his document reports the process of design, implementation, and testing of an On-Board Computer for CubeSats in a single 1U-sized CubeSat PCB. The aim is to design a modular, cheap, e cient and exible product than could be easily reproduced and implemented in forthcoming CubeSats missions. The document describes all the hardware design phases, from the selection of components to the creation of the circuits and blocks, following with the physical design of the layout in two stackable boards, and nally the actual integration and subsequent electrical test of the components. The project ended successfully with a prototype of the OBC allowing the boot of a Linux operative system from a µSD card, and the documentation needed to reproduce the work and manufacture new products.