MATLAB: Unexpected code generated when subsystem is changed to atomic

coderpointssignalsignalssimulinksimulink codertestvirtual

In my model, I set two signals as test points. When I proceed to generate code, the code is as expected. When I change one of the subsystems in the model to 'Atomic', I seem to observe some extraneous code generated (see below). Why does this happen?

Best Answer

The C-API generates code for all signals, not just test points. The reason you are seeing new signals appear is because when the subsystem is made atomic, some signals that were previously virtual become non-virtual and thus show up in the C-API. For more information on Virtual signals, please review the following documentation page: https://www.mathworks.com/help/simulink/ug/virtual-signals.html

However, these signals will not appear when generating code using Embedded Coder as it employs optimizations not available in Simulink Coder to make the generated code more efficient. Consider using Embedded Coder if the aim is to eliminate these extraneous signals.

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MATLAB: Do the names of particular signals not appear in the “rtBlockSignals” structure generated by Real-Time Workshop 6.0 (R14)

The signal names do not appear in the "rtBlockSignals" structure of the model_capi.c file generated by Real-Time Workshop 6.0 (R14) because SIMULINK cannot propagate signal labels back across virtual subsystem boundaries.

To work around this issue, label the source of the signal within the virtual subsystem boundary. SIMULINK can propagate signal labels forward across virtual subsystem boundaries, such that the output of a Subsystem block shares the same label as the output of the signal source. For example, labeling the output of a Gain block as "my_output" within the Subsystem and appropriately setting its storage class will generate code similar to the following:

 /* Block output signal information */
 static const rtwCAPI_Signals rtBlockSignals[] = {
   /* addrMapIndex, sysNum, blockPath,
    * signalLabel, portNumber, dataTypeIndex, dimIndex, fxpIndex,
 sampTimeIndex
    */
   {0, 0, "testme/Subsystem/Gain",
     "my_output", 0, 0, 0, 0, 0},
   {
     0, 0, NULL, NULL, 0, 0, 0, 0, 0
   }
 };

MATLAB: How to find best practices for modeling buses for simulation and code generation using Real-Time Workshop Embedded Coder

A document on best practices for modeling buses for simulation and code generation can be found at the link below. Basic guidelines covers topics such as bus diagnostics, virtual buses, multi-rate buses, setting the initial value of bus signals, extracting non-virtual bus signals inside atomic subsystems, virtual bus signals crossing atomic boundaries, and arrays in buses. Advanced topics include initializing data with persistent information, working with bus arrays and reusable subsystems, and building bus arrays in reusable subsystems.

http://www.mathworks.com/matlabcentral/fileexchange/23480

Note that MathWorks does not guarantee or warrant the use or content of MATLAB Central submissions. Any questions, issues, or complaints should be directed to the contributing author.

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MATLAB: Do the names of particular signals not appear in the “rtBlockSignals” structure generated by Real-Time Workshop 6.0 (R14)

MATLAB: How to find best practices for modeling buses for simulation and code generation using Real-Time Workshop Embedded Coder

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