Dynamically Reconfigurable Coprocessor for Floating-Point Arithmetic Capability in Small Satellites

Field Programmable Gate Arrays (FPGAs) are increasing used in small satellite missions for tasks ranging from command & data handling to sensor data processing. An FPGA is a dense system of computing resources, logic gates, memory, look-up tables (LUTs), etc. The size, mass, input/output (I/O), and low power constraints of small satellites prevent designers from taking advantage of the full capability of FPGAs. Implemented yet unused components waste power and FPGA resources. This paper proposes increasing FPGA-based computer capability by implementing a dynamically reconfigurable coprocessor in parallel to the main processor on the FPGA. The coprocessor functions as a hardware accelerator for data intensive operations or operations unsupported by the main processor. This approach minimizes the coprocessor's footprint by reconfiguring the coprocessor in-real time to reuse the same FPGA resources for different stages of a computation. Complex computational operations are broken up into multiple discrete stages with individual coprocessors sequentially performing each stage. This allows the required FPGA resources for the coprocessor to be minimized while taking advantage of the computational boost in FPGA hardware instead of the main processor. A secondary benefit to is this approach is that the coprocessors can support functionality not provided by the main processor. To investigate the feasibility of this approach, a set of floating-point operation were implemented as coprocessors and integrated into a RISC-V soft processor system. The results of this proof-of-concept provide evidence that the use of dynamically reconfigurable floating-point coprocessors has the ability to increase the computational capability of small satellite computers while fitting within the constrained resources of such missions.