Real-time workshop - using external time management

I'm quite new to Matlab/Simulink. I am studying all the documentation but still can not find solution.

I am using Simulink to create a model and Real-Time Workshop to convert it to C++ code. Then, I have to integrate this code automatically generated, within other existing code. I can do it.

The existing C++ code can properly handle the inputs and outputs of the model. To do this I set the storage class of those signals such as ImportedExtern.

But now I need to use in the Simulink model an externally generated clock presented in the existing C++ code. I can do this? I'm trying to understand how time is handled in the simulation and which blocks can be involved.

Perhaps the question has a simple answer, most of what I think. I hope I was clear enough.

Thank you in advance.

Answer 1

[Guy Rouleau]

RTW will generate a "step" function. You just need to use your external clock to call this "step" function in your C/C++ application at the right time.

Typically, you need to call the "step" function at the same rate as the one specified in the model. That way, the "step" function will automatically increase its time internally.

If you want to call the "step" function asynchrounously, or at non-constant intervals, you should ensure that your model is sample time independant, as explained here:

http://www.mathworks.com/help/toolbox/simulink/gui/bq7cmsp-1.html#bq990zm-1

[Luca Goldoni]

Thanks for your reply. But I'm not sure I've correctly understood. RTW generates files including one called model.cpp. Inside that, there is the grt interfaces. Now the external code follows these steps to use the model:

* MdlStart ();

* initializes input signals (I use StorageClass ImportedExtern)

* MdlOutputs ();

* save the outputs of the model in the local varible of the external code

* MdlTerminate ();

I think that the "step" function to call in the interface is indicated as MdlUpdates. Is it? Is what I have to rely on the same frequency of the clock in my existing code?

Is there a way to pass to the model a specific timestep? Or a time variable?

Thanks again.

[Kaustubha Govind]

The step function is generated as rt_OneStep, which you can tie in to your clock. I'm not sure what you mean by passing in a time variable - is this just something that the function must use as any other parameter, or do you want the model to somehow act upon this input by automatically running at the given frequency? AFAIK, the latter is not possible.

Answer 2

[Luca Goldoni]

Thanks for your reply. But I'm not sure I've correctly understood. RTW generates files including one called model.cpp. Inside that, there is the grt interfaces. Now the external code follows these steps to use the model:

• MdlStart ();
• initializes input signals (I use StorageClass ImportedExtern)
• MdlOutputs ();
• save the outputs of the model in the local varible of the external code
• MdlTerminate ();

I think that the "step" function to call in the interface is indicated as MdlUpdates. Is it? Is what I have to rely on the same frequency of the clock in my existing code?

Is there a way to pass to the model a specific timestep? Or a time variable?

Thanks again.