Real-Time Embedded Systems

An embedded system refers to a software system which is integrated into a larger project, often alongside other mechanical or electrical systems. The microcontroller which controls your coffee machine is an example of a embedded system.

A real-time system is a software system that has real-time constraints; the system must make certain guarantees regarding how quickly it responds to input. An electric braking system is an example of a real-time system.

The Heron Mk II is a real-time embedded system: the software onboard must integrate and interact with solar cells, external memory, fluid actuation mechanisms, radio antenna, all within certain (small) time frames.

This introduces unique challenges. If something goes wrong, there is no one to reset the system, and once the satellite is launched, there is no way to re-program its various components; therefore the system must be robust and handle errors gracefully. On board memory (RAM) and non-volatile memory (flash storage) are limited. Communicating with the satellite requires a radio link, which is only possible when the satellite is above the ground station.