RTDLL Sample

This example program demonstrates how to use an RTDLL in an RTSS Process. It uses library functionality to provide an application similar to the DLL sample.

This sample includes three components:

A shared RTDLL (SampleRtdll.Rtdll) that defines the exported function.
An application that explicitly loads the RTDLL at runtime.
An application that implicitly links against the RTDLL at build time.

Source Files

The Rtdll example includes three projects, available from the VS<Visual Studio Version> folder:

File	Description
`SampleRtDll_<Visual Studio version>.vcxproj`	Builds `SampleRtdll.Rtdll`. This is an RTDLL that contains the function Toggle which toggles the state of the speaker.
`ExplicitLoadRtdll_<Visual Studio version>.vcproj`	Builds `ExplicitLoadRtdll.c`. This loads an RTDLL, calls an RTDLL function, and then frees the RTDLL. It can be built as either a Win32 .EXE binary, or an .RTSS binary.
`ImplicitLoadRtdll_<Visual Studio version>.vcproj`	Builds `ImplicitLinkdll.c`. This is compiled with the project settings the `.rtdll` is linked in. Through an import command, we define the toggle function and run the toggle through the RTSS we just called.

The Source folder contains three source files:

File	Description
`explicitlyUsingRtdll.c`	Source file that loads an RTDLL, calls an RTDLL function, and then frees the RTDLL. It can be built as either a Win32 .exe binary, or an .rtss binary.
`implicitlyUsingRtdll.c`	Source file that is compiled with the project settings the `.rtdll` is linked in, then through an import command we define the toggle function and run the toggle through the RTSS we just called.
`sampleRtdll.c`	Source file for an RTDLL that contains the function "Toggle" which toggles the state of the speaker.

Building the Sample

Build the three samples using any of the four available configurations: Debug, Release, RTSSDebug, or RTSSRelease.

SampleRtdll.Rtdll is placed in the same directory as ExplicitLoadRTDLL.rtss and ImplicitLinkRTDLL.rtss
The .lib file generated by the RTDLL project is linked in the implicit loader's project settings.

Running the Sample

Run the explicit loader binary:

RTSSrun explicitLoadRTDLL.rtss

Alternatively, you can run the implicit loader binary:

RTSSrun ImplicitLinkRTDLL.rtss

The shared library function Toggle is called repeatedly through a periodic RTAPI timer for 10 seconds in both versions.

Expected Results

Logs are generated from the DLL lifecycle (DllMain) such as PROCESS_ATTACH and PROCESS_DETACH.
Console messages confirm success or failure when loading or unloading the RTDLL.
The explicitly loaded version reports any failure to locate the DLL or the Toggle function.

Unexpected Results

The sample fails to find or load the required RTDLL library (it must be in the same directory as the executable).

Remarks

The Toggle function manipulates the PC speaker’s state by directly toggling the GATE_BIT on I/O port 0x61.
In the explicit version:
The RTDLL is loaded at runtime with LoadLibrary, and the function is called via GetProcAddress.
The DLL is released afterward using FreeLibrary.
In the implicit version:
The RTDLL is linked at build time.
The Toggle function is declared with __declspec(dllimport) and called directly.
Both use an RTAPI timer to invoke Toggle repeatedly every 1 ms for 10 seconds.

APIs Referenced

RTAPI	Windows Supported
RtCreateTimer RtDeleteTimer RtReadPortUchar RtSetTimerRelative RtWritePortUchar	FreeLibrary GetProcAddress LoadLibrary