MATLAB: Do I receive an error message when generating code for an EML block which has a structure field name as OVERFLOW in in Simulink 7.2(R2008b)

emlmacrooverflowsimulink coderunderflow

I tried to generate code for a simple EML block using Simulink 7.2(2008b). The EML block contains the following line:

Cmd_Status.OVERFLOW = 16;
y=u;

I expected the model including the EML block to compile, run and the output to match the constant input of 1. However, I receive the following error message:

 Error EML_bug_sfun.c: .\c2_EML_bug.h: 14  syntax error; found `3' expecting `;' 
 Error EML_bug_sfun.c: .\c2_EML_bug.h: 14  skipping `3'

Best Answer

This is an expected behaviour because there is a clash between the field name and an existing MACRO. The keyword OVERFLOW is already defined in math.h which is included while building the EML block.

As a workaround, use a different name(OVERFLOW1) or lowercase name (overflow) for the structure field.

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MATLAB: Do I get the error “The PERSISTENT declaration must precede any use of the variable XXX” even though PERSISTENT is the first line of the function

This bug has been fixed in Release 2007b (R2007b). For previous product releases, read below for any possible workarounds:

The error message could perhaps be more specific for this case, but is not incorrect. If you consider the first line of your function to be the function declaration statement

function out = myfun(in)

then variable ‘out’ is indeed being used before being declared in the next line as persistent.

The general rule to keep in mind here is that persistent variables cannot be used for input or output arguments to a function. This is not stated in the documentation, but will be added.

MATLAB: Do I receive an error when I pass in 2 vectors of different lengths to the ‘2-D Lookup Table’ block in Simulink 7.2(R2008b)

The ability to accept two vectors of different lengths is not supported by the '2-D Lookup Table' block in Simulink 7.2(R2008b).

The block does not loop through each possible input combination. The case is different in case of one scalar and one vector input when the scalar expansion rule applies - the '2D Lookup Table' block supports scalar expansion.

As a possible workaround, the matrix of values can be prepared in advance. This can be done using two methods:

a) Embedded MATLAB block

b) FOR loop iterating subsystem

The Embedded MATLAB block can be easily implemented using the MESHGRID function. However, the FOR loop iterating subsystem is more complicated, because all the values have to be put back together. We can use the fact that the '2D Lookup Table' block can handle scalar expansion to avoid using nested for loop.

Although either of the above two methods can be used, please note that the decision of the better approach of the above two depends on the size of his matrix and the operation involved.If Embedded MATLAB block with the MESHGRID function is used, it will create two buffers of the same signal and for large matrices this may cause a memory issue.

If the FOR loop iterating method is used, the '2D Lookup Table' block has to be called multiple times and it might increase the length of execution time.

In addition, code is generated for the model, the generated code will be different depending on the approach that is adopted.

Best Answer

Related Solutions

MATLAB: Do I get the error “The PERSISTENT declaration must precede any use of the variable XXX” even though PERSISTENT is the first line of the function

MATLAB: Do I receive an error when I pass in 2 vectors of different lengths to the ‘2-D Lookup Table’ block in Simulink 7.2(R2008b)

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