How to determine simulink input in real time using arrow keys

When executing a Simulink model, I want the output to be pi/8 while the up arrow key is pressed, -pi/8 while the down arrow key is pressed, and zero otherwise (when both arrow keys are released).

I'd like to detect key inputs in real-time during simulation, and update the output at each simulation step.

I use a MATLAB Function block in Simulink. The program for the MATLAB Function block is as follows:

function out = fnc()
% get handle to use GetKeyInput function
h = @GetKeyInput;
out = h();
end

The program for the external function, GetKeyInput.m, is as follows:

function output = GetKeyInput()
persistent outputValue; 

if isempty(outputValue)
    outputValue = 0; % initial
end

fig = gcf;

% get ket input
keyInput = get(fig, 'CurrentCharacter');

switch keyInput
    case 30 % uparrow ASCIIcode:30
        outputValue = pi/8;
    case 31 % downarrow ASCIIcode:31
        outputValue = -pi/8;
    case 28
        outputValue = 0;
end

% output
output = outputValue;
end

When running this Simulink model, I encounter the error as follow:

Cannot pass a mxArray to 'eml_switch_helper'.

Function 'GetKeyInput.m' (#29.195.203), line 13, column 8:
"keyInput"
Launch diagnostic report.

How can I get the simulation to work?

Answer 1

[covao]

This is caused by using a MATLAB function block that is not supported by code generation.

Please refer to the following document for details.

https://mathworks.com/help/simulink/ug/integration-considerations-for-matlab-function-blocks.html

A simple solution is to use Interpreted MATLAB Function.

Set GetKeyInput() to the block parameter.