HDL Code Generation from System Objects

This example shows how to generate HDL code from MATLAB® code that contains System objects.

MATLAB Design

The MATLAB code used in this example implements a simple symmetric FIR filter and uses the dsp.Delay System object to model state. This example also shows a MATLAB test bench that exercises the filter.

design_name = 'mlhdlc_sysobj_ex';
testbench_name = 'mlhdlc_sysobj_ex_tb';

Let us take a look at the MATLAB design.

type(design_name);

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% MATLAB design: Symmetric FIR Filter
% 
% Design pattern covered in this example: 
%  Filter states modeled using DSP System object (dsp.Delay)
%  Filter coefficients passed in as parameters to the design
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

%   Copyright 2011-2015 The MathWorks, Inc.

%#codegen
function [y_out, delayed_xout] = mlhdlc_sysobj_ex(x_in, h_in1, h_in2, h_in3, h_in4)
% Symmetric FIR Filter

persistent h1 h2 h3 h4 h5 h6 h7 h8;
if isempty(h1)
    h1 = dsp.Delay;
    h2 = dsp.Delay;
    h3 = dsp.Delay;
    h4 = dsp.Delay;
    h5 = dsp.Delay;
    h6 = dsp.Delay;
    h7 = dsp.Delay;
    h8 = dsp.Delay;
end

h1p = step(h1, x_in);
h2p = step(h2, h1p);
h3p = step(h3, h2p);
h4p = step(h4, h3p);
h5p = step(h5, h4p);
h6p = step(h6, h5p);
h7p = step(h7, h6p);
h8p = step(h8, h7p);

a1 = h1p + h8p;
a2 = h2p + h7p;
a3 = h3p + h6p;
a4 = h4p + h5p;

m1 = h_in1 * a1;
m2 = h_in2 * a2;
m3 = h_in3 * a3;
m4 = h_in4 * a4;

a5 = m1 + m2;
a6 = m3 + m4;

% filtered output
y_out = a5 + a6;
% delayout input signal
delayed_xout = h8p;

end

type(testbench_name);

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% MATLAB test bench for the FIR filter
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

%   Copyright 2011-2015 The MathWorks, Inc.

clear mlhdlc_sysobj_ex;
 
x_in = cos(2.*pi.*(0:0.001:2).*(1+(0:0.001:2).*75)).';


h1 = -0.1339;
h2 = -0.0838;
h3 = 0.2026;
h4 = 0.4064;

len = length(x_in);
y_out_sysobj = zeros(1,len);
x_out_sysobj = zeros(1,len);
a = 10;

for ii=1:len
    data = x_in(ii);
    % call to the design 'sfir' that is targeted for hardware
    [y_out_sysobj(ii), x_out_sysobj(ii)] = mlhdlc_sysobj_ex(data, h1, h2, h3, h4);    
end


figure('Name', [mfilename, '_plot']);
subplot(2,1,1); 
plot(1:len,x_in); title('Input signal with noise');
subplot(2,1,2);
plot(1:len,y_out_sysobj); title('Filtered output signal');

Create a New Folder and Copy Relevant Files

Execute the following lines of code to copy the necessary example files into a temporary folder.

mlhdlc_demo_dir = fullfile(matlabroot, 'toolbox', 'hdlcoder', 'hdlcoderdemos', 'matlabhdlcoderdemos');
mlhdlc_temp_dir = [tempdir 'mlhdlc_sysobj_intro'];

% Create a temporary folder and copy the MATLAB files.
cd(tempdir);
[~, ~, ~] = rmdir(mlhdlc_temp_dir, 's');
mkdir(mlhdlc_temp_dir);
cd(mlhdlc_temp_dir);

copyfile(fullfile(mlhdlc_demo_dir, [design_name,'.m*']), mlhdlc_temp_dir);
copyfile(fullfile(mlhdlc_demo_dir, [testbench_name,'.m*']), mlhdlc_temp_dir);

Simulate the Design

Simulate the design with the test bench prior to code generation to make sure there are no runtime errors.

mlhdlc_sysobj_ex_tb

Create a New HDL Coder™ Project

To create a new project, enter the following command:

coder -hdlcoder -new mlhdlc_sysobj_prj

Next, add the file 'mlhdlc_sysobj_ex.m' to the project as the MATLAB Function and 'mlhdlc_sysobj_ex_tb.m' as the MATLAB Test Bench.

Refer to Getting Started with MATLAB to HDL Workflow for a more complete tutorial on creating and populating MATLAB HDL Coder projects.

Run Fixed-Point Conversion and HDL Code Generation

Launch the Workflow Advisor. In the Workflow Advisor, right-click the 'Code Generation' step. Choose the option 'Run to selected task' to run all the steps from the beginning through HDL code generation.

Examine the generated HDL code by clicking the links in the log window.

Supported System objects

For a list of System objects supported for HDL code generation, see Predefined System Objects Supported for HDL Code Generation.

Clean up the Generated Files

Run the following commands to clean up the temporary project folder.

mlhdlc_demo_dir = fullfile(matlabroot, 'toolbox', 'hdlcoder', 'hdlcoderdemos', 'matlabhdlcoderdemos');
mlhdlc_temp_dir = [tempdir 'mlhdlc_sysobj_intro'];
clear mex;
cd (mlhdlc_demo_dir);
rmdir(mlhdlc_temp_dir, 's');

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