coder.FixPtConfig Class

Namespace: coder

Floating-point to fixed-point conversion configuration object

Description

A coder.FixptConfig object contains the configuration parameters that the MATLAB^® Coder™ codegen function requires to convert floating-point MATLAB code to fixed-point MATLAB code during code generation. Use the -float2fixed option to pass this object to the codegen function.

Creation

fixptcfg = coder.config('fixpt') creates a coder.FixPtConfig object for floating-point to fixed-point conversion.

Properties

ComputeDerivedRanges — Enable derived range analysis

false (default) | true

Enable derived range analysis, specified as true or false.

ComputeSimulationRanges — Enable collection and reporting of simulation range data

true (default) | false

Enable collection and reporting of simulation range data, specified as true or false. If you need to run a long simulation to cover the complete dynamic range of your design, consider disabling simulation range collection and running derived range analysis instead.

DefaultFractionLength — Default fixed-point fraction length

4 (default) | positive integer

Default fixed-point fraction length, specified as a positive integer.

DefaultSignedness — Default signedness of variables in the generated code

'Automatic' (default) | 'Signed' | 'Unsigned'

Default signedness of variables in the generated code, specified as 'Automatic', 'Signed', or 'Unsigned'.

DefaultWordLength — Default fixed-point word length

14 (default) | positive integer

Default fixed-point word length, specified as a positive integer.

DetectFixptOverflows — Enable detection of overflows using scaled doubles

false (default) | true

Enable detection of overflows using scaled doubles, specified as true or false.

fimath — fimath properties to use for conversion

fimath('RoundingMethod','Floor','OverflowAction','Wrap','ProductMode','FullPrecision','SumMode','FullPrecision') (default) | fimath object

fimath properties to use for conversion, specified as a fimath (Fixed-Point Designer) object.

FixPtFileNameSuffix — Suffix for fixed-point file names

'_fixpt' (default) | string

Suffix for fixed-point file names, specified as a string.

LaunchNumericTypesReport — View the numeric types report after the software has proposed fixed-point types

true (default) | false

View the numeric types report after the software has proposed fixed-point types, specified as true or false.

LogIOForComparisonPlotting — Enable simulation data logging to plot the data differences introduced by fixed-point conversion

true (default) | false

Enable simulation data logging to plot the data differences introduced by fixed-point conversion, specified as true or false.

OptimizeWholeNumber — Optimize the word lengths of variables that are always whole numbers

true (default) | false

Optimize the word lengths of variables whose simulation min/max logs indicate that they are always whole numbers, specified as true or false.

PlotFunction — Name of function to use for comparison plots

'' (default) | string

Name of function to use for comparison plots.

LogIOForComparisonPlotting must be set to true to enable comparison plotting. This option takes precedence over PlotWithSimulationDataInspector.

The plot function should accept three inputs:

• A structure that holds the name of the variable and the function that uses it.

• A cell array to hold the logged floating-point values for the variable.

• A cell array to hold the logged values for the variable after fixed-point conversion.

PlotWithSimulationDataInspector — Use the Simulation Data Inspector for comparison plots

false (default) | true

Use the Simulation Data Inspector for comparison plots, specified as true or false.

LogIOForComparisonPlotting must be set to true to enable comparison plotting. The PlotFunction option takes precedence over PlotWithSimulationDataInspector.

ProposeFractionLengthsForDefaultWordLength — Propose fixed-point types based on DefaultWordLength

true (default) | false

Propose fixed-point types based on DefaultWordLength, specified as true or false.

ProposeTargetContainerTypes — Whether to propose target container types

false (default) | true

By default (false), propose data types with the minimum word length needed to represent the value. When set to true, propose data type with the smallest word length that can represent the range and is suitable for C code generation ( 8, 16, 32, 64, … ). For example, for a variable with range [0..7], propose a word length of 8 rather than 3.

ProposeWordLengthsForDefaultFractionLength — Propose fixed-point types based on DefaultFractionLength

false (default) | true

Propose fixed-point types based on DefaultFractionLength, specified as true or false.

ProposeTypesUsing — Propose data types based on simulation range data, derived ranges, or both

'BothSimulationAndDerivedRanges' (default) | 'SimulationRanges' | 'DerivedRanges'

Propose data types based on simulation range data, derived ranges, or both, specified as 'BothSimulationAndDerivedRanges', 'SimulationRanges', or 'DerivedRanges'.

