1. S-Functions in Simulink
Using Matlab and S-Function Builder

2. S-Functions Stands for “System Functions”
Custom-built Simulink blocks using C, C++, Fortran, or Matlab.
Makes use of a special S-function API
Involve three main concepts: Inputs, Outputs, and Action

3. Why do we need them? To simplify complex Simulink models
To handle external hardware, programs, or files
To cut calculation time
Event-specific reactions in code (excluding matlab)

4. Simulink – Gain Block
Gain: Take input, multiply by value to produce output.

5. Matlab Example – Gain Block
Replace gain block with custom s-function
One input
Multiply by 2
One output

6. Matlab Example – Gain Block
Check out the code now: s_doubler.m

7. Function Builder Example – Gain Block

8. Simulink – Product Block
Product: Takes numerous inputs and multiplies them together

9. Matlab Example – Product Block
Simply replace product block with your Matlab S-Function Block
2 Inputs
Amount defined by internal code
Operates exactly the same

10. Matlab Example – Product Block
Check out the code now: s_multiplier.m

11. Function Builder Example – Product Block

12. Matlab Example – Throttle Limiter
Input: Wave from -100 to 100, with noise
Desired output:
Scale between -1 and 1, even with noise

13. Matlab Example – Throttle Limiter

14. Simulink Example – Throttle Limiter
Built after Matlab S-Function
Works entirely the same

15. Function Builder Example – Throttle Limiter

16. Creating an S-Function - Matlab
Load up the template.m file
Let’s walk through the throttle limiter

17. Creating an S-Function – Function Builder
Load up the fb_limiter.mdl
Let’s walk through the steps