I/O RS Modules - Modbus RTU - Work with the protocol

The following article describes how to prepare multiprotocol I/O modules of the MINI, MIX, and MAX series to work with the Modbus RTU protocol.

1. Preparation for work with the module

In the first step, you need to prepare a computer with iSMA Configurator installed (it can be downloaded for free from iSMA CONTROLLI Download Center a mini USB cable and a small flat screwdriver.

2. Configuration of DIP switch and rotary switch

First, correctly configure the DIP switch and rotary switch located under the top cover of the device. Rotary switches are used to set the Modbus address which must be unique for each device on the network. The address is set according to the formula:

Address = S2x10 + S1.

Picture 1. “Rotary switch”.

Using the first three dip switches, set the baud rate according to the table below. The "baud rate" must be the same for all devices on the network.

Picture 2. Instruction for setting the “Baud rate” parameter.

To start the Modbus RTU protocol in the module, set the pins 4 and 5 of the “Dip switch” to the OFF position, according to the table below:

Picture 3. Instruction for selecting a communication protocol.

3. Device configuration using iSMA Configurator

Before proceeding to this point, it is recommended to first read the iSMA Configurator manual I/O Modules - iSMA Configurator - Connecting with the module, reading and saving values.

First, connect to the device with iSMA Configurator and go to the “RS485 Configuration” tab. In this tab, set the value for the parameters: “Stop bits”, “Data bits” and “Parity bits” the same as for the entire Modbus RTU network. Using this tab, you can also verify the correctness of the "Baud rate" and "Modbus address" values, using the "Actual baud rate" and "MAC address" parameters.

Picture 4. View of the "RS485 Configuration" tab in iSMA Configurator.