Real-Time Workshop

Workspace I/O Options and Data Logging

This section discusses several different methods by which a Real-Time Workshop generated program can save data to a MAT-file for later analysis. These methods include

• Using the Workspace I/O pane to define and log workspace return variables
• Logging data from Scope and To Workspace blocks
• Logging data using To File blocks

Tutorial 2: Data Logging of the Real-Time Workshop Getting Started Guide is an exercise designed to give you hands-on experience with data logging features of Real-Time Workshop.

Note    Data logging is available only for targets that have access to a file system.

Logging States, Time, and Outputs via the Workspace I/O Pane

The Workspace I/O pane enables a generated program to save system states, outputs, and simulation time at each model execution time step. The data is written to a MAT-file, named (by default) model.mat.

Before using this data logging feature, you should learn how to configure a Simulink model to return output to the MATLAB workspace. This is discussed in the Simulink documentation.

For each workspace return variable that you define and enable, Real-Time Workshop defines a MAT-file variable. For example, if your model saves simulation time to the workspace variable tout, your generated program will log the same data to a variable named (by default) rt_tout.

Real-Time Workshop logs the following data:

• All root Outport blocks

• The default MAT-file variable name for system outputs is rt_yout.

  The sort order of the rt_yout array is based on the port number of the Outport block, starting with 1.

• All continuous and discrete states in the model

• The default MAT-file variable name for system states is rt_xout.

• Simulation time

• The default MAT-file variable name for simulation time is rt_tout.

Real-Time Workshop data logging follows the Workspace I/O Save options: (Limit data points, Decimation, and Format).

Overriding the Default MAT-File Name.   The MAT-file name defaults to model.mat. To specify a different filename:

1. Choose Simulation parameters from the Simulation menu. The dialog box opens. Click the Real-Time Workshop tab.
2. Append the following option to the existing text in the Make command field.

• OPTS="-DSAVEFILE=filename"
  

Overriding Default MAT-File Variable Names.   By default, Real-Time Workshop prepends the string rt_ to the variable names for system outputs, states, and simulation time to form MAT-file variable names. To change this prefix:

1. Choose Simulation parameters from the Simulation menu. The dialog box opens. Click the Real-Time Workshop tab.
2. Select the target-specific code generation options item from the Category menu.
3. Select a prefix(rt_) or suffix (_rt) from the MAT-file variable name modifier field, or choose none for no prefix.

Logging Data with Scope and To Workspace Blocks

Real-Time Workshop also logs data from these sources:

• All Scope blocks that have the save data to workspace option enabled

• You must specify the variable name and data format in each Scope block's dialog box.

• All To Workspace blocks in the model

• You must specify the variable name and data format in each To Workspace block's dialog box.

The variables are written to model.mat, along with any variables logged from the Workspace I/O pane.

Logging Data with To File Blocks.   You can also log data to a To File block. The generated program creates a separate MAT-file (distinct from model.mat) for each To File block in the model. The file contains the block's time and input variable(s). You must specify the filename, variable name(s), decimation, and sample time in the To File block's dialog box.

Note that the To File block cannot be used in DOS real-time targets because of limitations of the DOS target.

Data Logging Differences in Single- and Multitasking Models

When logging data in singletasking and multitasking systems, you will notice differences in the logging of

• Noncontinuous root Outport blocks
• Discrete states

In multitasking mode, the logging of states and outputs is done after the first task execution (and not at the end of the first time step). In singletasking mode, Real-Time Workshop logs states and outputs after the first time step.

See Data Logging In Singletasking and Multitasking Model Execution for more details on the differences between single- and multitasking data logging.

Note    The rapid simulation target (rsim) provides enhanced logging options. See Real-Time Workshop Rapid Simulation Target for more information.

Solver Options

Diagnostics Pane Options