We introduce an inexpensive, low complexity power surface system capable of simultaneously providing wireless power and bidirectional communication from a surface to multiple mobile robots. This system enables continuous operation of a swarm-sized population of battery-less robots. Our first prototype consists of a 60 cm times 60 cm power surface that provides power and bidirectional communication to an initial evaluation group of five test robots, each one consuming 200 mW. Unlike typical non-resonant inductive (transformer) coupling, power transmission in this system is achieved through magnetic flux coupling between a high Q L-C resonator placed beneath the operating surface and a non-resonant pickup coil on each robot. We explore the design of the pickup coil and conditioning circuitry, and we characterize the position-dependent power density of a static load representative of a small autonomous robot operating on the surface. We demonstrate a continuous power density averaging 4.1 mW/cm<sup>2</sup> for a static load, and develop much greater peak power for dynamic loads via capacitor storage and power conditioning circuitry. We also demonstrate simultaneous broadcast communication between the surface and all robots via amplitude modulation of the magnetic field, and communication between individual robots and the surface via load modulation.