Mostly I use M-Bus (Meter-Bus) for interfacing with metering devices but some of the meters I have acquired use Modbus rather than Meter-Bus as the interfacing protocol.<\/p>\n\n\n\n
The term “Modbus” refers to a range of interfacing standards and protocols, which can lead to some confusion – in addition to the similarity of the term Modbus to M-Bus.<\/p>\n\n\n\n
Modbus is a client-server application-layer<\/em> protocol and can run on top of different physical network technologies. Very often this is RS-485 but it could also be RS-232 or RS-422 and some devices use TCP\/IP to encapsulate Modbus data frames, with Ethernet as the transport layer for TCP\/IP.<\/p>\n\n\n\n When using Modbus over a serial line, there are two alternative ways of encoding the data:<\/p>\n\n\n\n Generally speaking, the term “Modbus” is used as shorthand for Modbus RTU over RS-485.<\/p>\n\n\n\n Reading data from a device like an electricity meter which uses Modbus RTU over RS-485 requires:<\/p>\n\n\n\n In normal (half-duplex) RS-485 there are two wires which carry the signal. Often these are labelled ‘A’ and ‘B’ but sometimes different notation is used:<\/p>\n\n\n\n For handling the Modbus protocol within Python code, the PyModbus<\/a> library is typically the best option.<\/p>\n","protected":false},"excerpt":{"rendered":" Introduction Mostly I use M-Bus (Meter-Bus) for interfacing with metering devices but some of the meters I have acquired use Modbus rather than Meter-Bus as the interfacing protocol. The term “Modbus” refers to a range of interfacing standards and protocols, … Continue reading \n
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RS-485 Cabling<\/h2>\n\n\n\n
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Modbus Software<\/h2>\n\n\n\n