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Reading Fixed-Point Signals from the Workspace |
You can read fixed-point data from the MATLAB^{®} workspace into a Simulink^{®} model using the Signal From Workspace and Triggered Signal From Workspace blocks from DSP System Toolbox™ software. Enter the name of the defined fi variable in the Signal parameter of the Signal From Workspace or Triggered Signal From Workspace block.
Fixed-point output from a model can be written to the MATLAB workspace via the To Workspace or Triggered To Workspace block from the blockset. The fixed-point data is always written as a 2-D or 3-D array.
Note To write fixed-point data to the MATLAB workspace as a fi object, select the Log fixed-point data as a fi object check box on the Signal To Workspace or Triggered To Workspace block dialog. Otherwise, fixed-point data is converted to double and written to the workspace as double. |
For example, you can use the following code to create a fi object in the MATLAB workspace. You can then use the Signal From Workspace block to bring the data into a Simulink model.
a = fi([sin(0:10)' sin(10:-1:0)']) a = 0 -0.5440 0.8415 0.4121 0.9093 0.9893 0.1411 0.6570 -0.7568 -0.2794 -0.9589 -0.9589 -0.2794 -0.7568 0.6570 0.1411 0.9893 0.9093 0.4121 0.8415 -0.5440 0 DataTypeMode: Fixed-point: binary point scaling Signedness: Signed WordLength: 16 FractionLength: 15
The Signal From Workspace block in the following model has these settings:
Signal — a
Sample time — 1
Samples per frame — 2
Form output after final data value by — Setting to zero
The following parameters in the Solver pane of the Model Configuration Parameters dialog have these settings:
Start time — 0.0
Stop time — 10.0
Type — Fixed-step
Solver — Discrete (no continuous states)
Fixed step size (fundamental sample time) — 1.0
Remember, to write fixed-point data to the MATLAB workspace as a fi object, select the Log fixed-point data as a fi object check box on the Signal To Workspace block dialog. Otherwise, fixed-point data is converted to double and written to the workspace as double.
The Signal To Workspace block writes the result of the simulation to the MATLAB workspace as a fi object.
yout = (:,:,1) = 0.8415 -0.1319 -0.8415 -0.9561 (:,:,2) = 1.0504 1.6463 0.7682 0.3324 (:,:,3) = -1.7157 -1.2383 0.2021 0.6795 (:,:,4) = 0.3776 -0.6157 -0.9364 -0.8979 (:,:,5) = 1.4015 1.7508 0.5772 0.0678 (:,:,6) = -0.5440 0 -0.5440 0 DataTypeMode: Fixed-point: binary point scaling Signedness: Signed WordLength: 17 FractionLength: 15
When the Arithmetic property is set to 'fixed', you can use an existing fi object as the input, states, or coefficients of a dfilt object in DSP System Toolbox software. Also, fixed-point filters in the toolbox return fi objects as outputs. Refer to the DSP System Toolbox software documentation for more information.