C code generated for variable size model interface

For one of the application, i need to have variable size input to the model. In the actual system the size of data would be changing i.e. either 1, 2,1000 etc. Hence i am trying to use the variable size.

I have changed the inport settings to say that it is a Variable Size. When i generate the c code with Embedded Coder, i see that the interface created for this inputs are still defined as uint8 a; and also one more struct with the size of the signal.

But i am not sure how can i pass the variable array from another code to the MATLAB code ? As the signal is still defined as a signle variable ?

Answer 1

[Harsh]

Hi @vivek patel,

To create a variable-sized input in Simulink, follow these steps:

1. Configure the Inport Block: In the "Signal Attributes" tab of the Inport block, set "Variable-size signal" to "Yes." Specify the "Port dimensions" to indicate the maximum size for the Inport.
2. Adjust Code Generation Settings: In the "Code Generation" settings, navigate to the "Interface" section and ensure that the "variable-size signals" option is checked.
3. Generate Code: Use the "Embedded Coder" app to generate the code.
4. Examine the Generated Code: In the generated code, open the "model.h" file to see how the input structure is handled. The header file will contain structures like:

  /* External inputs (root inport signals with default storage) */
   typedef struct {
     real_T Inport[1000];                 /* '<Root>/Inport' */
   } ExtU_<modelName>_T;

   /* External input sizes (for root inport signals with variable sizes) */
   typedef struct {
     int32_T Inport;                      /* '<Root>/Inport' */
   } ExtUSize_<modelName>_T;

In the above code -

• The external input structure (ExtU_<modelName>_T) declares an array "Inport[1000]", which serves as a buffer with a maximum capacity of 1000 elements for the input signal. You can specify this maximum size in the Simulink model by setting the "Port dimensions" as described earlier.
• The external input sizes structure (ExtUSize_<modelName>_T) includes an integer field "Inport" that records the current number of valid elements in the input. For instance, if only 200 elements are valid, you would set "<modelName>_USize.Inport = 200".

I hope this explanation clarifies how you can set the input size in the generated code. If you have any further questions, feel free to ask!