This example shows how to use the Fixed-Point Tool to convert a model containing a MATLAB® Function block to fixed point.
Do not edit the fixed-point variant of your MATLAB Function block algorithm. Use the code view to edit the floating-point variant of your MATLAB code and repropose and apply data types.
For a successful conversion, only use modeling constructs supported by the Fixed-Point Converter app. For a list of the supported modeling constructs, see MATLAB Language Features Supported for Automated Fixed-Point Conversion.
While collecting range information, do not edit the MATLAB code in the MATLAB Function block. Editing the code will cause problems if you try to merge results.
During the fixed-point conversion process using the Fixed-Point Tool, do not use the “Save as” option to save the MATLAB Function block with a different name. If you do, you might lose existing results for the original block.
Change directories to the folder where the model is located. At the MATLAB command line, enter:
ex_symmetric_fir.slx file to a local
writable folder and open the model.
ex_symmetric_fir model uses a symmetric
FIR filter. Simulate the model and inspect the model output. Inspect
the symmetric FIR filter algorithm by double-clicking the MATLAB Function
To open the Fixed-Point Tool, from the model menu, select Analysis > Data Type Design > Fixed-Point Tool.
In the Prepare System for Conversion section of the
toolstrip, under System under design, select the
symmetric_fir subsystem, which contains the
MATLAB Function block, as the system to convert.
Collect idealized ranges to use for data type proposal.
In the Collect Ranges section of the toolstrip, select Simulation Ranges as the method of range collection. This button configures the model to collect ranges using idealized floating-point data types.
Click the Collect Ranges button to start the simulation
The Fixed-Point Tool stores the simulation data in a run titled
(Double). Examine the range information of the MATLAB variables in the spreadsheet.
Configure the proposal settings and propose fixed-point data types for the model.
In the Convert Data Types section of the toolstrip you can configure the data type proposal settings for the MATLAB Function block variables.
In this example, use the default proposal settings.
Click Propose Data Types.
The data type proposals appear in the ProposedDT column of the spreadsheet.
The SpecifiedDT column is always blank for MATLAB Function block variables.
To launch the code view, click the MATLAB Functions button.
Using the code view you can:
View detailed variable and expression information.
Adjust proposal settings, such as
Edit proposed data types.
Manage function replacements.
For examples showing how to replace MATLAB functions with a lookup table, see Replace Functions in a MATLAB Function Block with a Lookup Table.
Edit your code.
Propose fixed-point data types.
Apply proposed data types to your code.
To view the current proposal settings, click Settings.
Here you can edit the
fimath properties for the
function. For this example, the default
When you have finished examining the proposed types, editing proposal settings, and implementing any function replacements, apply the proposed data types to the model. You can apply the data types either from the code view, or from the Fixed-Point Tool.
In the code view window, click Apply. The left pane displays both the original floating-point MATLAB Function block, as well as a newly generated fixed-point variant MATLAB Function block.
Right-click on the MATLAB Function block node in the left
Go to Block to navigate to
the MATLAB Function block in the model.
A variant subsystem is now in the place of the MATLAB Function block. The variant subsystem contains both floating-point and fixed-point versions of the MATLAB Function block. The active version is automatically controlled by the Fixed-Point Tool based on the data type override settings of the model. Data Type Override is not currently active on the model, so the fixed-point version is active.
Return to the Fixed-Point Tool to verify the results of the conversion.
In the Verify section of the toolstrip, click the Simulate with Embedded Types button to simulate the model using the newly applied fixed-point data types. The model simulates with the fixed-point variant as the active variant.