Understanding Modbus

The quiet workhorse of industrial communication, finally explained. Modbus is everywhere. Four decades after it was invented, it still connects the meters, drives, sensors, controllers, and SCADA systems that run modern industry, and sooner or later anyone working with industrial or embedded systems has to deal with it. Most references describe the protocol and stop there. This book teaches you how Modbus actually works, and then proves it by making it run in front of you.

Starting from a single bit and building all the way to a working monitoring-and-control application, Understanding Modbus walks through the data model, the frame byte by byte, every common function code, and all three transports: RTU and ASCII on serial lines, and TCP over Ethernet. Then it puts an inexpensive microcomputer on your desk and turns the theory into running Python: you will write clients and servers, talk to real serial devices over RS-485, decode signed and floating-point values, build a complete control project, troubleshoot faults with a clear method, secure your deployment, and see exactly where Modbus fits among PLCs, SCADA, gateways, and the newer protocols layered above it.

What you will learn: the four-table data model and the addressing that trips up every newcomer; the Modbus frame, byte by byte, across serial and Ethernet; every common function code, plus exceptions and diagnostics; hands-on clients and servers in Python with pymodbus; Modbus RTU over real RS-485 wiring, start to finish; decoding 32-bit integers and IEEE floats, and the word-order trap; a repeatable method for troubleshooting any Modbus fault; and performance, polling strategy, and security in the real world. Fully illustrated, with hands-on examples, end-of-chapter exercises, and quick-reference appendices you will return to for years.