MATLAB: Can I use the MEX-file generated by the EMLMEX command in an S-function in Simulink 7.4 (R2009b)

embeddedemlemlmexs-functionsimulink

I am using the EMLMEX command to generate a MEX-file. Can I use this MEX-file in an S-function block in Simulink 7.4 (R2009b)?

Best Answer

The ability to use a MEX-file generated by the EMLMEX command in an S-function is unavailable in Simulink 7.4 (R2009b).This is because an S-function MEX-file requires certain callbacks such as mdlInitialize, mdlOutputs, etc. which are not generated by the EMLMEX command.

As a workaround, you may use the Embedded MATLAB block in Simulink for this purpose.

Related Solutions

MATLAB: Are static variables in C or FORTRAN MEX S-functions not reset when running successive simulations

In general, work vectors are recommended over static or global variables if your S-function needs persistent memory storage. For more information on this, see the "Writing S-Functions" manual.

However, if you need to use such variables, you should be aware that C-MEX or FORTRAN S-functions are shared libraries and are not unloaded from memory when a simulation stops. There are multiple workaround to re-initialize these variables in an S-function.

1. You can clear all loaded MEX-functions (this includes but is not limited to S-functions) with the following command:

clear mex

You should run this command between simulations.

2. An alternative is to clear only those MEX-functions that should be unloaded from memory before a simulation because of their static variables. If the function that should be unloaded is mySfunction, you can unload it from memory with:

clear mySfunction

This option is used in the example model testmodel_wo1 and it is entered in the InitFcn callback of this model, such that this is called right before the model is simulated.

3. If you would like to use your custom S-function in various models and do not want to use model-wide callback functions, it is also possible to unload the S-function from memory in a callback specific to the S-function. You can set the following command as the InitFcn callback of the S-function itself:

clear(get_param(gcb, 'FunctionName'))

This option is used in the example model testmodel_wo2.

4. Finally it is also possible to initialize static variables in the S-function itself. In the example model testmodel_wo3, this option is used. For the example models attached to this solution, the Legacy Code Tool is used to generate the S-functions for the example models. For this option the StartFcnSpec is used to specify a C function that will be called at the start of a simulation. This function initializes persistent variables and since it will be called at the start of every simulation as opposed to when the S-function is loaded, it will have the same state for each simulation run.

MATLAB: Does Simulink Accelerator not use all TLC methods even if I use the SS_OPTION_USE_TLC_WITH_ACCELERATOR option in Real-Time Workshop 7.4 (R2009b)

The observed is the expected behavior of Real-Time Workshop 7.4 (R2009b):

 1) Rapid Accelerator: The TLC is being used
 2) Accelerator without SS_OPTION_USE_TLC_WITH_ACCELERATOR: No TLC is used
 3) Accelerator with SS_OPTION_USE_TLC_WITH_ACCELERATOR: Parts of the TLC are being used
    * mdlOutputs()
    * mdlUpdate()
    * mdlDerivatives()

Read below for a more detailed description:

Look at the documentation for a "Process View" of "How the Simulink Engine Interacts with C S-Functions", at

 <http://www.mathworks.com/access/helpdesk/help/toolbox/simulink/sfg/f8-37326.html#f8-83424>

This section of the documentation is about S-Functions, but nearly everything in it applies equally well to all blocks, and to entire models. In Normal mode, running a Model method runs the corresponding Block method for each block in the model. For a subsystem, running a Block method runs the corresponding method for each block in the subsystem.

The Simulink Accelerator generates code for a C-MEX S-Function containing code for the simulation loop of the model. In Accelerator mode, methods in diagram "Model Initialization" run just as they do in Normal mode, but some methods in diagram "Simulation Loop" run differently. Model methods mdlOutputs(), mdlUpdate(), and mdlDerivatives() call the corresponding methods in the Accelerator S-Function, instead of calling the methods for each individual block.

As observed, the Accelerator S-Function does not include the optional mdlStart() and mdlInitializeConditions(). It does contain the required mdlInitializeSampleTimes() and mdlTerminate(), but they are empty functions that are never called. It contains the required mdlInitializeSize(), but it operates differently than in a typical S-Function, checking to see if the S-Function needs to be recreated, and verifying that DWork and BlockIO are the correct size.

If SS_OPTION_USE_TLC_WITH_ACCELERATOR is set in an S-Function, the Accelerator S-Function methods mdlOutputs(), mdlUpdate(), and mdlDerivatives() will contain code generated by the corresponding .tlc file, if it exists. Otherwise the Accelerator S-Function will have code to call the corresponding methods in

the .mex file for the S-Function.

Note that mdlDerivatives() exists only if the model has continuous states.

For both Accelerator and Normal mode, put the desired code for mdlStart() and mdlInitializeConditions() in the S-Function source file and build it into the .mex file

To use mdlStart() and mdlInitializeConditions() code generated by the .tlc file that inlines an S-Function, use Rapid Accelerator or a Real-Time Workshop Target.

Best Answer

Related Solutions

MATLAB: Are static variables in C or FORTRAN MEX S-functions not reset when running successive simulations

MATLAB: Does Simulink Accelerator not use all TLC methods even if I use the SS_OPTION_​USE_TLC_WI​TH_ACCELER​ATOR option in Real-Time Workshop 7.4 (R2009b)

Related Question

MATLAB: Does Simulink Accelerator not use all TLC methods even if I use the SS_OPTION_USE_TLC_WITH_ACCELERATOR option in Real-Time Workshop 7.4 (R2009b)