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Software Diagramming In Embedded Systems?
afd100 writes "I work for a medium-sized company building embedded systems using C. As of yet, we do not have a great design methodology, but it is something we're working on. For the last 7 years now, we've been documenting our embedded software in an IEEE'esque Software Detailed Design, and using a very cryptic block diagram to explain our software. What does the embedded software community at large currently use to graphical represent their software or do they even try this? Since the programming is functionally decomposed, is UML the right way to go?"
Ditch your diagrams. They're far too often used to:
1) As a thing to show boss that you're working.
2) Unnecessary cruft which no one uses.
About the only case where diagrams are helpful are FSM diagrams.
I too work in embedded systems, more specifically aircraft controls. In most of our design documents we tend to keep the design to the interface level of each software component (CSC), and the interaction between them. Drawing this is usually down using more simple drawing elements than that of UML. Draw a couple of boxes to show your major components, and label the interfaces of those. In subsequent sections, show only one of the components at a time, with a drawing of its sub-components if applicable. Only go about 3 levels deep if at all possible here. The attention span of most reviews will get lost after that. Besides, your requirements already specify WHAT has to happen, your only job here is to specify WHERE those requirements happen.
While UML is nice, I have found that most of the reviewers of these types of documents are not UML savvy. The one drawing mechanism of UML that I do find invaluable in this line of work is the sequence diagrams. Large amounts of requirements can often be shown more precisely by a sequence diagram, detailing the interactions between a handful of component interfaces at a time.
Take it a step up and evaluate some modeling languages and tools, such as AADL and OSATE.
http://www.aadl.info/
This stuff is MADE for real-time, embedded systems. The ultimate goal is to use it through design and analysis, and then go ahead and generate code. It does take some getting used to, and there is a lot to it so keep that in mind.
It's not perfect, and still under development, but very cool. So give it a try, see if you can pick it up. I'm generally a supporter of UML, but after being introduced to AADL and OSATE in an architecture course I was eventually convinced that it could be better than UML for this field.
Most times when people think about using flowcharts, they really should create state transition diagrams http://en.wikipedia.org/wiki/State_diagram/ to discuss, describe, and document behavior. Statecharts are an improvement on earlier state transition diagrams and are included in the latest UML specification.
Some Statechart references: