GSI Modbus Test Lite app for iPhone and iPad

This app is a fast and simple utility for testing Modbus devices over wifi. It is a completely free app with retina support for both iPad and iPhone.

Just tap the Comm button for the communication setup page to enter the communication parameters for your device and send it a Modbus-TCP poll.

The app will send an FC3 (Read Holding Registers) command to the device ID that you specify. You can also specify the starting address (0-65535) and the number of registers (typically 1-125 depending on your device). Raw poll & reply data, including TCP headers, will be shown on the Comm page.

If you are accustomed to specifying your register addresses in "Modicon format", the starting address range of 0-65535 used in this app corresponds to an extended Modicon address range of 40001 to 465535.

When you exit the Comm page, the main tabular page will show the Modbus registers that were polled and their data in both decimal and hexadecimal format.

Your device must be on the same wifi network with the device that you want to test. Be sure to use the Settings app to configure your network settings before using the app or you will surely get socket connection errors.

This is our free, lite version of the app and it is only intended to serve as a quick & easy Modbus-TCP test utility. As such its capabilities are rather limited, so enjoy it if it suits your needs.
✒Only FC3 is supported and the connect & response timeouts are fixed.
✒All Modbus register data is treated as 16-bit unsigned integer data.
✒Continuous polling is not supported – you must tap the Send Poll button to initiate each individual poll to your device.
✒Only Modbus-TCP communication is supported: other variants such as Modbus-RTU over TCP, Modbus-ASCII over TCP, UDP, SSL, etc. are not supported in this app.

If you require more functionality, please check out our full version app.