TRB142 Modbus

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Main Page > TRB Gateways > TRB142 > TRB142 Manual > TRB142 WebUI > TRB142 Services section > TRB142 Modbus

The information in this page is updated in accordance with firmware version TRB14X_R_00.02.03.1

Summary[edit | edit source]

Modbus is a serial communications protocol. Simple and robust, it has become a de facto standard communication protocol and is now a commonly available means of connecting industrial electronic devices.

This manual page provides an overview of the Modbus functionality in TRB142 devices.

If you're having trouble finding this page or some of the parameters described here on your device's WebUI, you should turn on "Advanced WebUI" mode. You can do that by clicking the "Basic" button under "Mode", which is located at the top-right corner of the WebUI.

Networking trb14x manual webui basic advanced mode v1.gif

Modbus TCP slave[edit | edit source]

A Modbus TCP slave listens for connections from a master (client) and sends out a response or sets some system related parameter in accordance with the given query. This provides the user with the possibility to set or get system parameters.

The figure below is an example of the Modbus TCP window section and the table below provides information on the fields contained in that window:

Networking rutos manual modbus modbus tcp slave v1.png

Field Value Description
Enable yes | no; default: none Turns Modbus TCP on or off.
Port integer [0..65535]; default: 502 TCP port used for Modbus communications.
Device ID integer [0..255]; default: 1 The device's Modbus slave ID. When set to 0, it will respond to requests addressed to any ID.
Allow Remote Access yes | no; default: no Allows remote Modbus connections by adding an exception to the device's firewall on the port specified in the field above.
Enable custom register block yes | no; default: no Allow custom register block.

Modbus TCP Master[edit | edit source]

A Modbus master device can request data from Modbus slaves. The Modbus TCP Master section is used to configure Modbus TCP slaves.

Networking rutos manual modbus modbus tcp master v1.png

To add a new slave, simply click the 'Add' button.

You can create a maximum of 10 slave configurations.

Slave device configuration[edit | edit source]


The figure below is an example of the Slave device configuration and the table below provides information on the fields contained in that section:

Networking rutos manual modbus modbus tcp master slave configuration v1.png

Field Value Description
Enabled off | on; default: off Turns communication with the slave device on or off.
Name string; default: none Slave device's name, used for easier management purposes.
Slave ID integer [0..255]; default: none Slave ID. Each slave in a network is assigned a unique identifier ranging from 1 to 255. When the master requests data from a slave, the first byte it sends is the Slave ID. When set to 0, the slave will respond to requests addressed to any ID.
IP address ip; default: none Slave device's IP address.
Port integer [0..65535]; default: none Slave device's Modbus TCP port.
Period integer [1..86400]; default: 60 Interval at which requests are sent to the slave device.
Timeout integer [1..30]; default: 5 Maximum response wait time.

Requests configuration[edit | edit source]


A Modbus request is a way of obtaining data from Modbus slaves. The master sends a request to a slave specifying the function code to be performed. The slave then sends the requested data back to the Modbus master. You can create a maximum of 64 request configurations for each slave device.

The figure below is an example of the Requests configuration section and the table below provides information contained in the fields of that section:

Networking rutos manual modbus modbus tcp master requests configuration v1.png

Field Value Description
Name string; default: Unnamed Request name. Used for easier management purposes.
Data type 8bit INT | 8bit UINT | 16bit INT, high byte first | 16bit INT, low byte first | 16bit UINT, high byte first | 16bit UINT, low byte first | 32bit float, Byte order 1,2,3,4 | 32bit float, Byte order 4,3,2,1 | 32bit float, Byte order 2,1,4,3 | 32bit float, Byte order 3,4,1,2; default: 16bit INT, high byte first How read data will be stored.
Function Read coils (1) | Read input coils (2) | Read holding registers (3) | Read input registers (4) | Set single coil (5) | Set single coil register (6) | Set multiple coils (15) | Set multiple holding registers (16); default: Read holding registers (3) Specifies the type of register being addressed by a Modbus request.
First Register integer [0..65535]; default: 1 First Modbus register from which data will be read.
Register Count / Values integer [1..2000]; default: 1 Number of Modbus registers that will be read during the request.
Enabled off | on; default: off Turns the request on or off.
Delete [ X ] - (interactive button) Deletes the request.

