In this contribution we present practical experiences from realizing a prototype of the first truly fault-tolerant and autonomously operating avionics suite for miniaturized satellite down to the size of a 2U CubeSat. Our initial demonstrator setup consists of a mix of COTS parts and FPGA development boards, which we gradually expanded in scope and capabilities. After four iterations of PCB development and manufacturing, we have condensed this design to a fully integrated custom PCB-based prototype. Our fourth architecture iteration is stackable and is designed to fit on an 80×80mm PCB footprint. It is furthermore capable of operating as generic satellite subsystem node, functioning in a distributed, fault-tolerant, interconnected manner together with other subsystems. Each node is fully replaceable by two or more neighboring subsystem-nodes. In consequence, we achieve a satellite bus setup which is in spirit similar to integrated modular avionics and modern fault-tolerant avionics network architectures used in other fields. We realize this setup through a high-speed chip-to-chip network in a compact CubeSat form factor
