MATLAB: Simulink.Bus and Embedded Coder

Embedded Coderstructures

I have a few Matlab files that work correctly and implement the functionality I need. I am now trying to port them to Simulink/Embedded Coder using the "Matlab Function" block. After resolving a number of "not supported" type problems, I am stuck on a problem that I don't know how to resolve.

The issue is this- the Matlab functions use a structure to keep track of the system state. They modify the state and pass it on to each other. Embedded Coder indicated that structs were not supported, so I added the following line that I found in a Matlab blog post- "outputState = Simulink.Bus.createObject(state);"

That seemed to improve things in that Embedded Coder got "farther". Now, though, it says the following- "Function 'Simulink.Bus' is not supported for code generation. Consider adding coder.extrinsic('Simulink.Bus') at the top of the function to bypass code generation." I tried adding the extrinsic, but it just came up with another error.

Can you use structs in Embedded Coder? If so, what do I need to do. I could break the state struct into individual values/arrays, but it would be very ugly and painful. Thanks for your time and help.

Best Answer

You need to specify the Bus type on the Ports and Data Manager of the MATLAB Function block, not in the MATLAB code itself. Please see Attach Bus Signals to MATLAB Function Blocks.

Related Solutions

MATLAB: How to enable support for variable-size data in Simulink 7.7 (R2011a)

The support for dynamic matrices could be enabled by checking the option"Support Variable-Size Arrays" in Model Explorer.

Please refer to the section "Enabling Support for Variable-Size Data" in the following location:

http://www.mathworks.com/help/releases/R2011b/toolbox/simulink/ug/br9_55w.html

MATLAB: How to create an output bus with variable-size elements using a structure in Embedded MATLAB

To create a variable size bus using the command line, use the following steps:

- Create a bus element that is varsized.

1. Create a bus element using the Simulink.BusElement object. For more information consult the following documentation at the MATLAB Command prompt in MATLAB 7.10 (R2010a):

      web([docroot '/toolbox/simulink/slref/simulink.buselement.html#bqqmehe-1'])

2. After specifying other properties of the bus element, such as name etc., set the following properties of the bus element:

a. Dimensions - use an array that specifies the dimension of this bus element. This is the maximum dimension.

b. DimensionsMode - 'Variable' - this will indicate that the bus element is varsized

- Add all the relevant bus element objects to a Simulink.Bus object as shown below:

      ABus_Element=Simulink.BusElement
      ABus_Element.Name='A'
      BBus_Element=Simulink.BusElement
      BBus_Element.Name='B'
      BBus_Element.DimensionsMode='Variable'
      BBus_Element.Dimensions=4 %for example
      ABus=Simulink.Bus
      ABus.Elements=[ABus_Element;BBus_Element]

To create a variable size bus using the Bus Editor, consult the following documentation at the MATLAB Command prompt in MATLAB 7.10 (R2010a):

      web([docroot '/toolbox/simulink/ug/brin2jr-1.html#brin204-4'])

The attached example model (TS_example_varsize.mdl) demonstrates how one may use a bus that contains a variable size signal. Here, the following steps were taken:

1. Two buses are created in the PostLoadFcn callback of the model:

     - InputBus - whose elements are fixed in size
     - OutputBus - whose elements are variable in size, with a maximum dimension

2. Using a BusCreator block, the input bus signal is passed to an Embedded MATLAB block.

3. Using the Embedded MATLAB block's Port and Data Manager, the input and output are set to the bus objects mentioned in step 1.

4. Within the Embedded MATLAB block 'outbus.ab_sum' is defined as a vector of 1's whose length is equal to the rounded value of one of the inputs.

5. The output bus of the Embedded MATLAB block is then passed to a Bus Selector block that allows for each bus element to be displayed individually.

Note the following features of this model:

1. The PostLoadFcn callback declares the ab_sum bus element to have 'DimensionsMode'='Variable' and a 'Dimension'= 4. This is to create a varsized bus as discussed above.

2. The input 'b' for the Embedded function MATLAB block has been used to define the length of the signal ab_sum for a given time step.

3. Line 10 of the Embedded MATLAB function block ensures that the length of the variable size signal never violates the upper bound that was established in the PreLoadFcn callback

refer to the documentation for information regarding variable-size data in Embedded MATLAB code by executing the following at the MATLAB Command prompt in MATLAB 7.10 (R2010a):

      web([docroot '/toolbox/eml/ug/br7rggy.html#br9t1u0'])
      web([docroot '/toolbox/eml/ref/eml.varsize.html'])

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