Modbus RTU

Modbus RTU is a version of the Modbus protocol that is based on serial communication. Unlike the Modbus TCP protocol, Modbus RTU is typically used to connect sensors, actuators, and other control devices on a factory production line. It is a fast, reliable, and flexible serial communication protocol that provides reliable data transmission and control functions.

The Modbus RTU protocol uses binary encoding and can transmit data over RS-232, RS-485, or other serial communication media. Neuron Modbus RTU plugin adds an implementation based on Ethernet TCP and enables remote device data acquisition and control through a DTU device.

Add Device

Go to Configuration -> South Devices, then click Add Device to add the driver. Configure the following settings in the popup dialog box.

• Name: The name of this device node.
• Plugin: Select the Modbus RTU plugin.

Device Configuration

After clicking Create, you will be redirected to the Device Configuration page, where we will set up the parameters required for Neuron to establish a connection with the device. You can also click the device configuration icon on the southbound device card to enter the Device Configuration interface.

Configure Data Groups and Tags

After the plugin is added and configured, the next step is to establish communication between your device and Neuron by adding groups and tags to the Southbound driver.

Once device configuration is completed, navigate to the South Devices page. Click on the device card or device row to access the Group List page. Here, you can create a new group by clicking on Create, then specifying the group name and data collection interval.

Upon successfully creating a group, click on its name to proceed to the Tag List page. This page allows you to add device tags for data collection. You’ll need to provide information such as the tag address, attributes, and data type.

For information on general configuration items, see Connect to Southbound Devices. The subsequent section will concentrate on configurations specific to the driver.

Data Types

• INT16
• UINT16
• INT32
• UINT32
• INT64
• UINT64
• FLOAT
• DOUBLE
• BIT
• STRING

Address Format

SLAVE!ADDRESS[.BIT][#ENDIAN][.LEN[H][L][D][E]][.BYTES]

SLAVE

Required, Slave is the slave address or site number.

ADDRESS

Required, Address is the register address. The Modbus protocol has four areas, each area has a maximum of 65536 registers, and the address range of each area is shown in the table below. It should be noted that a storage area as large as 65536 is generally not required in practical applications. Generally, PLC manufacturers generally use an address range within 10000. Please pay attention to fill in the correct point address according to the area and function code of the device.

.BIT

Optional, specify a specific bit in a register.

#ENDIAN

Optional, byte order, applicable to data types int16/uint16/int32/uint32/float, see the table below for details.

TIP

The byte order of a tag has a higher priority than the byte order configuration of a node. That is to say, once the byte order is configured for a tag, it follows the configuration of that tag and ignores the node configuration. The byte order can be illustrated using the notation ABCD, which corresponds directly to the sequence 1234. As an example, the ABCD designation represents the standard or default Endianness 1234. (#LL).

.LEN[H][L][D][E]

When the data type is STRING, .LEN is a required field, indicating the number of bytes the string occupies. Each register contains four storage methods: H, L, D, and E, as shown in the table below.

.BYTES

Optional, read and write the length of bytes type data, applicable to bytes data type.

TIP

A register of the Modbus driver contains 2 bytes. When reading and writing Modbus register data in the bytes data type, please ensure that the bytes parameter is set to an even number.

Example Addresses

Use Case

This chapter also provides practical examples to facilitate a quick start.

• Modbus Slave Simulator
• USR DTU

Data Monitoring

After completing the point configuration, you can click Monitoring -> Data Monitoring to view device information and control devices. For details, refer to Data Monitoring.