Passing parameters for C-Mex S-functions returns only Zero(0)

Hello community,

Currently, I'm troubling around with S-function parameters in Simulink. The S-function are all written in C. I wanted to pass parameters to the S-function, but the passed arguments are always just zero. I don't understand this behavior and nearly rewrote the example given in foogain from the help context.

Here's what I did so far:

• I defined the retrieving function in the header of the S-function C-code:

#define FLAG mxGetPr(ssGetSFcnParam(S,0))[0]

• In the mdlOutputs I just wrote a ssPrintf for debug purposes like this:

ssPrintf( "This is the flag: %d", FLAG ); // the flag parameter is -2 though, the ssPrintf will show zero(0) as output ...

Could you please give me some advice what the problem could be? Thanks in advance.

Answer 1

[Kaustubha Govind]

Could you try %f instead of %d? In this case, FLAG is of type double, but you are using a format specifier that is meant for integers.

Answer 2

[Rob]

Hm, this was indeed the error for my problem. A cast like (int) could avoid that dangerous behavior, too:

ssPrintf( "This is the flag: %d", (int)FLAG );

Thank you Kaustubha.