MATLAB: Is there an example that explains how to use a PWork vector in an S-function in Simulink 7.3 (R2009a)

pworksimulink

I need to use a PWork vector in my S-Function. However, I am not able to find any useful information or a simple example in the documentation regarding the same.

Best Answer

The ability to use a PWork vector in an S-function is available in Simulink 7.3 (R2009a). Download the attached files for a complete example that illustrates the setup and very simple use of a PWork vector in an S-Function. It uses a PWork vector to store a counter.

Refer to the steps below, which is a snippet of the attached code, in order to use a PWork vector in an S-function.

1) Set the number of pointers in the PWork vector.

ssSetNumPWork

2) Allocate the memory.

p_work_vector_target_data_handle = (double *) malloc( sizeof(double) );

3) Initialize the counter to 0.

(*p_work_vector_target_data_handle) = 0.0;

4) Retrieve the PWork vector value.

p_work_vector_element = ssGetPWorkValue(S, 0);

5) Increment and set the PWork vector value.

(*p_work_vector_element) = (*p_work_vector_element) + 1  
(*output_port_data_pointer) = (*p_work_vector_element);

6) Set the PWork vector to NULL.

void ** p_work_vector = NULL;

7) Clear the memory.

free(p_work_vector_element);

Related Solutions

MATLAB: How to allocate and free memory for a PWork vector in a C-MEX S-function

First, the S-Function needs to specify how many PWork vectors it needs (using ssSetNumPWork) either in mdlInitializeSizes or in mdlSetWorkWidths. Simulink calls the above functions in the S-Function at the beginning of the model initialization stage (internally we refer to this part of the initialization stage as the compile phase). Towards the end of model initialization stage (internally we refer to this part of the initialization stage as the link phase), Simulink allocates the specified number of PWorks. Upon completing the model initialization stage, Simulink calls the S-Function's mdlStart. In the mdlStart function, the S-Function can allocate memory and store a pointer to it in the PWork array. The following code snippet illustrates specifying, allocating, using, and freeing memory using PWorks.

mdlInitializeSizes(SimStruct* S) 
{ 
/* snip */
ssSetNumPWork(S, 1);
/* snip */ 
}
mdlStart(SimStruct* S) 
{ 
/* snip */
void* ptr = malloc(1024 /* number of bytes */); 
if (ptr == NULL) { 
/* report memory allocation error */ 
ssSetErrorStatus(S, "Memory allocation error"); 
return; 
} 
ssSetPWorkValue(S, 0, ptr);
/* snip */ 
}
mdlOutputs(SimStruct* S, int_T tid) 
{ 
void* ptr = ssGetPWorkValue(S, 0);
/* snip */ 
}
mdlTerminate(SimStruct* S) 
{ 
/* snip */
/* free the memory allocated in mdlStart */ 
if (ssGetPWork(S) != NULL) { 
void* ptr = ssGetPWorkVale(S,0); 
if (ptr != NULL) free(ptr); 
}
/* snip */ 
}

For a more complete example on using PWork vectors please look at the following example in the documentation.

http://www.mathworks.com/help/releases/R2009b/toolbox/simulink/sfg/bre1pj2.html#bre1ps0

MATLAB: Is there a way to directly load the data from a text file into a S-function in Simulink 7.0 (R2007b)

Below are the steps that you can use to read data directly from a text file into Simulink S-function as a source:

1. Specify the sizes and the sample time for the S-function.

2. Open the file by using the FOPEN function in the mdlStart or the mdlInitializeConditions function.

3. Store the pointer in a PWork vector for later use.

4. In the mdlOutputs function, obtain the file pointer from work storage and use the FSCANF to read the next element.

5. Then close the file using the FCLOSE in mdlTerminate.

See the attached simple example model 'test_textSource.mdl' which reads the data from a text file 'input.txt' into an S-function.

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Related Solutions

MATLAB: How to allocate and free memory for a PWork vector in a C-MEX S-function

MATLAB: Is there a way to directly load the data from a text file into a S-function in Simulink 7.0 (R2007b)

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