Improvement of RS-485 performance over long distances using the ToLHnet protocol

This paper presents a technique to extend the transmission range over a single RS-485 cable, without requiring installation of expensive and cumbersome RS-485 repeaters, to virtually unlimited distances, while simultaneously improving transmission speeds between closer nodes. This was accomplished by leveraging the routing capabilities embedded into each node that implements the recently released and extremely lightweight ToLHnet protocol. With it, each network node can act as a sort of “smart repeater” only when there is need to, optimizing the overall network throughput. The key ideas underlying the routing strategies are here described, together with details of a prototype node and experimental results demonstrating transmission at distances well above the traditional limit.

I. Introduction

In the modern, interconnected world, an increased utility can often be found by allowing the most disparate gadgets and devices to communicate together, in what is becoming popularly known as the Internet of Things (IoT). Nowadays a lot of research is spent in trying to make the IoT possible by using mostly wireless communications media. Still, there are cases where the intrinsic safety and reliability of a wired medium [1], its bandwidth, the need to continuously deliver power to the devices, or simply an extremely harsh electromagnetic environment [2] might make a cable preferred over a wireless link.