Medusa: Managing Concurrency and Communication in Embedded Systems.

Microcontroller systems are almost always concurrent, event-driven systems. They monitor external events and control actuators. Typically, these systems are written in C with very little support from system software. The concurrency in these applications is implemented with hand-coded interrupt routines. Race conditions and other classic pitfalls of implementing parallel systems in shared-state programming languages have caused catastrophic, and sometimes lethal, failures in the past. We have designed and implemented Medusa, a programming environment for microcontrollers using the actor model. This paper presents three key contributions. First, the Medusa language, which is derived from Python and Erlang. Second, an implementation that runs on systems several orders of magnitude smaller than any other actor-model system previously described. Finally, a novel bridging mechanism to extend the domain of the actor-model to hardware. Combined, these innovations make it far easier to build complex, reliable and safe embedded systems.