QModMaster vs CAS Modbus Scanner: Free Options Compared
Both of these tools cost nothing: CAS Modbus Scanner is a free utility from Chipkin Automation Systems — “100% free to use, no registration required” per the vendor — and QModMaster is free, open source software (LGPLv3). The real differences are in what each one can do.
Feature Comparison
| Feature | QModMaster | CAS Modbus Scanner |
|---|---|---|
| License & Price | LGPLv3 — free, including commercial use | “100% free to use, no registration required” (per vendor) |
| Platforms | Windows 7/10/11, Linux | Windows |
| Protocols | Modbus RTU + TCP | RS232, RS485 and TCP (per vendor) |
| Reading | Function codes 01, 02, 03, 04 | Coils, inputs, holding and input registers (per vendor) |
| Writing | Function codes 05, 06, 15, 16 — full write support | Read-focused scanner (per vendor docs) |
| Bus Monitor | Built-in raw-hex bus monitor | Message log captures each message and response (per vendor) |
| Device Discovery | No — you enter the slave ID manually | Yes — discovers Modbus devices on your network (per vendor) |
| Portable | Yes — portable .zip, no installer | Installer-based (per vendor guide) |
| Support | Community only — no official tech support | From an established automation vendor |
Where QModMaster Wins
- Full write support (05, 06, 15, 16) — CAS Modbus Scanner is built for reading and discovery.
- Raw-hex bus monitor for protocol-level debugging, plus a portable no-install build.
- Linux support alongside Windows.
Where CAS Modbus Scanner Shines
- Automatic device discovery: it probes the network and finds Modbus devices when you don’t know their addresses — QModMaster can’t do that.
- Multiple connections at once, with a message log for reviewing site work back at the office (per vendor).
- Genuinely free with no registration, from a vendor that has tested it against hundreds of third-party Modbus devices (per vendor).
Frequently Asked Questions
Is CAS Modbus Scanner really free?
Yes — the vendor states it is “100% free to use, no registration required.” Like QModMaster, it costs nothing; unlike QModMaster, it is freeware rather than open source.
Can CAS Modbus Scanner write to registers?
It is designed as a read and discovery utility: it retrieves coils, inputs, holding registers, and input registers. For write testing (function codes 05, 06, 15, 16), use QModMaster.
Does CAS Modbus Scanner run on Linux?
It is a Windows utility. QModMaster runs on both Windows and Linux.
Which is better for troubleshooting a new installation?
If you don’t know the device addresses, CAS Modbus Scanner’s automatic network discovery is genuinely useful. If you need to write registers or inspect raw protocol bytes, QModMaster’s bus monitor is the stronger tool.