Access Simulink Bus Signals in MATLAB Functions
This example shows how to read from and write to Simulink® bus signals in a MATLAB® function by using MATLAB and Stateflow® structures. MATLAB structures enable you to bundle data of different sizes and types into a single variable. You can create a MATLAB structure to:
Store related data in a local or persistent variable of a MATLAB function
Read from or write to a local Stateflow structure
Interface with a Simulink bus signal at an input or output port
MATLAB functions support nonvirtual buses only. For more information, see Composite Interface Guidelines (Simulink).
Define Structures in MATLAB Functions
In this example, a Stateflow chart processes data from one Simulink bus signal and outputs the result to another Simulink bus signal. Both the input and output bus signals are defined by the Simulink.Bus
(Simulink) object BusObject
. These buses have four fields: sb
, a
, b
, and c
. The field sb
is also a bus signal defined by the Simulink.Bus
object SubBus
. It has one field called ele
.
In the chart, the Simulink bus signals interface with the Stateflow structures in
and out
. The function sb2abc
extracts information from the input structure and stores it in the local Stateflow structure localbus
. Then the chart writes to the output structure by combining the values of the local structure and one of the elements of the array of structures subBusArray
. For more information on accessing and modifying the contents of a Stateflow structure or an array of Stateflow structures, see Index and Assign Values to Stateflow Structures.
The MATLAB® function sb2abc
takes a Stateflow structure of type SubBus
and returns a Stateflow structure of type BusObject
. The function decomposes the value of the field ele
from its input into three components: a vector, a 3-by-2 matrix, and a scalar. The function stores these components in a local MATLAB
that has the same fields as the struct
Simulink.Bus
object BusObject
. Then the function assigns the value of the MATLAB struct
to the output structure y
.
function y = sb2abc(u)
% extract data from input structure
A = double(u.ele(1:2,1)); B = uint8(u.ele(:,2:3)); C = double(u.ele(3,1));
% create local structure
X = struct(ele=int8(zeros(3))); Y = struct(sb=X,a=A,b=B,c=C);
% assign value to output structure
y = Y;
end
Define Input and Output Structures
In a MATLAB function, you can access a local Stateflow structure or interface with a Simulink bus signal by defining the input and output structures for the function:
In the base workspace, create a
Simulink.Bus
object that defines the structure data type.In the Symbols pane, select the function input or output.
In the Property Inspector, set the Type property to
Bus: <object name>
. Replace <object name> with the name of theSimulink.Bus
object that defines the Stateflow structure.
For example, in the function sb2abc
:
The Type property of the input structure
u
is specified asBus: SubBus
.The Type property of the output structure
y
is specified asBus: BusObject
.
For more information, see Define Stateflow Structures.
Define Local and Persistent Structure Variables
To store related data in a single variable inside a MATLAB function, you can create a MATLAB struct
as a local or persistent variable. For example, the function sb2abc
defines two local MATLAB structures to temporarily store the data extracted from the input structure u
before writing to the output structure y
:
X
is a scalarstruct
with a single field calledele
. This field contains a 3-by-3 matrix of typeint8
, which matches the structure of theSimulink.Bus
objectSubBus
.Y
is a scalarstruct
with four fields:sb
is a substructure of typeSubBus
,a
is a two-dimensional vector of typedouble
,b
is a 3-by-2 matrix of typeuint8
, andc
is a scalar of typedouble
. These fields match the structure of theSimulink.Bus
objectBusObject
.
For more information, see Define Scalar Structures for Code Generation (Simulink).
See Also
struct
| Simulink.Bus
(Simulink)