Overview

This guide demonstrates the data acquisition process using the distributed IO M31 paired with E90/E95 SL series DTUs.

The demonstration uses the M31-XAXA0404G distributed IO and E90-DTU(400SL30). This tutorial also applies to other first-generation distributed IO models and E90 SL series radios, with differences only in IO type, IO quantity, frequency, transmission power, and configuration mode entry method. E95 SL series radios can also refer to this tutorial—they only differ in configuration methods, while all software usage and distributed IO connection procedures are identical to the E90 SL series.

Prerequisites

• E90-DTU(400SL30) × 2

• M31-XAXA0404G × 1

• 4-20mA sensor × 1

• 12V DC power supply × 3

• 433MHz antenna × 2

• USB to 485 converter × 2

• RF_Setting (E22-E9X(SL)) software (available for download from the E90-DTU(400SL22) product page on the Ebyte official website)

• Modbus Poll software (obtainable via public search engines)

• Distributed IO configuration host software

Radio Configuration

Step 1: Hardware Connection

Connect each E90-DTU(400SL30) to a USB to 485 converter, following the A-to-A and B-to-B wiring rule. Power the E90-DTU(400SL30) and plug the USB to 485 converters into your computer's USB ports.

Step 2: Enter Configuration Mode

Toggle the M0/M1 DIP switches on the side of the E90-DTU(400SL30) to configuration mode (as shown in the diagram). E90 SL series (non-isolated serial port version) radios have 4 operating modes; this tutorial only uses normal mode (transmission mode) and configuration mode. For other modes, refer to the DTU manual.

For E95 radios: Use the MODE button to switch to configuration mode. The radio is in configuration mode when the M0 indicator is off and the M1 indicator is on.

Step 3: Read Default Parameters

Open the RF_Setting (E22-E9X(SL)) software, select the corresponding serial port, enable the port, and click "Read Parameters" to retrieve the DTU's default settings.

Step 4: Configure Transmission Parameters

You may use default parameters or modify the module address and channel. For transparent transmission, both DTUs must have identical settings for module address, frequency channel, network ID, encryption key, packet length, and air data rate. In this tutorial, we only modify the module address to 1.

Step 5: Apply Settings

Click "Write" and confirm the success message on the host software. Repeat the same configuration for the second DTU, setting its module address to 1 while keeping other parameters default.

Step 6: Switch to Transmission Mode

Toggle both M0 and M1 DIP switches to the ON position.

The radio configuration is now complete.

Distributed IO Configuration

Step 1: Hardware Connection

Power on the M31-XAXA0404G. Disconnect the USB to 485 converter from one E90-DTU(400SL30) and connect it to the 485 serial port of the M31-XAXA0404G, again following the A-to-A and B-to-B wiring rule. Plug the USB end into your computer.

Step 2: Software Setup

Open the distributed IO configuration host software. Click the top-left corner and select "Serial Port" as the interface (M31 distributed IO supports both Ethernet and 485 communication for parameter configuration; this tutorial uses serial port—select Ethernet if you prefer that method). Configure the serial port number, baud rate, and other parameters, then click "Search" to detect the device.

Step 3: Parameter Configuration

Select the detected device to view its Modbus address. Click "Configure" to adjust parameters. For this tutorial, we only use the serial port and keep all other parameters at default values.

Step 4: Final Wiring

Connect the 485 port of the distributed IO to the 485 port of the E90 radio (A-to-A, B-to-B). Connect the 2-wire sensor to the AI1 channel of the distributed IO

Acquisition Test

1. Open Modbus Poll software. Click "Connection" → "Serial Port", select the serial port corresponding to the E90 radio, and set the baud rate to 9600, 8N1.

2.Click "Setup" → "Read/Write Definition". Set the Slave ID to 1 (matching the Modbus address of the distributed IO), select function code 04 (PLC area 3 address), set the register address to 0, and set the number of registers to read to 1 (to read only AI1). Click "OK".

To read AI2: Set register address to 1, number of registers to 1.
To read both AI1 and AI2: Set register address to 0, number of registers to 2.

3.You will now see the AI1 data collected by the distributed IO displayed in Modbus Poll.

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