smf State Machine Framework HSM PSiCC2 Example

This example implements an event-driven hierarchical state machine using the State Machine Framework (SMF). It reproduces the statechart shown in Figure 2.11 of Practical UML Statecharts in C/C++, 2nd Edition, by Miro Samek (PSiCC2). The ebook is available at https://www.state-machine.com/psicc2.

For each state, the entry, run, and exit actions are logged to the console, as well as logging when a state handles an event or explicitly ignores it and passes it up to the parent state.

It should be possible to build and run this demo on most boards or emulators that support NSH, SMF, and message queues.

Configuration

  • CONFIG_EXAMPLES_SMF – Enables the SMF PSiCC2 demo.

  • CONFIG_NSH_BUILTIN_APPS – Build the demo as an NSH built-in application.

  • CONFIG_SYSTEM_SMF – Enable the State Machine Framework support.

  • CONFIG_SYSTEM_SMF_ANCESTOR_SUPPORT – Enable ancestor/parent state support.

  • CONFIG_SYSTEM_SMF_INITIAL_TRANSITION – Enable initial transition support.

  • CONFIG_DISABLE_MQUEUE=n – Message queue support must be available.

  • CONFIG_EXAMPLES_SMF_PROGNAME – Program name, default hsm_psicc2.

  • CONFIG_EXAMPLES_SMF_PRIORITY – Priority of the SMF task, default 100.

  • CONFIG_EXAMPLES_SMF_STACKSIZE – Stack size of the SMF task, default 2048.

  • CONFIG_EXAMPLES_SMF_QUEUE_SIZE – Size of the message queue, default 10.

  • CONFIG_EXAMPLES_SMF_MQ_NAME – Name of the message queue, default /hsm_psicc2_mq.

Usage

The demo registers the hsm_psicc2 NSH command (configurable via CONFIG_EXAMPLES_SMF_PROGNAME):

hsm_psicc2 start
hsm_psicc2 event <A..I>
hsm_psicc2 terminate

  • start spawns the state machine thread and initializes the SMF context.

  • event <A..I> sends events A through I to the state machine (PSiCC2 Figure 2.11).

  • terminate stops the state machine thread; there is no way to restart it and further events are not processed.

Comparison to PSiCC2 Output

Not all transitions modeled in UML may be supported by the State Machine Framework. Unsupported transitions may lead to results different from the example run in PSiCC2 Section 2.3.15. The differences are not listed here since it is hoped SMF will support these transitions in the future and the list would become outdated.