Learn how to use the Staccato™ Basic Task State Diagram and earn IEEE Continuing Education Units (CEUs)

Click here...

This tutorial will show you some basic concepts of how to construct a basic state diagram of a task. The Staccato™ Architecture requires that your embedded system software be partitioned into individual application tasks, each of which is responsible for a device interface, a communication protocol layer, or some algorithmic processing of data. An embedded application therefore becomes a 'system of directly executed Finite State Machines (FSMs)'

Each of your system tasks will be implemented as a finite state machine.

Using state diagrams to convey the behavior of a task in response to events and conditions is oftentimes regarded a difficult task in itself. However, by considering the Basic Task State Diagram Template, as shown here,  we can achieve a better understanding of how to get started with this important and necessary design process.

The state diagram template shows the four states that will likely occur in many of your task designs.

ALL tasks must have an initialization state, shown in the diagram as state 0.0 INIT. This initialization state code will be the first code executed for this task, and will likely occur immediately after system power-up and initialization. Within this state, your code will initialize any hardware devices and any task-related variables. Notice that if an error occurs during this initialization, the task will transit to state 3.0, the error state. Otherwise, execution continues in the idle state of 1.0, wait request, where the task will remain until an external request is set by another task.

When this request event occurs, the task will clear the request event, and setup the requested process, and transit to state 2.0 where the requested process is performed. The task remains in this state, performing the process action until either an error occurs, resulting in a transition to state 3.0, or the process completes successfully causing a transition back to the idle state of 1.0.
 

Although this state diagram representation of a task may seem simplistic, you should regard it as a template for each of your tasks within a Staccato™ Architecture. It is therefore recommended that you use this template to begin your designs of each of your application tasks, until you become more proficient in using state diagrams. The Staccato™ Crossroads SDK with Certified Training program provides extensive coverage of how state diagrams can be used to analyze and design both abstract and physical systems. Also, encoding your task state diagrams to generate your module source-code is a very straightforward process, especially with the assistance of the Staccato™ API System Calls.