Setparam on a nested block

Hello,

I'm trying to use setparam command to modify blocks in a Simulink Real-Time model through a GUI built in App Designer. I was able to change a constant block value in the "first layer" of the Simulink model by using a command like:

setparam(tg,'Constant','Value',1)

At the same time, when trying to set similar constant blocks within subsystem blocks (so lower layers of the Simulink model), I'm getting "invalid parameter" error. The command I'm using is pretty much similar but providing the path to the Constant block. Something like this:

setparam(tg,'Layer1/Layer2/Constant','Value',1)

To be honest, I was able to change parameters at the 2nd level, but not deeper than that.

Is there some sort of limitation in using this setparam command? I couldn't find any reference online but maybe you can help here.

Like, is the problem if the layer name contains spaces (e.g. "Layer 1" instead of "Layer1")? Or maybe it's really limited to one level of nesting?

I'm on Matlab 2020a.

Thanks for any help in advance! :)

[Tommaso Proietti]

Ok I found the solution. The block I was trying to modify was not containing a value but a variable name and this type of constant block is considered a global parameter in Simulink Real-Time. To access a global parameter, the code is the following:

setparam(tg,'Variable Name',value)

Answer 1

[Fangjun Jiang]

There is no limitation regarding how deep can you go to reference the block. The only thing that might prevent you from doing this directly is that the block is inside a library link.

But first, please verify that you've done it correctly in the basic syntax

setparam(tg,'Constant','Value',1) is no good.

It should be something like this

set_param('ModelName/Layer1/ConstantBlockName','Value','1')

[Tommaso Proietti]

Hi Fangjun,

Thanks for the answer. What do you mean by inside a library link? I think all the blocks I tried to access are inside subsystem I built.

For the basic syntax, I was doing the same mistake as you and I spent like 2 hours before understanding it. There are actually two very similar but very different set param commands, one for non-real-time applications (https://www.mathworks.com/help/simulink/slref/set_param.html), one for real-time applications (https://www.mathworks.com/help/xpc/api/setparam.html). The difference is the underscore sign and the number of inputs. So I need the one for real-time applications. ;)

[Fangjun Jiang]

Ok, this is for Simulink Real-Time target. I don't have such a target so I can't try.

Looking at the document, it says "Hierarchical name of the originating block" but none of the examples contains hierarchical names. I believe it is true since you said it worked for blocks in your 2nd layer subsystem. I don't think there is a limitation on the number of layers. The only thing I can think of is that the block parameter has to be specified as "tunable".

It is unlikely that every block and every parameter is accessible in Simulink Real-Time target. Some could be optimized out during code generation. Make sure the block parameters you try to change are specified as "tunable".

If you still have difficulties, contact the Mathworks Tech Support.

[Tommaso Proietti]

Cool, thanks for your hints!