Recommended ModulesLink Products
QModMaster works seamlessly with these industrial communication modules for Modbus RTU/TCP testing and commissioning
RS-485 Transceiver
- Up to 5000VDC isolation
- ESD protection ±8kV
- 256 nodes on bus
- -40°C to +105°C
CAN Transceiver
- Up to 5000VDC isolation
- CAN 2.0A/2.0B protocol
- ESD ±8kV, Surge ±4kV
- -40°C to +105°C
Digital Isolators
- Up to 5000VDC isolation
- CMTI >100kV/µs
- Data rate 150Mbps
- -40°C to +125°C
Version
0.5.3-beta
File Size
23.2 MB (ZIP)
Platform
Windows 10/11 64-bit
License
GPL-3.0 (Open Source)
Overview
QModMaster is a free Qt-based Modbus master application that provides a graphical user interface for testing and debugging Modbus RTU and TCP communication. It is widely used in industrial automation for commissioning, troubleshooting and validating Modbus devices.
As a portable application, QModMaster requires no installation - simply extract the ZIP archive and run the executable. This makes it ideal for field engineers who need a reliable Modbus testing tool on any Windows computer.
Key Features
⚙ Modbus RTU Support
Full Modbus RTU master over RS-232/RS-485 serial ports with configurable baud rate, parity and stop bits.
🌐 Modbus TCP Support
Modbus TCP master over Ethernet with configurable IP address and port. Connect to any TCP gateway or device.
📊 Bus Monitor
Real-time bus monitor displays all Modbus traffic on the network. Inspect request and response frames in detail.
💾 Session Save/Load
Save your communication sessions including device settings and register configurations for quick reuse.
📱 Portable
No installation required. Extract and run from any folder or USB drive. No admin privileges needed.
🛠 All Function Codes
Supports all standard Modbus function codes: read/write coils, discrete inputs, holding registers and input registers.
Quick Start Guide
Modbus RTU Testing
- Extract the downloaded ZIP file to any folder on your computer
- Connect your RS-485 USB adapter to the computer and wire it to the Modbus device
- Launch QModMaster.exe from the extracted folder
- Select Modbus RTU mode from the toolbar dropdown
- Configure serial port: Select COM port, set baud rate (typically 9600 or 19200), parity (8E1 or 8N1)
- Set slave address (1-247) and register range to read
- Click Read to send the Modbus request and view the response data
Modbus TCP Testing
- Launch QModMaster and select Modbus TCP mode
- Enter the IP address of your Modbus TCP device or gateway (default port: 502)
- Set slave ID and register address range
- Click Read to query the device over Ethernet
Typical Configuration
Common Serial Settings for Industrial Devices
| Parameter | Common Value | Notes |
|---|---|---|
| Baud Rate | 9600 / 19200 | Must match device setting |
| Data Bits | 8 | Standard for Modbus RTU |
| Parity | Even / None | 8E1 or 8N1 most common |
| Stop Bits | 1 | 1 for 8E1, 2 for 8N1 |
| Slave Address | 1-247 | Check device DIP switches or config |
| Timeout | 1000 ms | Increase for slow devices |
Compatible with ModulesLink Products
QModMaster works seamlessly with all ModulesLink Modbus communication modules including ML-MOD-RTU, ML-MOD-WIFI and ML-MOD-PROTO gateways. Use it to verify communication during commissioning and troubleshooting.