Open source implementation of ECSS CAN bus protocol for CubeSats

Abstract

With the ever growing capabilities of space-grade FPGAs and microcontrollers, spacecraft systems are evolving from centralized architectures with a single main processing unit to decentralized layouts composed of multiple intelligent nodes. The backbone of this development is the command and control bus that interconnects these units. Used in terrestrial applications since decades, the CAN bus provides performance and robustness similar to other more traditional spacecraft buses such as MIL-STD-1553, but at very low cost. The European Cooperation for Space Standardization has published a standard in mid 2015 that specifies the requirements for a CAN bus system for space application. In this paper we present the details and results of a prototype implementation of this standard for CubeSat missions. We demonstrate that the minimal implementation of this protocol stack can well be adapted to the tight constraints of microcontrollers. The main advantages of this standardized CAN bus are increased reliability and higher data throughput, as compared to other commonly employed bus systems on CubeSats.