How can I generate an output pulse in Simulink every time a function-call trigger occurs?

I have an existing Simulink model from a customer that uses function-call semantics as event triggers on Stateflow charts, amongst other things.

For our current purposes, I need to be able to generate a simple output pulse when a function-call trigger occurs, such that:

-> At the function call trigger, we set the output to value 1

-> After a fixed period of time (e.g. 1ms), the output value is set to 0.

And this then repeats whenever the function call trigger next occurs.

I tried setting up a stateflow chart as follows:

And although this does generate a pulse, the transition from High to Low state only occurs when the E event occurs, rather than 1ms after when the initial E event occurred. That is, it is obvious that the chart is going to sleep in between the E function-call events.

The E events are around 200ms apart, and each pulse of 'y' is also the same width - when I want it to only be 1ms wide when y=1.

Is there a way to change the chart settings so that it stays awake until the transition from High back to Low has occurred?

Or could I acheive the same behaviour using a Function-call subsytem instead of a Stateflow chart? Either is fine for me.

(The overall model uses a Variable solver, as the block generating the function-call pulses requires it.)

Answer 1

[Danny S]

So after some experimentation, here's a solution that seems to be working for me.

The chart:

This lives inside the following subsystem:

The FunctionCall input comes from the customer block that generates occasional function calls. The 1ms function call has a sample time of 0.001. These are muxed to the input events of the chart as E and M1 respectively.

Within the chart, the function call E will transition from Low state to High state and set y=1; Then, after 2 instances of the M1 event, we transition back to low and set y=0.

It does seem odd that I need to wait for 2 instances of M1, rather than just having the transition as M1 - but given that E and M1 will both occur at the same time (generally, E is at a microsecond boundary), without the after(2, M1) transition, I could see the state transitions happening by using debug breakpoints and stepping, but they were both occurring at the same time step thus the pulses were 0 time in width.

With the above chart, I can see (via a Scope of the value of y) that I'm getting y pulses with width 1ms, and they start at the same time as E.

If someone has any better solutions, please feel free to submit them too!