How can I define some initialization commands in a s-function block in Simulink depending on a declarated variable from the Matlab command window ?

Hi, I have a subsystem masked in Simulink which contains initialization commands that are used depending on a declared variable from the Matlab command window (called Bcaso) - I converted my subsystem into a s-function block, which does not depend on Bcaso. I need that my s-function block can be executed depending on Bcaso. Thanks!

Answer 1

[Seth Popinchalk]

S-functions can include parameter inputs. There are examples of this for Level 2 MATLAB S-function, (msfcndemo_limintm) and C-MEX S-functions, (see sfundemos).

In a Level 2 MATLAB S-function, during "setup" set the number of dialog parameters:

 block.NumDialogPrms = 3;

Anywhere you need to reference a parameter (for example) inside "InitConditions" you can access it through the block object:

 block.ContStates.Data = block.DialogPrm(3).Data;

The parameters are passed into the block through the S-function block parameters, separated by commas.

For C-MEX S-functions, use ssSetNumSfcnParams in mdlInitializeSizes to set the number of parameters and ssGetSfcnParam to get a pointer to an mxArray anywhere you need to use it. C-MEX S-functions also need to do some parameter checking, so it can get a lot more complicated. See the SFCNDEMOS for examples.