Deploying the Application on the Toolstick
Deploying the application on the Toolstick requires only providing the board-specific initialization and the time-tick interrupt, which must call the QP-nano function QF_tick() to generate the TIMEOUT events. The PELICAN example contains a small board support package (bsp.c) for the Toolstick, which has been modeled largely after the standard PWM_demo application that comes on the Toolstick CD.
The code accompanying this article contains an extensive README file explaining all the examples included and the usual workarounds for minor bugs in the demo tools and their incompatibilities. I just wanted to mention here that I ended up using the 4-KB KickStart(tm) 8051 compiler from IAR Systems, instead of the 2-KB demo version of the Keil 8051 compiler that comes with the Toolstick. Finally, because the memory footprint is of primary interest in this article, here are the numbers I've obtained with the IAR 8051 compiler optimized for size: QP-nano: 1254 bytes of CODE, 1 byte of DATA; application totals: 2712 bytes of CODE, 16 bytes of DATA, 88 bytes of IDATA (including 64 bytes of stack), 1 byte of BIT memory.
Conclusions
UML-style state machines can help you produce efficient, maintainable, testable systems with well understood behavior, rather than creating the usual "spaghetti" code littered with convoluted ifs and elses. In this article I've demonstrated that the technique is applicable to quite small systems, starting from about 4KB of ROM, and some 128 bytes of RAM.
Contrary to widespread misconceptions, you don't need big UML tools to take full advantage of the hierarchical state nesting and the guaranteed initialization and cleanup of states, which are the most important features of UML statecharts. In fact, manual coding of a nontrivial PELICAN crossing statechart turned out to be a rather simple exercise in following just a few straightforward rules. The implementation technique based on an "event processor", such as QP-nano, results in concise, highly maintainable code that truly reflects the statechart structure without any repetitions. The resulting state machine representation in C is flexible, allowing even sweeping changes in the state machine structure to be accomplished quite easily, at any stage of the project.
Once you design a system with UML statecharts, you will not want to go back to the "spaghetti" code or even to the traditional RTOS. Welcome to the 21st century.
References
IAR Embedded Workbench for 8051: KickStart Version.
