A production-ready Modbus RTU/TCP data logger with multi-threaded GUI, 8 data formats, and full byte-order support.
This is a commercial tool, sold on Gumroad. Source code is included in your purchase.
- Modbus RTU + TCP in one tool — switch with one click
- 8 data formats — INT16, UINT16, INT32, UINT32, FLOAT32, FLOAT64, hex, ASCII
- All 4 byte orders — ABCD / CDAB / BADC / DCBA, including the Schneider word-swap that breaks most pymodbus scripts (read why →)
- Multi-threaded GUI — never freezes during long polls
- Auto-CRC validation for RTU frames
- CSV export — pair with CSV Dashboard for free interactive plotting
- Single-file Python — no install hell, no cloud dependencies
Most "Modbus debuggers" cost $200-800, run only on Windows, and ship as a 50MB installer that bundles a 2010-era UI. Free alternatives are either CLI-only or break the moment a Schneider PLC sends a CDAB float.
This tool is what I wished existed when I started doing industrial integration work: small, focused, runs on Windows / Mac / Linux, and handles the byte-order quirks every real-world device throws at you.
| Device | Connection | Notes |
|---|---|---|
| Schneider M221, M241 | TCP / RTU | CDAB byte order |
| Siemens S7-1200, S7-1500 | TCP (Modbus wrapper) | CDAB or ABCD |
| Allen-Bradley CompactLogix | TCP (via Prosoft) | ABCD |
| Mitsubishi FX | RTU | ABCD |
| Delta DVP | RTU | ABCD |
| Schneider PM5xxx energy meters | TCP | CDAB |
| ABB ACS / Schneider Altivar VFDs | TCP / RTU | Mixed — test all 4 |
→ Modbus Logger Pro on Gumroad — $49
Or grab the Industrial Integration Bundle ($119) and save $48 vs buying the Modbus, MQTT, and OPC UA tools separately.
modbus_logger.py— Single-file Python applicationrequirements.txt— Pinned dependenciesREADME.md— Setup guide + troubleshooting- Commercial use license per Gumroad EULA
Commercial use license per Gumroad EULA. You may use this software at the company that purchased it for any commercial purpose. Redistribution, resale, or open-sourcing the code is not permitted.
- Reply to your Gumroad purchase email — I read every one
- Bug reports / feature requests welcome via GitHub Issues
I write about industrial Python and protocol internals at dev.to/philyeh, and post Chinese versions on iThelp.
— Phil Yeh · Senior Automation Engineer · Industrial Python · Developer Tools