How do I create a bus object from a struct in my workspace using Simulink 7.4 (R2009b)?

I have a structure with different datatypes in my workspace, which I want to use as a bus in Simulink. For example:

 

myStruct.firstField = [1 2 3];
myStruct.secondField = uint8(17);
myStruct.thirdField = 5;

Now, I want to be able to import this data into Simulink in a bus. I can import my data using constant blocks, which directly refer to fields of the structure and create a bus with these blocks. However, that is a lot of work.

Answer 1

[MathWorks Support Team]

This can be accomplished by creating a bus object with a script and using an Embedded MATLAB Fcn block in Simulink to output data into this bus.

Here is how this can be done:

• Attached file createTestStruct.m generates a simple structure, a, in the MATLAB workspace as an example with different datatypes
• Attached file struct2bus.m generates a Simulink Bus Object based upon the fields and datatypes in the structure
• Attached file busobject2_ex.mdl is a Simulink model including an Embedded MATLAB Fcn block that uses the data from the structure to feed a bus

In order to run the example:

1. Download the attachments (located at the bottom of the page) in a single directory.

2. Run the file createTestStruct.m to create a test structure.

3. Open and run busobject2_ex.mdl to see the result.

Here is how it works:

• At initialization of the model the struct2bus function is called to convert the structure to a Bus Object called mybus:

1. Right-click the Embedded MATLAB Fcn block.

2. Select 'Block properties...'

3. Select the 'Callbacks' tab

4. Choose 'InitFcn', which now reads "struct2bus(a,'mybus')"

• The output of the Embedded MATLAB Fcn block is linked to a Bus Object of type mybus:

1. Open the Embedded MATLAB Fcn block by double clicking it

2. Choose 'Edit Data/Ports' from the Tools menu

3. Select Output port 1

4. Choose 'Type', "Bus: bus object name"

5. Click on the Data type assistant button (>>)

6. Fill out the name of the Bus Object

• Structures in Embedded MATLAB Fcn blocks are automatically converted to Bus Objects, which property is used in this example