Tunable Workspace Parameter Data Type Considerations
If you are using tunable workspace parameters, you need to be
aware of potential issues regarding data types. A workspace parameter
is tunable when the following conditions exist:
When generating code for tunable workspace parameters, the Real-Time Workshop product
checks and compares the data types used for a particular parameter
in the workspace and in Block Parameter dialog boxes.
| If... | The Real-Time Workshop Product... |
|---|
| The data types match | Uses that data type for the parameter in the generated code. |
| You do not explicitly specify a data type other than double in
the workspace | Uses the data type specified by the block in the generated
code. If multiple blocks share a parameter, they must all specify
the same data type. If the data type varies between blocks, the product
generates an error similar to the following:Variable 'K' is used in incompatible ways
in the dialog fields of the following:
cs_params/Gain, cs_params/Gain1. The
variable'value is being used both directly
and after a transformation. Only one of
these usages is permitted for any given
variable. |
| You explicitly specify a data type other than double in
the workspace | Uses the data type from the workspace for the parameter. The
block typecasts the parameter to the block specific data type before
using it. |
Guidelines for Specifying Data Types
The following table provides guidelines on specifying data types
for tunable workspace parameters.
| If You Want to... | Then Specify Data Types in... |
|---|
| Minimize memory usage (int8 instead of single) | The workspace explicitly |
| Avoid typecasting | Blocks only |
| Interface to legacy or custom code | The workspace explicitly |
| Use the same parameter for multiple blocks that specify different
data types | The workspace explicitly |
The Real-Time Workshop product enforces limitations on the
use of data types other than double in the workspace,
as explained in Limitations on Specifying Data Types in the Workspace Explicitly.
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Limitations on Specifying Data Types in the Workspace Explicitly
When you explicitly specify a data type other than double in
the workspace, blocks typecast the parameter to the appropriate data
type. This is an issue for blocks that use pointer access for their
parameters. Blocks cannot use pointer access if they need to typecast
the parameter before using it (because of a data type mismatch). Another
case in which this occurs is for workspace variables with bias or
fractional slope. Two possible solutions to these problems are
Remove the explicit data type specification in the
workspace for parameters used in such blocks.
Modify the block so that it uses the parameter with
the same data type as specified in the workspace. For example, the
Lookup Table block uses the data types of its input signal to determine
the data type that it uses to access the X-breakpoint parameter.
You can prevent the block from typecasting the run-time parameter
by converting the input signal to the data type used for X-breakpoints in
the workspace. (Similarly, the output signal is used to determine
the data types used to access the lookup table's Y data.)
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 | Generated Code for Parameter Data Types | | Parameter Tuning by Using MATLAB Commands |  |
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