How to create a sawtooth signal inside an S-function ?

Hi,

I'm working with C-MEX S-function (C code). I was wondering if it is possible to create a sawtooth signal inside a C-coded S-function and see the signal with the Simulink scope. If it is possible, how to do it ?

Thanks for your help

Answer 1

[TAB]

A simple demonstration:

1. Drag a S-function builder block in the model.
2. Configure S-function having only 1 output (y[0]). No input, No discrete state, No continuous state.
3. In the output function write code given below
4. Build the S-function and run the model.

y0[0] = y0[0]+1;
if(y0[0]>UPPER_LIMIT)
{
    y0[0] = 0;
}

[Alice]

Thank you for your help, it works

Answer 2

[Alice]

Is it possible to do the same signal inside an S-function without having an output port ? The signal would be compared to the input signal.

[TAB]

How will you get the sawtooth signal output without output port ?

[Alice]

It won't exactly be an output signal. Actually, the sawtooth signal would be created inside the S-function to stay in the block and each point would be compared to the points of the input signal. The output would be the display of on/off leds ont the board I have.

[TAB]

In your S-function builder block

• 1 output (y[0]) for LED,
• 1 input (u[0]) for comparing
• 1 discrete state (xD[0]) for storing Ramp value
• No continuous state.

In your S-function builder Discrete update field

xD[0] = xD[0] + 1;
if(xD[0]>=UPPER_LIMIT)
{
    xD[0] = 0;
}

In your S-function builder Outputs field

if(xD[0]>=u0[0])
{
    y0[0] = 1; /*LED ON*/
}
else
{
    y0[0] = 0; /*LED OFF*/
}

Please go through the s-function document.