Reading a wire value from Simulink into the Command Window or GUIDE

I want to read the values that passes through a wire in my Simulink model.

This value should be displayed in a text field on a MATLAB GUI (it's the water level in a tank that is acquired every 100 ms).

I found out about get_param instruction, but until now I only managed to get the values from constants and transfer functions; example: get_param('main/Constant','Value') ; get_param('main/Transfer Function','Denominator').

How do I address a wire and its property list (value)?

The data is generated by an OPC Read block, passing through a subsystem using an Out port.

Answer 1

[Kaustubha Govind]

Please see Access Block Data During Simulation

Answer 2

[River Rock]

Thanks for your answer; I was able to get the data from the filter's output

data=get_param('main/level/level_filter','RuntimeObject'); lvl = data.OutputPort(1).Data;

It works ok by request

How can I display this data cyclically in a Static Text field on a GUI ? Is there some callback that runs periodically ( and the sample time can be specified) ?

[Kaustubha Govind]

Yes, there is an event-listener mechanism that will invoke your callback every time there is a new output. Please see the "Listening for Method Execution Events" section in the page I linked above.

[River Rock]

I added the following code in the gui m file:

function pushbutton1_Callback(hObject, eventdata, handles)

set_param('main','SimulationCommand','start');

iev = add_exec_event_listener('main/nivel/MATLAB Function','PostOutputs',@fetch_data);

function fetch_data(block, eventData)

set(handles.text3,'String','does_it_work');

Doesn't seem to work. What am I doing wrong?

UPDATE: It works if I type the add_exec_event_listener instruction in the Command Window, provided that fetch_data is a stand-alone function. In the GUI it still doesn't work.

[Kaustubha Govind]

Is fetch_data part of the GUI function? I think that it should indeed be a standalone function. You can cache the GUI "handles" object onto the block's UserData. Haven't tested this myself, but how about:

In GUI file:

function pushbutton1_Callback(hObject, eventdata, handles)

set_param('main/nivel/MATLAB Function', 'UserData', handles);
set_param('main','SimulationCommand','start');
iev = add_exec_event_listener('main/nivel/MATLAB Function','PostOutputs',@fetch_data);

In a standalone function:

function fetch_data(block, eventData)
handles = get_param(block.BlockHandle,'UserData');
set(handles.text3,'String','does_it_work');

[River Rock]

I found a workaround yesterday. But your solution looks more elegant, I had to use global variables.

Thanks for your great support, the problem is solved.