Set Up and Configure Model

This example shows how data generated by a copy of the model slexAircraftExample is logged to the file myAircraftExample.mat. Refer to Build Process Workflow for Real-Time Systems for instructions on setting up a copy of slexAircraftExample as myAircraftExample in a working folder if you have not done so already.

To configure data logging, open the Configuration Parameters dialog box and select the Data Import/Export pane. The process is the same as configuring a Simulink model to save output to the MATLAB^® workspace. For each workspace return variable you define and enable, the Simulink Coder software defines a parallel MAT-file variable. For example, if you save simulation time to the variable tout, your generated program logs the same data to a variable named rt_tout. You can change the prefix rt_ to a suffix (_rt), or eliminate it entirely. You do this by setting model configuration parameter MAT-file variable name modifier.

To log signals in generated code, use the Data Import/Export model configuration parameters described below or include To File or To Workspace blocks in your model.

Warning: MAT-file logging does not support signal logging.
When your model code executes, the signal logging variable 'rt_logsout' will
not be saved to the MAT-file. 

In this example, you modify the myAircraftExample model so that the generated program saves the simulation time and system outputs to the file myAircraftExample.mat. Then you load the data into the base workspace and plot simulation time against one of the outputs. The myAircraftExample model should be configured as described in Build Process Workflow for Real-Time Systems.

Data Logging During Simulation

To use the data logging feature:

Data Logging from Generated Code

In the second part of this example, you build and run an executable program built by the code generator for model myAircraftExample. The program outputs a MAT-file containing the simulation time and output you previously examined. Even though you have already generated code for the myAircraftExample model, you must now regenerate that code because you have changed the model by enabling data logging. The steps below explain this procedure.

To avoid overwriting workspace data with data from simulation runs, the code generator modifies identifiers for variables logged by Simulink. You can control these modifications.

Override Default MAT-File Variable Names

By default, the code generator prefixes the text rt_ to the variable names for system outputs, states, and simulation time to form MAT-file variable names. To change this prefix for a model, set model configuration parameter MAT-file variable name modifier to (rt_), a suffix (_rt), or no modifier (none). Other system target files might not support this parameter.

Override Default MAT-File Name or Buffer Size

You can specify compiler options to override the following MAT-file attributes in generated code:

For a template makefile (TMF) based target, set model configuration parameter Make command to the compiler option. For example:

For a toolchain-based system target file such as GRT or ERT, add the compiler option to model configuration. Set parameter Build configuration to Specify, and add the compiler option to the C Compiler row of the Tool/Options table. For example:

To add the compiler option to a custom toolchain, you can modify and reregister the custom toolchain using the procedures shown in the example Add Custom Toolchains to MATLAB® Coder™ Build Process. For example, to add the compiler option to the MATLAB source file for the custom toolchain, you could define myCompilerOpts as follows:

optimsOffOpts    = {'/c /Od'};
optimsOnOpts     = {'/c /O2'};
cCompilerOpts    = '$(cflags) $(CVARSFLAG) $(CFLAGS_ADDITIONAL)';
cppCompilerOpts  = '$(cflags) $(CVARSFLAG) $(CPPFLAGS_ADDITIONAL)';
myCompilerOpts   = {' -DSAVEFILE=myCodeLog.mat '};
...

Then you can add myCompilerOpts to the flags for each configuration and compiler to which it applies, for example:

cfg = tc.getBuildConfiguration('Faster Builds');
cfg.setOption('C Compiler', horzcat(cCompilerOpts, myCompilerOpts, optimsOffOpts));

As shown in Add Custom Toolchains to MATLAB® Coder™ Build Process, after modifying the custom toolchain, you save the configuration to a MAT-file and refresh the target registry.