Simulink get rid of error that block doesnt support variable size input

Dear all I am using Simulink and its great except this error who i cannot get rid of

Simulink cannot propagate the variable-size mode from the output port 1 of 'Framing/FrameGenerator/AddEscapeCharacter' to the input port 1 of 'Framing/FrameGenerator/Buffer'. This input port expects a fixed-size mode. The variable-size mode originates from 'Framing/FrameGenerator/AddEscapeCharacter/Switch'. Examine the configurations of 'Framing/FrameGenerator/Buffer' for one of the following scenarios: 1) the block does not support variable-size signals; 2) the block supports variable-size signals but needs to be configured for them.

I want to generate frames who are buffered in a buffer, and the buffer block cannot accept variable size input ??! Is there any quick workaround this except not using buffer block ? If this is not possible i think Simulink is quite weak to deal with variable size signals

Answer 1

[Shubham]

Hi Timo,

The error you're encountering in Simulink is related to the handling of variable-size signals. Simulink does support variable-size signals, but not all blocks are compatible with them, and some require specific configurations to handle such signals.

Understanding the Error

The error message indicates that the Buffer block expects a fixed-size input, but it is receiving a variable-size signal from the AddEscapeCharacter block. This is a common issue when trying to handle variable-size data in a system that includes blocks that do not natively support it.

Possible Solutions and Workarounds

1. Check if the Buffer block can be configured to handle variable-size signals. Some blocks have parameters that allow them to work with variable-size data. Look for options related to signal dimensions in the block parameters.
2. If the Buffer block cannot be configured to accept variable-size signals, consider using an alternative block that supports variable-size data. For example, you might use a MATLAB Function block or a Stateflow chart to implement custom buffering logic.
3. If possible, transform the variable-size signal into a fixed-size signal before it reaches the Buffer block. This might involve padding the signal to a fixed size or using a custom logic to handle different frame sizes.
4. Implement a custom buffering mechanism using a MATLAB Function block. This allows you to write MATLAB code that can dynamically handle variable-size signals.

function y = customBuffer(u)
%#codegen
% Implement your custom buffering logic here
% Example: simple pass-through
y = u;
end

5. Variable-Size Support: Use blocks that explicitly support variable-size signals. Simulink has some blocks designed to handle variable-size data, and using these can simplify the process.