Real-Time Processing with Matlab

I have to build a MATLAB GUI that controls an instrument (Network Analyzer), gets it results in real-time and has to process some results without effecting the real-time regime of data collection. The processing includes building current preview image of the results and some manipulations like interpolation and fft.

The question is, how can I be sure that the processing will not effect the real-time budget of the instrument? Is there is a way to command Matlab not to wait for the results of processing if the instrument passes another piece of data in order to be able to collect all the data without omitting a part of it?

For example, if the Cycle of the arrival of data from the Network (NA) is T, the time of collection from the NA is Tc, and the time of Processing is Tp. How can I ensure that Matlab will be ready to collect the data every T time, no matter what is the Tp? Even if Tp<T-Tc, sometimes Matlab has its delays of processing, as it is not real-time program. What can be done to prevent the effect of such delays?

For addition, if Tp>T-Tc, how the processing can be commanded to be executed at the "background" without effecting the cycle of the collection?

Answer 1

[Ameer Hamza]

See timer(). You can set the timerFcn to run every T seconds. The timer will run in the background and every T seconds, the timer will run and perform the function specified by timerFcn property regardless of what is executing. You can read the data and store it in a variable in the callback function. For example

t = timer('ExecutionMode', 'fixedRate', 'Period', 2, 'TimerFcn', @receiveData)
start(t)

You can define a function receiveData and place it in MATLAB path. timer will execute it every 2 second.

[Gavriel Aminov]

Ameer, thank you for your answers.

[Ameer Hamza]

You are welcome.

Answer 2

[Gavriel Aminov]

Thanks for the tip! What about the next Note at the documentation?

The timer object is subject to the limitations of your hardware, operating system, and software. Avoid using timer objects for real-time applications.

[Ameer Hamza]

Since you are not working on a real-time OS, such an issue can always happen. It depends on the complexity of the algorithm you are applying on the data. If the complexity is small, then probably it will not create an issue. Alternatively, you can refer to this FEX submission to get further ideas.

[Ameer Hamza]

You can also refer to this answer. A hard real-time constraint cannot be guaranteed in MATLAB.

[Guillaume]

I feel it's worth repeating: A hard real-time constraint cannot be guaranteed. Note that this is not matlab that cannot guarantee this, but your OS.

[Gavriel Aminov]

Guillaume, thank you.