TosNet: An easy-to-use, real-time communications protocol for modular, distributed robot controllers

This paper presents the TosNet network, created for robotics research, education, and prototyping, emphasizing ease of use, robustness, compactness, flexibility and fast hard real-time response, to allow distribution of all levels of the robot control system. The current implementation of TosNet supports up to 15 nodes, with cycle-rates up to 25 kHz, depending on the configuration. The protocol stack is completely specified as VHDL code, implemented in an FPGA. The physical layer is implemented with Toslink fiberoptic links, offering a compact, robust and highly available link technology. The network uses a shared memory model, where a block of memory is mirrored across all attached nodes each cycle, offering a simple, easy-to-use software interface between nodes.