Fig. 1

Linear routing with Dijkstra algorithm. An example of an RS-485 bus connecting ten nodes uniformly spaced with an inter-node distance ℓ is presented. The transmission speed is assumed to have been chosen so as to allow reliable reception up to a distance of at least 3ℓ. Among all the possible graph edges, represented by arcs, the Dijkstra routing algorithms selected the tree highlighted in red. If the inter-node distance is exactly uniform, it results in many different paths having exactly the same cost, so the algorithm picks one essentially at random (the algorithm itself is deterministic, but the results will depend on the details of the implementation and on hardly predictable rounding errors)