FSUIPC_Write), and then call FSUIPC_Process to apply.

Note that the only supported SDK is the .Net / C# one provided by Paul Henty - there is a sub-forum for this interface: https://forum.simflight.com/forum/167-fsuipc-client-dll-for-net/

UIPC64_SDK_C_version2.zip

[Mostafa]

Using this code as your instructions just added a FSUIPC_Read function before Close:

 

#include <iostream>
#include <windows.h>
#include "FSUIPC_User64.h"
#include <iomanip>

using namespace std;

int main()
{
    DWORD dwResult;

    if (FSUIPC_Open(SIM_ANY, &dwResult))
    {
        std::cout << "Connected to FSUIPC" << std::endl;

        double newLvarValue = 1.0; // The value you want to set

        // Step 1: Write the new LVAR value to user offset 0x66C0
        if (!FSUIPC_Write(0x66C0, sizeof(newLvarValue), &newLvarValue, &dwResult))
        {
            std::cout << "Failed to write new LVAR value to offset 0x66C0" << std::endl;
        }

        // Step 2: Write the offset address (0x66C0) and format specifier (0 for double) to 0x0D6C
        DWORD param = 0x66C00000; // 0x66C0 offset + format specifier (0 = double)
        if (!FSUIPC_Write(0x0D6C, sizeof(param), &param, &dwResult))
        {
            std::cout << "Failed to write parameter to offset 0x0D6C" << std::endl;
        }

        // Step 3: Write the LVAR command "::ASD_SWITCH_EXT_POWER" to 0x0D70
        const char lvarCommand[] = "::ASD_SWITCH_EXT_POWER";
        if (!FSUIPC_Write(0x0D70, sizeof(lvarCommand), (void*)lvarCommand, &dwResult))
        {
            std::cout << "Failed to write LVAR command to offset 0x0D70" << std::endl;
        }

        // Step 4: Process the writes
        if (!FSUIPC_Process(&dwResult))
        {
            std::cout << "FSUIPC process failed" << std::endl;
        }
        else
        {
            std::cout << "LVAR write command sent successfully" << std::endl;
        }

        // Step 5: Read back the value from 0x66C0 to confirm the change
        double readBackValue = 0.0;
        if (FSUIPC_Read(0x66C0, sizeof(readBackValue), &readBackValue, &dwResult))
        {
            FSUIPC_Process(&dwResult);
            std::cout << "LVAR ASD_SWITCH_EXT_POWER updated to: " << readBackValue << std::endl;
        }
        else
        {
            std::cout << "Failed to read back LVAR value" << std::endl;
        }

        FSUIPC_Close();
    }
    else
    {
        std::cout << "Failed to connect to FSUIPC" << std::endl;
    }
}

 

This results in :
Connected to FSUIPC
LVAR write command sent successfully
LVAR ASD_SWITCH_EXT_POWER updated to: 1

But the switch in the simulator doesn't change, I am sure that the switch named ASD_SWITCH_EXT_POWER as I use SPAD.next to get LVARs. Is there is something I am missing ?
Thanks In Advance. @John Dowson

[John Dowson]

1 hour ago, Mostafa said:

DWORD param = 0x66C00000; // 0x66C0 offset + format specifier (0 = double)

According to the docs, this should be
    DWORD param = 0x066C0
From the docs:

Quote

This offset value only occupies the low 16-bits (LOWORD) of the 32-bit value. The high part specifies the value format. Assuming the offset is ‘nnnn’, the options are:     0x0nnnn for 64-bit double (as before)     0x1nnnn for 32-bit float (FLT)     0x2nnnn for 32-bit signed integer (SD)     0x3nnnn for 32-bit unsigned integer (UD)     0x4nnnn for 16-bit signed integer (SW)     0x5nnnn for 16-bit unsigned integer (UW)     0x6nnnn for 8-bit signed integer (SB)     0x7nnnn for 8-bit unsigned integer (UB)

 

As this lvar looks to only have values 0 & 1, you could also use a boolean/unsigned byte.

You can check/verify that the lvar value is changing by listing the lvars (Add-ons->WASM->List lvars) [specific lvar logging facilities are also provided but probably overkill for this], and you can check that setting/changing the lvar value has the required effect using the Add-ons->WASM->Set Lvar menu item to change the lvar value.

1 hour ago, Mostafa said:

if (FSUIPC_Read(0x66C0, sizeof(readBackValue), &readBackValue, &dwResult))
        {
            FSUIPC_Process(&dwResult);
            std::cout << "LVAR ASD_SWITCH_EXT_POWER updated to: " << readBackValue << std::endl;
        }
        else
        {
            std::cout << "Failed to read back LVAR value" << std::endl;
        }

This will always log "LVAR ASD_SWITCH_EXT_POWER updated to: 1" regardless of the value of the lvar as you are just reading the value from the offset that you wrote the value of 1.0 to. You would need to write a read lvar request to offset 0x0D70 to get the actual value of the lvar.

John

Edited Monday at 08:29 AM by John Dowson
Further info added

[Mostafa]

Thank you for your support. 
This is the code that worked for me:

#include <iostream>
#include <windows.h>
#include "FSUIPC_User64.h"
#include <iomanip>

using namespace std;

int main()
{
    DWORD dwResult;

    if (FSUIPC_Open(SIM_ANY, &dwResult))
    {
        std::cout << "Connected to FSUIPC" << std::endl;

        double newLvarValue = 1.0; // The value you want to set

        // Step 1: Write the new LVAR value to user offset 0x66C0
        if (!FSUIPC_Write(0x66C0, sizeof(newLvarValue), &newLvarValue, &dwResult))
        {
            std::cout << "Failed to write new LVAR value to offset 0x66C0" << std::endl;
        }

        // Step 2: Write the offset address (0x66C0) and format specifier (0 for double) to 0x0D6C
        DWORD param = 0x066C0; // 0x66C0 offset + format specifier (0 = double)
        if (!FSUIPC_Write(0x0D6C, sizeof(param), &param, &dwResult))
        {
            std::cout << "Failed to write parameter to offset 0x0D6C" << std::endl;
        }

        // Step 3: Write the LVAR command "::ASD_SWITCH_EXT_POWER" to 0x0D70
        const char lvarCommand[] = "::ASD_SWITCH_EXT_POWER";
        if (!FSUIPC_Write(0x0D70, sizeof(lvarCommand), (void*)lvarCommand, &dwResult))
        {
            std::cout << "Failed to write LVAR command to offset 0x0D70" << std::endl;
        }

        // Step 4: Process the writes
        if (!FSUIPC_Process(&dwResult))
        {
            std::cout << "FSUIPC process failed" << std::endl;
        }
        else
        {
            std::cout << "LVAR write command sent successfully" << std::endl;
        }

        

        FSUIPC_Close();
    }
    else
    {
        std::cout << "Failed to connect to FSUIPC" << std::endl;
    }
}

Could you help me read an LVAR?
@John Dowson

[John Dowson]

4 minutes ago, Mostafa said:

Could you help me read an LVAR?

Read the documentation! Its the same as a write, but write to offset 0x0D70 with one colon, not two, e.g. ":ASD_SWITCH_EXT_POWER"

Then read the value from the offset you wrote to 0x0D6C (0x66C0 in this case).

John