Overview

HDL code generation with the command-line interface has the following basic steps:

The HDL Coder command-line interface can use two coder config objects with the codegen command. The optional fixpt coder config object configures the floating-point to fixed-point conversion of your MATLAB code. The hdl coder config object configures HDL code generation and FPGA programming options.

In this example, we explore different ways you can configure your floating-point to fixed-point conversion and code generation.

The example code implements a discrete-time integrator and its test bench.

Copy the Design and Test Bench Files Into a Temporary Folder

Execute the following code to copy the design and test bench files into a temporary folder:

close all;
design_name = 'mlhdlc_dti';
testbench_name = 'mlhdlc_dti_tb';

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

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);

Basic Code Generation With Floating-Point to Fixed-Point Conversion

You can generate HDL code and convert the design from floating-point to fixed-point using the default settings.

You need only your design name, mlhdlc_dti, and test bench name, mlhdlc_dti_tb:

close all;

% Create a 'fixpt' config with default settings
fixptcfg = coder.config('fixpt');
fixptcfg.TestBenchName = 'mlhdlc_dti_tb';

% Create an 'hdl' config with default settings
hdlcfg = coder.config('hdl'); %#ok<NASGU>

After setting up fixpt and hdl config objects, run the following codegen command to perform floating-point to fixed-point conversion, and generate HDL code.

codegen -float2fixed fixptcfg -config hdlcfg mlhdlc_dti

If your design already uses fixed-point types and functions, you can skip fixed-point conversion:

hdlcfg = coder.config('hdl'); % Create an 'hdl' config with default settings
hdlcfg.TestBenchName = 'mlhdlc_dti_tb';
codegen -config hdlcfg mlhdlc_dti

The rest of this example describes how to configure code generation using the hdl and fixpt objects.

Create a Floating-Point to Fixed-Point Conversion Config Object

To perform floating-point to fixed-point conversion, you need a fixpt config object.

Create a fixpt config object and specify your test bench name:

close all;
fixptcfg = coder.config('fixpt');
fixptcfg.TestBenchName = 'mlhdlc_dti_tb';

Set Fixed-Point Conversion Type Proposal Options

The code generator can propose fixed-point types based on your choice of either word length or fraction length. These two options are mutually exclusive.

Base the proposed types on a word length of 24:

fixptcfg.DefaultWordLength = 24;
fixptcfg.ProposeFractionLengthsForDefaultWordLength = true;

Alternatively, you can base the proposed fixed-point types on fraction length. The following code configures the coder to propose types based on a fraction length of 10:

fixptcfg.DefaultFractionLength = 10;
fixptcfg.ProposeWordLengthsForDefaultFractionLength = true;

Set the Safety Margin

The code generator increases the simulation data range on which it bases its fixed-point type proposal by the safety margin percentage. For example, the default safety margin is 4, which increases the simulation data range used for fixed-point type proposal by 4%.

Set the SafetyMargin to 10%:

fixptcfg.SafetyMargin = 10;

Enable Data Logging

The code generator runs the test bench with the design before and after floating-point to fixed-point conversion. You can enable simulation data logging to plot the quantization effects of the new fixed-point data types.

Enable data logging in the fixpt config object:

fixptcfg.LogIOForComparisonPlotting = true;

View the Numeric Type Proposal Report

Configure the code generator to launch the type proposal report once the fixed-point types have been proposed:

fixptcfg.LaunchNumericTypesReport = true;

Create an HDL Code Generation Config Object

To generate code, you must create an hdl config object and set your test bench name:

hdlcfg = coder.config('hdl');
hdlcfg.TestBenchName = 'mlhdlc_dti_tb';

Set the Target Language

You can generate either VHDL or Verilog code. HDL Coder generates VHDL code by default. To generate Verilog code:

hdlcfg.TargetLanguage = 'Verilog';

Generate HDL Test Bench Code

Generate an HDL test bench from your MATLAB® test bench:

hdlcfg.GenerateHDLTestBench = true;

Simulate the Generated HDL Code Using an HDL Simulator

If you want to simulate your generated HDL code using an HDL simulator, you must also generate the HDL test bench.

Enable HDL simulation and use the ModelSim simulator:

hdlcfg.SimulateGeneratedCode = true;
hdlcfg.SimulationTool = 'ModelSim'; %  or 'ISIM'

Generate an FPGA Programming File

You can generate an FPGA programming file if you have a synthesis tool set up. Enable synthesis, specify a synthesis tool, and specify an FPGA:

% Enable Synthesis.
hdlcfg.SynthesizeGeneratedCode = true;

% Configure Synthesis tool.
hdlcfg.SynthesisTool = 'Xilinx ISE'; %  or 'Altera Quartus II';
hdlcfg.SynthesisToolChipFamily = 'Virtex7';
hdlcfg.SynthesisToolDeviceName = 'xc7vh580t';
hdlcfg.SynthesisToolPackageName = 'hcg1155';
hdlcfg.SynthesisToolSpeedValue = '-2G';

Run Code Generation

Now that you have your fixpt and hdl config objects set up, run the codegen command to perform floating-point to fixed-point conversion, generate HDL code, and generate an FPGA programming file:

codegen -float2fixed fixptcfg -config hdlcfg mlhdlc_dti