After having configured a request, you should see a new 'Testing' section appear. It is used to check whether the configuration works correctly. Simply press the 'Test' button and a response should appear in the box below.

Networking rutos manual modbus modbus tcp master requests configuration testing v1.png

Alarms Configuration[edit | edit source]


Alarms are a way of setting up automated actions when some Modbus values meet user specified conditions. The figure below is an example of the Alarms Configuration list.

Networking rutos manual modbus modbus tcp master alarms configuration v1.png

It is empty by default. So, to begin editing click the 'Add' button and you should be redirected to a page such as this:

Networking rutos manual modbus modbus tcp master alarms configuration alarm configuration v1.png

Field Value Description
Enabled off | on; default: off Turns the alarm on or off.
Function code Read Coil Status (1) | Read Input Status (2) | Read Holding Registers (3) | Read Input Registers (4); default: Read Coil Status (1) Modbus function used for this alarm's Modbus request.
Register integer [1..65536]; default: none Number of the Modbus coil/input/holding-register/input-register to read from.
Condition More than | Less than | Equal to | Not Equal to; default: Equal to When a value is obtained it will be compared against the value specified in the following field. The comparison will be made in accordance with the condition specified in this field.
Value various; default: none The value against which the read data will be compared.
Value integer [0..65535]; default: none The value against which the read data will be compared.
Action frequency Every trigger | First trigger; default: Every trigger Describes how frequently the specified action will be taken.
Redundancy protection off | on; default: off Protection against executing a configured action too often.
Redundancy protection period integer [1..86400]; default: none Duration to activate redundancy protection for, measured in seconds. This field becomes visible only when 'Redundancy protection' is turned on.
Action SMS | MODBUS Write Request; default: MODBUS Write Request Action that will be taken if the condition is met. Possible actions:
  • SMS - sends and SMS message to a specified recipient(s).
  • Modbus Request - sends a Modbus Write request to a specified slave.
SMS: Message string; default: none SMS message text.
SMS: Phone number phone number; default: none Recipient's phone number.
MODBUS Write Request: IP address ip | host; default: none Modbus slave's IP address.
MODBUS Write Request: Port integer [0..65535]; default: none Modbus slave's port.
MODBUS Write Request: Timeout integer [1..30]; default: 5 Maximum time to wait for a response.
MODBUS Write Request: ID integer [1..255]; default: none Modbus slave ID.
MODBUS Write Request: Modbus function Read Force Single Coil (5) | Preset Single Register (6) | Force Multiple Coils (15) | Force Multiple Registers (16); default: Force Single Coil (5) A function code specifies the type of register being addressed by a Modbus request.
MODBUS Write Request: First register integer [0..65535]; default: none Begins reading from the register specified in this field.
MODBUS Write Request: Values integer [0..65535]; default: none Register/Coil values to be written (multiple values must be separated by space character).

MQTT Gateway

The MQTT Gateway function is used to transfer Modbus data over MQTT. Refer to the table for information on MQTT gateway configuration fields.

Networking rutos manual modbus mqtt gateway v1.png

Field Value Description
Enable off | on; default: off Turns MQTT gateway on or off.
Host ip | host; default: 127.0.0.1 IP address or hostname of an MQTT broker.
Port integer [0..65535]; default: 1883 Port number of the MQTT broker.
Request topic alphanumeric string; default: request .
Response topic alphanumeric string; default: response .
Username string; default: none Username for authentication to the MQTT broker.
Password string; default: none Password for authentication to the MQTT broker.

See also[edit | edit source]