S-function codegeneraton for rtw: error C2065: 'ssGetData​TypeSize_c​annot_be_u​sed_in_RTW​': undeclared identifier

Hello,

I would like to use this function in an s-function to determine the memory size in bytes of a custom datatype.

// Retrieve the size in bytes of the datatype at the input port

int_T size = ssGetDataTypeSize(S,dtype);

This works fine in simulation, but when generating code for my target, I receive the following error:

error C2065: 'ssGetDataTypeSize_cannot_be_used_in_RTW': undeclared identifier

So probably this is not supported?

This is the only function preventing me to deploy my code on my realtime target.When hardcoding the size, codegeneration and running is succesfull. Therefore I would like to ask if there is an alternative to retrieve the memory size.

Kind regards,

Brecht

[Benjamin Thompson]

Are you using Embedded Coder with a TLC file or Simulink Coder? Can you post any files? In general the SimStruct functions liks ssGetDataTypeSize can only be used in the compiled MEX binary in the Simulink environment, or in Rapid Accelerator.

[Karel Viaene]

We are indeed using Simulink Coder. The final target is a beckhoff PLC running the c++ code.

Would there be an alternative implementation possible for the ssGetDataTypeSize function which is compatible for rtw codegeneration?

I attached the full c++ file which I want to generate code of for a rtw target.

Thank you in advance.

Kind regards,

Brecht

[Benjamin Thompson]

I am not familiar with the PLC products. Are you using Simulink PLC Coder? Are you required to have a TLC file for custom blocks as part of PLC code generation? For Simulink Coder or Embedded Coder generating C/C++ code, the TLC file tells the Target Language Compiler how to generate the source code for your block behavior.

For code generation to C/C++, I would use the C sizeof operator and the TLC function to get the string name of the data type:

int sizeMyType = sizeof(%<LibBlockInputSignalDataTypeName(0,"")>);

The C++ compiler should know the size of all data types.

[Karel Viaene]

Hello Benjamin,

Thank you for your reply. I believe this is exactly what I'm looking for. To clarify, we don't use PLC coder, but generate C++ code with simulink coder.

However I have no experience yet with TLC, so I think I need to learn this first. If I understand correctly, the TLC file will contain an alternative implementation which is interpreted differently at compile time. At compile time te compiler will know all sizes of the input ports and can then 'hardcode' the right value at compiletime.

I will come back to you if I played around with this a bit; already thanks for the help.

kr

brecht

[Karel Viaene]

Hi Benjamin,

I started learning writing tlc using the tutorials. The directive you talked about before works for me. In the generated code it can retrieve the datatype of the input signal on which the sizeof() operator can be applied. Then I was able to generate code with my TLC file corresponding to the S-function c++ code and deploy it on the target.

Still many things to learn about tlc apparently, but it's a start.

thanks for the help!

kr,

Brecht

Answer 1

[Benjamin Thompson]

See this documentation for more information on the Target Language Compiler and some tutorials with instruction on how to use this tool and code TLC:

https://www.mathworks.com/help/rtw/block-authoring-with-tlc.html?s_tid=srchtitle_target%20language%20compiler_1