QModMaster View Menu: Float/Int/Hex/Binary Explained The View menu in QModMaster does not change what your device sends — it changes how the same raw bytes are interpreted and displayed. Pick the wrong format and a perfectly healthy reading looks broken; pick the right one and half of all “wrong value” mysteries solve themselves. This page…
Modbus TCP vs RTU over TCP: What’s the Difference? They sound like the same thing — and that is exactly why this confuses everyone. Modbus TCP and RTU over TCP both travel over a TCP/IP network, but the bytes on the wire are different protocols. Mixing them up is one of the most common reasons…
QModMaster RTU over TCP Explained: Why There Is No Such Mode You opened QModMaster’s connection settings, looking for “RTU over TCP” — and found only two choices: Modbus RTU and Modbus TCP. It is not a missing feature or a bug. QModMaster simply has no RTU-over-TCP mode, and understanding why will save you a long…
Test Modbus with QModMaster Before Home Assistant If your Home Assistant Modbus integration shows “unavailable” sensors, stop editing YAML for a minute. Prove the physical link works first with QModMaster — a free, open-source (LGPLv3) Modbus master simulator from the upstream project. This “verify with QModMaster first” workflow is exactly what IXON’s official support documentation…
Analyze Modbus TCP with Wireshark: Capture & Troubleshooting Guide QModMaster’s Bus Monitor shows you every frame your PC sends and receives — and that is enough for most day-to-day debugging. But sometimes the problem is not in your PC at all: it is on the wire, in a switch, in a gateway, or in a…
Connect a Siemens PLC via Modbus TCP (QModMaster Test) When you configure a Siemens S7-1200 or S7-1500 as a Modbus TCP server, QModMaster is a fast way to verify the setup: connect as a Modbus TCP client, read a few holding registers, and confirm the PLC is really serving data. This guide covers the QModMaster…
Test a VFD with QModMaster via Modbus (Guide) A variable frequency drive (VFD) usually speaks Modbus RTU out of the box, which makes it one of the most common devices QModMaster users debug. This guide shows how to connect a VFD to QModMaster, read its status word, and write a frequency reference — the standard…
Modbus Function Codes Explained (01/02/03/04/05/06/15/16) Function codes are the “verbs” of Modbus: they tell the slave what to do. QModMaster supports the eight most-used ones. Here is what each does, when to use it, and where it shows up in QModMaster’s dialog. Function Codes at a Glance Code Name Description Use case 01 Read Coils…
How to Read Holding Registers (FC03): Step-by-Step Holding registers are the read/write data locations in a Modbus slave — setpoints, configuration values, measured values you need to check. Function code 03 (FC03) is how a Modbus master reads them. This guide walks you through reading holding registers in QModMaster, register by register. What QModMaster Needs…
QModMaster Bus Monitor: Reading Raw Modbus Traffic When Modbus misbehaves, opinions don’t help — bytes do. QModMaster’s bus monitor shows every byte sent and received in raw hex, timestamped. Learn to read it and you can distinguish “my request never left the PC” from “the device answered but the frame was corrupt” from “the device…
