MATLAB: Using emlc to generate C code – function within a function problem

c-code generationembedded matlabemlc

Hello fellow Matlab users,

Ive been trying to convert a massive code from matlab to c and implement it for real time signal processing on a DSP processor.

So far ive been succesfull and emlc is an amazing function! The problem i have reached now is that I need to compile a code that has the function "butter" inside (gives out butterworth filter coefficients.)

The problem is that the compilation report complains about butter`s input arguments are not constant.

To make things a bit more clear:

C_generating_script.m => Function_1.m => butter.m

Now my question is:

How can I define/declare the inputs of the butter function as constants which is within another function and allow it to compile?

Best Answer

Have you tried specifying constant inputs using emlcoder.egc: http://www.mathworks.com/help/toolbox/eml/ug/bq2wkmb-47.html#brl11_g-1

Related Solutions

MATLAB: How to write C code generation for ‘ not available function for standalone generation’

Do you need to change your filter over the simulation, if not, then the coder.extrinsic approach, as outlined in the error message, would be a good way to go. Essentially you can use MATLAB to compute the coefficients and then perform the filtering.

HTH

MATLAB: Problem Compiling function subset with EMLC

Sorry about that. Since 'high' is a string input, it works better if you use:

emlc Lowpassfilter.m -eg {emlcoder.egc('high')}

I fixed my answer above also.

I corrected your code slightly, and this works

%#eml
function [ output ] = Lowpassfilter ( input )
%assert(isa(input,'int32'));
assert( ~isreal(input)); 
n = 5; Wn = 0.5;
a = zeros(1,n+1);
b = zeros(1,n+1);
[b a] = butter (n, Wn, 'low');
output = filter(b, a, input);

You had two errors:

Variables 'a' and 'b' must be pre-allocated, so I used ZEROS to do this
The function filter cannot take int32 inputs, so I removed the assert for datatype - emlc will probably assume a floating point input now. There is filter in Fixed-Point Toolbox that does allow int32 inputs, but the second parameter should always be 1.

Best Answer

Related Solutions

MATLAB: How to write C code generation for ‘ not available function for standalone generation’

MATLAB: Problem Compiling function subset with EMLC

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