Specify the number of inputs, outputs, states, parameters, and other characteristics of the C MEX S-function
Yes
C, C++
#define MDL_INITIAL_SIZES
void mdlInitializeSizes(SimStruct *S)
S SimStruct representing an S-Function block.
This is the first S-function callback methods that the Simulink® engine calls. This method performs the following tasks:
Specify the number of parameters that this S-function
supports, using ssSetNumSFcnParams.
Use ssSetSFcnParamTunable(S,paramIdx, 0) when
a parameter cannot change during simulation, where paramIdx starts
at 0. When a parameter has been specified as not
tunable, the engine issues an error during simulation (or when in
external mode when using the Simulink
Coder™ product) if an
attempt is made to change the parameter.
Specify the number of states that this function has,
using ssSetNumContStates and ssSetNumDiscStates.
Configure the block's input ports, including:
Specify the number of input ports that this S-function
has, using ssSetNumInputPorts.
Specify the dimensions of the input ports.
See ssSetInputPortDimensionInfo for
more information.
For each input port, specify whether it has direct
feedthrough, using ssSetInputPortDirectFeedThrough.
A port has direct feedthrough if the input is used in either
the mdlOutputs or mdlGetTimeOfNextVarHit function. The
direct feedthrough flag for each input port can be set to either 1=yes or 0=no.
It should be set to 1 if the input, u, is used
in the mdlOutputs or mdlGetTimeOfNextVarHit routine.
Setting the direct feedthrough flag to 0 tells the Simulink engine
that u is not used in either of these S-function
routines. Violating this leads to unpredictable results.
Configure the block's output ports, including:
Specify the number of output ports that the block
has, using ssSetNumOutputPorts.
Specify the dimensions of the output ports.
See mdlSetOutputPortDimensionInfo
for more information.
If your S-function outputs are discrete (for example, the outputs
only take specific values such as 0, 1, and 2), specify SS_OPTION_DISCRETE_VALUED_OUTPUT.
Set the number of sample times (i.e., sample rates) at which the block operates.
There are two ways of specifying sample times:
Port-based sample times
Block-based sample times
See Specify S-Function Sample Times for a complete discussion of sample time issues.
For multirate S-functions, the suggested approach to setting
sample times is via the port-based sample times method. When you create
a multirate S-function, you must take care to verify that, when slower
tasks are preempted, your S-function correctly manages data so as
to avoid race conditions. When port-based sample times are specified,
the block cannot inherit a sample time of Inf at
any port.
Set the size of the block's work vectors, using ssSetNumRWork, ssSetNumIWork, ssSetNumPWork, ssSetNumModes, ssSetNumNonsampledZCs.
Set the simulation options that this block implements,
using ssSetOptions.
All options have the form SS_OPTION_<name>. See Configure C/C++ S-Function Features for information on each
option. Use a bitwise OR operator to set multiple options, as
in
ssSetOptions(S, (SS_OPTION_name1 | SS_OPTION_name2))
Note
If you have Simulink
Coder, when generating code for a noninlined
S-function that contains this method, make sure the method is not
wrapped in a #if defined(MATLAB_MEX_FILE) statement.
For example:
#if defined(MATLAB_MEX_FILE)
static void mdlInitializeSizes(SimStruct *S)
{
/* Add mdlInitializeSizes code here *
}
#endif The define statement makes the mdlInitializeSizes method
available only to a MATLAB® MEX file. If the S-function is not
inlined, the Simulink
Coder product cannot use this method,
resulting in link or run-time errors.
You can set the parameters NumContStates, NumDiscStates, NumInputs, NumOutputs, NumRWork, NumIWork, NumPWork, NumModes,
and NumNonsampledZCs to a fixed nonnegative integer
or tell the Simulink engine to size them dynamically:
DYNAMICALLY_SIZED -- Sets lengths
of states, work vectors, and so on to values inherited from the driving
block. It sets widths to the actual input widths, according to the
scalar expansion rules unless you use mdlSetWorkWidths to
set the widths.
0 or positive number -- Sets lengths
(or widths) to the specified values. The default is 0.
The Level-2 MATLAB S-function setup method
performs nearly the same tasks as the C MEX S-function mdlInitializeSizes method.
static void mdlInitializeSizes(SimStruct *S)
{
int_T nInputPorts = 1; /* number of input ports */
int_T nOutputPorts = 1; /* number of output ports */
int_T needsInput = 1; /* direct feedthrough */
int_T inputPortIdx = 0;
int_T outputPortIdx = 0;
ssSetNumSFcnParams(S, 0); /* Number of expected parameters */
if (ssGetNumSFcnParams(S) != ssGetSFcnParamsCount(S)) {
/*
* If the number of expected input parameters is not
* equal to the number of parameters entered in the
* dialog box, return. The Simulink engine generates an
* error indicating that there is aparameter mismatch.
*/
return;
}else {
mdlCheckParameters(S);
if (ssGetErrorStatus(S) != NULL)
return;
}
ssSetNumContStates( S, 0);
ssSetNumDiscStates( S, 0);
/*
* Configure the input ports. First set the number of input
* ports.
*/
if (!ssSetNumInputPorts(S, nInputPorts)) return;
/*
* Set input port dimensions for each input port index
* starting at 0.
*/
if(!ssSetInputPortDimensionInfo(S, inputPortIdx,
DYNAMIC_DIMENSION)) return;
/*
* Set direct feedthrough flag (1=yes, 0=no).
*/
ssSetInputPortDirectFeedThrough(S, inputPortIdx, needsInput);
/*
* Configure the output ports. First set the number of
* output ports.
*/
if (!ssSetNumOutputPorts(S, nOutputPorts)) return;
/*
* Set output port dimensions for each output port index
* starting at 0.
*/
if(!ssSetOutputPortDimensionInfo(S,outputPortIdx,
DYNAMIC_DIMENSION)) return;
/*
* Set the number of sample times. */
ssSetNumSampleTimes(S, 1);
/*
* Set size of the work vectors.
*/
ssSetNumRWork(S, 0); /* real vector */
ssSetNumIWork(S, 0); /* integer vector */
ssSetNumPWork(S, 0); /* pointer vector */
ssSetNumModes(S, 0); /* mode vector */
ssSetNumNonsampledZCs(S, 0); /* zero crossings */
ssSetOptions(S, 0);
} /* end mdlInitializeSizes */