SafetyMargin — Safety margin percentage by which to increase the simulation range when proposing fixed-point types

0 (default) | real number greater than -100

Safety margin percentage by which to increase the simulation range when proposing fixed-point types, specified as a real number greater than -100.

Data Types: double

StaticAnalysisQuickMode — Perform faster static analysis

false (default) | true

Perform faster static analysis, specified as true or false.

StaticAnalysisTimeoutMinutes — Abort analysis if timeout is reached

'' (default) | positive integer

Abort analysis if timeout is reached, specified as a positive integer.

TestBenchName — Test bench function name or names

'' (default) | string | cell array of strings

Test bench function name or names, specified as a string or cell array of strings. You must specify at least one test bench. If you do not explicitly specify input parameter data types, the conversion uses the first test bench function to infer these data types.

Data Types: string | cell

TestNumerics — Enable numerics testing

false (default) | true

Enable numerics testing, specified as true or false.

Methods

Public Methods

addApproximation (Fixed-Point Designer)	Replace floating-point function with lookup table during fixed-point conversion
addDesignRangeSpecification (Fixed-Point Designer)	Add design range specification to parameter
addFunctionReplacement (Fixed-Point Designer)	Replace floating-point function with fixed-point function during fixed-point conversion
addTypeSpecification (Fixed-Point Designer)	Specify fixed-point data type for a variable during fixed-point conversion
clearDesignRangeSpecifications (Fixed-Point Designer)	Clear all design range specifications
getDesignRangeSpecification (Fixed-Point Designer)	Get design range specifications for parameter
hasDesignRangeSpecification (Fixed-Point Designer)	Determine whether parameter has design range
removeDesignRangeSpecification (Fixed-Point Designer)	Remove design range specification from parameter

Examples

Generate Fixed-Point C Code from Floating-Point MATLAB Code

This example shows how to convert a floating-point MATLAB function to fixed-point C code.

Create a coder.FixPtConfig object, fixptcfg, with default settings.

fixptcfg = coder.config('fixpt');

Set the test bench name. In this example, the test bench function name is dti_test.

fixptcfg.TestBenchName = 'dti_test';

Create a code generation configuration object to generate a standalone C static library.

cfg = coder.config('lib');

Convert a floating-point MATLAB function to fixed-point C code. In this example, the MATLAB function name is dti.

codegen -float2fixed fixptcfg -config cfg dti

Convert Floating-Point MATLAB Code to Fixed Point Based on Derived Ranges

This example shows how to convert a floating-point MATLAB function to fixed-point MATLAB code.

Create a coder.FixPtConfig object, fixptcfg, with default settings.

fixptcfg = coder.config('fixpt');

Set the name of the test bench to use to infer input data types. In this example, the test bench function name is dti_test. The conversion process uses the test bench to infer input data types.

fixptcfg.TestBenchName = 'dti_test';

Select to propose data types based on derived ranges.

fixptcfg.ProposeTypesUsing = 'DerivedRanges';
fixptcfg.ComputeDerivedRanges = true;

Add design ranges. In this example, the dti function has one scalar double input, u_in. Set the design minimum value for u_in to -1 and the design maximum to 1.

fixptcfg.addDesignRangeSpecification('dti','u_in',-1.0,1.0);

Convert the floating-point MATLAB function, dti, to fixed-point MATLAB code.

codegen -float2fixed fixptcfg dti

Enable Overflow Detection

When you select to detect potential overflows, codegen generates a scaled double version of the generated fixed-point MEX function. Scaled doubles store their data in double-precision floating-point, so they carry out arithmetic in full range. They also retain their fixed-point settings, so they are able to report when a computation goes out of the range of the fixed-point type.

Create a coder.FixPtConfig object, fixptcfg, with default settings.

fixptcfg = coder.config('fixpt');

Set the test bench name. In this example, the test bench function name is dti_test.

fixptcfg.TestBenchName = 'dti_test';

Enable numerics testing with overflow detection.

fixptcfg.TestNumerics = true;
fixptcfg.DetectFixptOverflows = true;

Create a code generation configuration object to generate a standalone C static library.

cfg = coder.config('lib');

Convert a floating-point MATLAB function to fixed-point C code. In this example, the MATLAB function name is dti.

codegen -float2fixed fixptcfg -config cfg dti

Alternatives

You can convert floating-point MATLAB code to fixed-point code using the MATLAB Coder app. Open the app using one of these methods:

• On the Apps tab, in the Code Generation section, select MATLAB Coder.

• Use the coder command.

See Convert MATLAB Code to Fixed-Point C Code.

Version History

Introduced in R2014b