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Microcontroller-based embedded systems are vulnerable to memory safety errors and must be robust and responsive because they are often used in unmanned and mission-critical scenarios. The Rust programming language offers an appealing compile-time solution for memory safety but leaves stack overflows unresolved and foils zero-latency interrupt handling. We present Hopter, a Rust-based embedded operating system (OS) that provides memory safety, sys- tem robustness, and interrupt responsiveness to embedded systems while requiring minimal application cooperation. Hopter executes Rust code under a novel finite-stack semantics that converts stack overflows into Rust panics, enabling recovery from fatal errors through stack unwinding and restart. Hopter also employs a novel mechanism called soft-locks so that the OS never disables interrupts. We compare Hopter with other well-known embedded OSes using controlled workloads and report our experience using Hopter to develop a flight control system for a miniature drone and a gateway system for Internet of Things (IoT). We demonstrate that Hopter is well-suited for resource-constrained microcontrollers and supports error recovery for real-time workloads. 

Stack unwinding is a well-established approach for handling panics in Rust programs. However, its feasibility on resource- constrained embedded systems has been unclear due to the associated overhead and complexity. This paper presents our experience of implementing stack unwinding and panic recovery within a Rust-based soft real-time embedded oper- ating system. We describe several novel optimizations that help achieve adequate performance for a ying drone with a CPU overhead of 2.6% and a storage overhead of 26.0% to recover from panics in application tasks and interrupt handlers. 

We present POD, a smartphone that flies, as a new way to achieve hands-free, eyes-up mobile computing. Unlike existing drone-carried user interfaces, POD features a smartphone-sized display and the computing and sensing power of a modern smartphone. We share our experience in prototyping POD, discuss the technical challenges facing it, and describe early results toward addressing them.