Comments on: Bus Objects and Interface Specifications

By: Jane Case

Jane Case — Wed, 09 Jun 2010 22:20:47 +0000

Hi Seth,
i’ve been paying close attention to your blogs on the using bus objects in simulink and we have made good use of these to clean up the simulation and force ICD compliance. I do have a question however we use non-virtual bus signals output to the top level of the simulation s.t. when we generate code we can have other software use the structures that are created. We are now trying to log the data output by generated executable and are wanting to use the built in data logging that Matlab provides. However when i try to generate code and have a bus signal connected to an output while having signal logging enabled i get an error: “Logging non build-in data type is not supported. Cannot log outport ‘simserver/Eng_SigOut_bus’ with data type Eng_SigOut; one solution is to disable data logging”
Is there a way to be able to use the logging feature while bus signals are connected to out ports? We know that we can log all signals if we split them out from the bus, but that defeats the purpose of using non-virtual buses… Hope you can help.
Thanks!

By: garla

garla — Thu, 05 Nov 2009 11:13:36 +0000

what is advantage of exporting the bus object with the format as “cell” and “object”. what is the difference between them?

By: Tyler

Tyler — Fri, 26 Sep 2008 21:44:19 +0000

Seth,
I find this discussion helpful, and I would like to ask for further elaboration on Doug’s question about transformations between matlab structs and a non-virtual bus object. I read your response regarding an instance versus a specification. What I would like to be able to do is to avoid buses entirely and have structs be passed as outputs of embedded matlab blocks into other blocks that inherit the type. This doesn’t work, and so it seems that I am forced to make bus objects. Unfortunately, I don’t find an easy way to automatically generate bus objects from these structs (which I would like to edit inside the embedded matlab code). Any clarification is welcome – thanks in advance. -Tyler

By: Maarten

Maarten — Tue, 26 Aug 2008 10:13:10 +0000

Seth,

As far as I can gather, it is not possible to stream data created using signal logging of a virtual bus to an Input port of another model. Could you comment on this?

I would like to avoid the non-virtual bus stuff since it sounds too much hassle for a medium sized project and I want to keep my diagrams clean (i.e. just press play)

By: Seth

Seth — Fri, 18 Jul 2008 03:18:32 +0000

@Doug – I have had many people ask about such a conversion tool. The challenge comes from the variety of types and syntax requirements that C/C++ allow which do not easily map back to Bus Objects. If you write such a tool, please share it on the File Exchange!

Regarding the MATLAB struct and the Bus Object, consider that there is a difference in what these two things are. The Bus Object is a specification, and the struct is an instance. They are similar, but Bus Objects have no values associated with their elements. Simulink.Timeseries and Simulink.TSArray provide a method for specifying the value of a bus signal for inputs to a model.

By: Doug Forman

Doug Forman — Wed, 09 Jul 2008 22:20:59 +0000

Also,
Is there any relationship possible between a matlab struct and a non-virtual bus object?
Is there a simple transformation between the matlab struct and a non-virtual bus object?

By: Doug Forman

Doug Forman — Wed, 09 Jul 2008 21:04:00 +0000

Seth,
Have you heard of a script (perl or matlab) that can create a Matlab bus object from a C struct definition, (or C++ class definition)?
I am using legacy_code to import several different C functions that access (by reference) global data structures.
Each C function will become a separate S-Function and therefore can’t see global variables declared by the other S-Functions. I am now wanting to convert the C data structures to matlab bus objects that can be accessed by the separate S-Functions.
Thanks ~ Doug

By: Seth

Seth — Fri, 06 Jun 2008 23:38:43 +0000

@Guilherme Dedecca - Excellent use of a bus for interface specification! There is a technical support solution about how to create a Simulink.TsArray. It contains a simple example. There is also a nice file exchange submission from Robyn Jackey that demonstrates how this is done with a nested bus. The helper functions in that file really simplify the process of creating the Simulink TS Arrays.

By: Guilherme Dedecca

Guilherme Dedecca — Fri, 06 Jun 2008 21:15:53 +0000

Hello Seth!

I’ve been developing a model and I started using Bus Objects at the root-level inputs to specify the signals they are expected to receive. By doing this, I could propagate the expected signals at root-level Inputs to the rest of the model and use them at Bus Selectors, for exemple.

The time has come to simulate the model, and I wanted to use the Data Import/Export feature to apply several test cases to the inputs of the model. But, as far as I could find, the only way to import data to Inports that use Bus Objects is if the data is packed into an Simulink.TSArray object. The problem is that I didn’t find another way to create an Simulink.TSArray object other than to log the signals from a previous simulation and import this logged data back into the model through Data Import/Export.

Is there another way to import Data to Inports that use Bus Objects?

Thank you!

By: Justin Mellor

Justin Mellor — Thu, 08 May 2008 10:20:58 +0000

Seth,
I have just ‘tuned in’ to this discussion about bus signals. As I am in the process of integrating a large mode using Model References for all the major components of the system, this is highly relevant. I definitely need to lock down the interfaces to the different components – these are being developed across multiple sites in accordance with an Interface Control Document that we have produced.
I have a question:
The interconnects between our components are a mixture of busses and individual signal lines. I can use Simulink.Signal objects to define the characteristics of these individual signals, creating them using the Model Explorer, however, I don’t know how to save these signals as M-files (there does not appear to be an equivalent to Simulink.Bus.save for signal objects). Saving the objects as M-files rather than MAT-files gives us the option to look at the files and edit them.

Regards

Justin Mellor