The application should switch on and off the LED for 5 seconds in a 1 second interval, than stop blinking for 5 seconds and start again. To implement this behavior we will implement two FSMs. One for the 1 second interval and one for the 5 second interval. The 1 second blinking should be implemented in [Blinky]. The 5 second interval should be implemented in [BlinkyController]. First implement the Controller.
Right click to [BlinkyController] and select [Edit Behavior]. Drag and Drop the [Initial Point] and two [States] into the top state. Name the states [on] and [off]. Use the [Transition] tool to draw transitions from [init] to [on] from [on] to [off] and from [off] to [on].
Open the transition dialog by double click the arrow to specify the trigger event and the action code of each transition. Note that the initial transition does not have a trigger event.
The transition dialog should look like this:
The defined ports will be generated as a member attribute of the actor class from type of the attached protocol. So, to send e message you must state [port.message(param);]. In this example [ControlPort.start()] sends the [start] message via the [ControlPort] to the outside world. Assuming that [Blinky] is connected to this port, the message will start the one second blinking FSM. It is the same thing with the [timer]. The SAP is also a port and follows the same rules. So it is clear that [timer.Start(5000);] will send the [Start] message to the timing service. The timing service will send a [timeoutTick] message back after 5000ms.
Within each transition the timer will be restarted and the appropriate message will be sent via the [ControlPort].
The resulting state machine should look like this: (Note that the arrows peak changes if the transition contains action code.)
Save the diagram and inspect the [Blinky.room] file. The [BlinkyController] should look like this:
Now we will implement [Blinky]. Due to the fact that [Blinky] interacts with the GUI class a view things must to be done in the model file.
Double click [Blinky] in the outline view to navigate to [Blinky] within the model file. Add the following code: (type it or simply copy it from the tutorial project)
[usercode1] will be generated at the beginning of the file, outside the class definition. [usercode2] will be generated within the class definition. The code imports the GUI class and instantiates the window class. Attributes for the carLights and pedLights will be declared to easily access the lights in the state machine. The Operation [destroyUser()] is a predefined operation that will be called during shutdown of the application. Within this operation, cleanup of manual coded classes can be done.
Now design the FSM of [Blinky]. Remember, as the name suggested [blinking] is a state in which the LED must be switched on and off. We will realize that by an hierarchical FSM in which the [blinking] state has two sub states.
Open the behavior diagram of [Blinky] by right clicking the [Blinky] actor in the outline view. Create two states named [blinking] and [off]. Right click to [blinking] and create a subgraph.
Create the following state machine. The trigger events between [on] and [off] are the [timeoutTick] from the [timer] port.
Create entry code for both states by right clicking the state and select [Edit State...]
Entry code of [on] is:
timer.Start(1000);
carLights.setState(TrafficLight3.YELLOW);
Entry code of [off] is:
timer.Start(1000);
carLights.setState(TrafficLight3.OFF);
Navigate to the Top level state by double clicking the [/blinking] state. Create the following state machine:
The trigger event from [off] to [blinking] is the [start] event from the [ControlPort].The trigger event from [blinking] to [off] is the [stop] event from the [ControlPort]. Note: The transition from [blinking] to [off] is a so called group transition. This is a outgoing transition from a super state (state with sub states) without specifying the concrete leave state (state without sub states). An incoming transition to a super state is called history transition.
Action code of the init transition is:
carLights = light.getCarLights();
pedLights = light.getPedLights();
carLights.setState(TrafficLight3.OFF);
pedLights.setState(TrafficLight2.OFF);
Action code from [blinking] to [off] is:
timer.Kill();
carLights.setState(TrafficLight3.OFF);
The model is complete now. You can run and debug the model as described in getting started. Have fun.
The complete model can be found in /org.eclipse.etrice.tutorials/model/Blinky.