MATLAB: Does Real-Time Workshop 7.5 (R2010a), not generate a reusable function for the atomic subsystem with variable sized signal input or outputs

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I have a model in which I have marked two identical subsystems as atomic and set to "Reusable Function" for Real-Time Workshop code generation. The input to these subsystems is a variable sized signal. However, I see in the generated code that the code is not generated as a reusable single function, but rather two functions are created. Why?

Best Answer

The ability to create a reusable function from a subsystem with variable signal inputs is not available when the maximum size for the variable signals is different between subsystems in Real-Time Workshop 7.5 (R2010a).

As a workaround, if you are able to force Simulink to see an equal maximum size for the variable sized signals, then the code generation may be able to create a reusable function for the subsystem. The attached examples ("No_reusable_function_generated", and "Force_reuse_var_signals") show how to do this with an extra switch which propagates the maximum size of the signal to the subsystem where the reusable function is desired.

"No_reusable_function_generated.mdl" is not able to generate the reusable function due to this mismatch in maximum variable signal size. "Force_reuse_var_signals.mdl" is able to propegate the same maximum sized signals to the subsystem forcing the same maximum size signal. Be sure to turn on Format -> Port/Signal Display -> Signal Dimensions to observe this behavior.

Related Solutions

MATLAB: How to generate code for masked subsystem such that I can see the its parameters initialized, when using Real Time Workshop 7.6 (R2010b)

You can do following steps to see the subsystem block parameters initialization in your generated code when using Real Time workshop 7.6 (R2010b).

1. When using the masked subsystem block in a simulink model and using a signal name under the mask, if you would like to include the signal name in the generated code perform the following steps:

 a. Right click the signal name under the mask, select 'Signal Properties'.
 b. In the new window, select the Real Time Workshop tab and in the 'Package' option select Simulink. You can select the 'Storage Class' type to SimulinkGlobal.
 c. Save these changes

2. In the top level model window, select the Configuration Parameters. Here you need to uncheck the 'Block Reduction' and 'Inline Parameters' options in the Optimization option.

3. In order to have a single code file generated after the 'Generate Code' step, you need to make changes in the 'Code Placement' settings in the Real Time Workshop option in the 'Configuration Parameters'. In the settings, select the 'compact' option in the 'Code Packaging' option.

4. Build your model after this step.

5. In the generated code, you can see the signal name declared as a variable which is set to a default value in the model initialize block. This value updates when a function call is made such that the variable gets updated.

I have attached a model example 'masking_sample_example.mdl' to this email with all the above settings enabled. You can generate code for this model by using the Ctrl+B shortcut and see the generated code.

MATLAB: Do I not get a reusable function for a subsystem containing a Switch block, when driven by a Constant block using the Real-Time Workshop 6.0 (R14)

This is expected behavior in the Real-Time Workshop 6.0 (R14).

The reason two functions were being generated is because functions that appear reusable at the graphical level may not be reusable at the C-code level especially in the case of Constant values. It is within the Simulink design to generate two functions if the Input/Output signatures vary. In the case of Constant values, Simulink subsystem semantics allow the subsystem to be impacted by its context since the "Switch block" is fed a constant and the value gets hard-coded and not treated as a signal.

In order to reuse a subsystem when the input is an "Inport" block or a "Constant" block, that is, in order to treat the constant block as a signal, use a "Merge" block either within the subsystem or outside the subsystem. The "Merge" block does not create an unnecessary copy of the signal and reuses the memory location of its input and will not add any overhead to the code.

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Related Solutions

MATLAB: How to generate code for masked subsystem such that I can see the its parameters initialized, when using Real Time Workshop 7.6 (R2010b)

MATLAB: Do I not get a reusable function for a subsystem containing a Switch block, when driven by a Constant block using the Real-Time Workshop 6.0 (R14)

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