MATLAB: Set_param() equivalent inside Simulink

guisimulink

I may be missing the obvious here, but here's my question:

I use a MIDI controller to select one of three outputs of my Simulink model via buttons on that MIDI controller.

I have that Simulink model synced with a GUI (no easy feat by itself), but only one-way sync right now: in the GUI I display which output is selected using the event listener functions.

So Simulink model –> GUI works okay-ish.

Now I want the user to be able to also select via the GUI which output is active.

I could use a constant block supplying an input to my output selector and change that value using set_param() from the GUI. But how would I change that constant value from inside Simulink? set_param() does not work inside embedded Matlab, and I need to compile the model for performance reasons (i.e. I can't use coder.extrinsic).

Best Answer

In general, it is discouraged to change a block's parameter from another block (see the blog post How Do I Change a Block Parameter Based on the Output of Another Block?). Why not just get rid of the Constant block and create an output to the Embedded MATLAB block that controls the output Selector directly?

Related Solutions

MATLAB: How to update a GUI with values from the Simulink model as it is running

There is no direct way to access the runtime parameters of a Simulink model from a MATLAB GUI. To work around this issue, you need to create a function that will update the GUI with the desired model data at each time step. An outline of this procedure is as follows.

1. Create a GUI with a control that you would like to update with information from the model. In this example, we would like to see the output of the model's Gain block in the GUIs edit text window.

2. Create a model callback function that will register an event listener for the block in question. This function will be called every time the block is updated. We will use it to access the value of the Gain blocks output and pass them to the GUI. In this case we will use the models 'StartFcn' callback.

%The GUI handles are by default hidden, turn them on
set(0,'ShowHiddenHandles','on');
%Set up the arguments that will go into the gain block event callback listener
blk = 'mytestmdl/Gain';
event = 'PostOutputs';
listener = @updategui;
%Create the listener
h = add_exec_event_listener(blk, event, listener);

3. Create a MATLAB file function that will get the Gain block's runtime output parameter and pass it to the GUI.

function varargout = updategui(varargin)
%create a run time object that can return the value of the gain block's
%output and then put the value in a string.  
rto = get_param('mytestmdl/Gain','RuntimeObject');
str = num2str(rto.OutputPort(1).Data);
%get a handle to the GUI's 'current state' window
statestxt = findobj('Tag','curState');
%update the gui
set(statestxt,'string',str);

MATLAB: Set_param() in Repeating Sequence / Simulink doesn’t work

Variables in the workspace are initialized once during model update before the simulation runs. Therefore, a change in value of the variable in the workspace will not reflect a change in value of the block parameter during simulation.

You can however change the value of the parameter directly by assigning the value of the workspace variable to the block with the following command:

set_param(gcb , 'rep_seq_y' , ['[' num2str(a) ']'])

Where 'a' is some row vector.

Alternatively, after you change the workspace variable, you can force a model update to ensure any changes in workspace variables are reflected in the model during simulation:

set_param(bdroot , 'SimulationCommand', 'update')

Best Answer

Related Solutions

MATLAB: How to update a GUI with values from the Simulink model as it is running

MATLAB: Set_param() in Repeating Sequence / Simulink doesn’t work

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