How to extract MIDI data from mxarray in simulink ?

Hello,

For a project, I need to use a MIDI controller that sends MIDI files for the keys pressed (so the MIDI message is a 'NoteOn' or 'NoteOff'). To do so, I chose to use a matlab function block and inside it, i wrote a code using midireceive('MidiInput') function (In order to do that, i used coder.extrinsic('midireceive'). Unfortunately, the results from that is that I got the data from my MIDI controller in a mxarray and I don't know how to extract the data correctly (I juste have to know when a key is pressed and which one it is).

Answer 1

[Swaraj]

To extract the MIDI data correctly from the “mxarray” received by the “midireceive()” function in Simulink, you can use the following steps:

1. Add a MATLAB Function block to your Simulink model.
2. Inside the MATLAB Function block, use the “coder.extrinsic()” function to declare the “midireceive()” function as an extrinsic function.
3. To receive MIDI data from the MIDI controller, use the “midireceive()” function.
4. Use the “cell()” function to transform the “mxarray” into a cell array.
5. Loop over the elements of the cell array and extract the MIDI message using the “midimsg()” function.
6. To detect whether a MIDI message is a "NoteOn" or "NoteOff" message, look at the message's status byte.
7. Similarly you can extract other details like “channel”, “note”,” velocity” etc.

For more details you can go through the following Documentations.

Documentation for “midireceive”.

Receive MIDI message from MIDI device - MATLAB midireceive (mathworks.com)

Documentation for “mxArrays”.

Work with mxArrays - MATLAB & Simulink (mathworks.com)

Documentation for Cell Arrays.

Cell Arrays - MATLAB & Simulink (mathworks.com)