User`s guide

Writing Basic C MEX S-Functions
3-9
• mdlOutput:
- The numerical calculation.
mdlOutputs tells S imulink to multiply the
input signal by 2.0 and place the result in the output sig nal.
- To access the input signal, use:
InputRealPtrsType uPtrs = ssGetInputPortRealSignalPtrs(S,0);
where uPtrs is a vector of pointers and must be accessed using:
*uPtrs[i]
For more details, see “Data View of S-Functions” on page 3–19.
- To a ccess the output signal, use
real_T *y = ssGetOutputPortRealSignal(S,0);
This returns a contiguous a rray for the block’s outputs.
- The S -function loops o ver the width of the signal passing through the
block. To access the width, you can check the input or output port width.
Here the output port width was evaluated.
•
mdlTerminate:
- This is a mandatoryS-function routine. However, the
timestwo S-function
doesn’t need to perform any termination actions, so this routine is empty.
• Atthe end ofthe S-function,specifycode thatattaches this exampleto either
Simulink or the Real-Time Workshop:
#ifdef MATLAB_MEX_FILE
#include "simulink.c"
#else
#include "cg_sfun.h"
#endif