How to convert to C-code from MATLAB code by using MATLAB CODER for case of Low-pass filter

Situation:

1) I made a low-pass filter by using Filter-Designer.

2) I exported a function with MATLAB code by using Filter-Designer.

3) I added a script for calling the function as MATLAB code .

4) I convert to a C code from the MATLAB code. Then I cannot convert to a C code.

Created MATLAB code:

Low-pass Filter:

function Hd = untitled
%UNTITLED 離散時間フィルター オブジェクトを返します。

% MATLAB Code
% Generated by MATLAB(R) 9.9 and Signal Processing Toolbox 8.5.
% Generated on: 02-Feb-2022 10:51:19

% FIR Window Lowpass filter designed using the FIR1 function.

% All frequency values are in Hz.
Fs = 1000;  % Sampling Frequency

N    = 20;       % Order
Fc   = 48;       % Cutoff Frequency
flag = 'scale';  % Sampling Flag
Beta = 0.5;      % Window Parameter

% Create the window vector for the design algorithm.
win = kaiser(N+1, Beta);

% Calculate the coefficients using the FIR1 function.
b  = fir1(N, Fc/(Fs/2), 'low', win, flag);
Hd = dfilt.dffir(b);

% [EOF]

Script:

Fs = 2882;
t = linspace(0,1,Fs);
y2 = filter(Hd,x);
plot(t,x,t,y2);
t = linspace(1,2882,Fs);
plot(t,x,t,y2);

How can I convert the above MATLAB code using MATLAB Coder?

Could you please tell me the method and procedure?

[Walter Roberson]

I seem to recall that the general technique is to design the filter first, and save it to a .mat file, and then create a function (not a script) that load()'s the filter from the file and uses it.

If I recall, the load() will effectively be done at compile time, and the filter effectively becoming hard-coded.

[Mitsuhiro OTSUKI]

Thank you for your prompt response.

Thank you for your advice too.

First, I will try.

[Raghu Boggavarapu]

Do you want to generate the code for the function that generates filter coefficients ?

[Walter Roberson]

As their script does not show invoking the design function, I suspect they want to generate code for using the designed filter. (If I recall correctly, the design functions are not supported for code generation.)

[Mitsuhiro OTSUKI]

@Walter Roberson san

Thank you for your advice. It was carried out as you said. However, I get a message that discrete and structured variables stored in the workspace in .mat are not supported.

I will contact the support center.

[Mitsuhiro OTSUKI]

@Raghu Boggavarapu san

Thank you for your consideration. Yes, I do. I want to generate the code for the function that generates filter coefficients.

Then I want use filter coefficients for multiply the raw data by the filter coefficients.

[Walter Roberson]

As far as I can see, code cannot be generated for the filter design functions that you are using. (I did not check whether you can generate for simpler functions such as butterord)

[Mitsuhiro OTSUKI]

Thank you @Walter Roberson for your kindly information.

I understood regarding you said.

I think I want to select the other function.

Answer 1

[Benjamin Thompson]

Here is the online documentation page for functinos in the Signal Processing Toolbox that can be generated to C/C++:

https://www.mathworks.com/help/signal/referencelist.html?type=function&capability=codegen

Your code can only use these functions if you want to generate C/C++ code using MATLAB Coder.

[Mitsuhiro OTSUKI]

Thank you @Benjamin Thompson for your answer.

I understood that "dfilt.dffir" is out of usage for generating.

I'm thinking to change to other function.

[Benjamin Thompson]

If this answer was helpful please mark it as accepted.