Development of a web-based monitoring device for the wired Metering Bus (M-Bus) as defined in EN13757-3

The Metering Bus, also known as M Bus, is a European standard EN13757-3 to read out metering devices, like electricity, water, gas or heat meters. Although real-life M Bus networks can reach a significant size and complexity, there are only very simple protocol analyzers available. Therefore developers and installers do not have an easy and low cost possibility to analyze real bus signals. This led to the design and implementation of a web-based monitoring tool for the M Bus together with a physical bus interface to measure and records the bus signals. Therefore, in the first place a circuit was designed, which transforms the voltage and current modulated M-Bus signals to a voltage signal, which can be read out by a standard Analog-Digital-Converter (ADC). Once captured, the bus signals are displayed using a web server, which furthermore analyzes and classifies the frame fragments. As an additional feature an oscilloscope functionality is included into the tool. This makes the analyzer a powerful tool with high compatibility and flexibility. This contribution concentrates on the development of an interface circuit to read the Wired M-Bus and how the data can be regained. This article describes the general concepts from the design of the M-Bus sniffer as well as some details about the implementation and the underlying signal processing. The implementation is divided into two major parts: The implementation of the Sniffer-Driver both in hardware and software and the adaption of this driver to an existing head unit including the user interface.