Design of Micro-drone Autopilot Architecture with Static Scheduling Optimization

This paper presents the internal architecture of a Modifiable Off-the-Shelf (MOTS) open-source autopilot. The analysis of a set of functional and hardware requirements reveals that the core of the autopilot can be implemented as a single-threaded system, with a main loop acting as a non-preemptive static scheduler, provided that the internal structure is well-organized. We discuss how the type of bus used for sensor communication influences the nature of the events received from the sensors, whether they are solicited or unsolicited. We demonstrate that, depending on the workload that a main loop iteration must handle, the execution time of a single iteration can exceed the defined period, potentially causing delays in attitude correction. Finally, we explore the degrees of freedom available to mitigate the impact of such overloads by smoothing out the periodic workload.