This paper details the implementation of a supervisory controller executing within the microcontroller of an embedded system. The plant, a dual-axis solar tracking system, is developed and modelled as a discrete event system. The events generated by the plant are monitored and controlled by the supervisor executing within the system's onboard microcontroller. An optimized, light weight Evaluation Cycle minimizes the plant to supervisor synchronization delay. Several tests show that the implemented supervisor meets the design specifications.