Template:Networking rutos manual modbus

Summary

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 {{{name}}} 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 "Advanced" button, located at the top of the WebUI.

Modbus TCP slave

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:

Field	Value	Description
Enable	off | on; 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	off | on; default: off	Allows remote Modbus connections by adding an exception to the device's firewall on the port specified in the field above.
Keep persistent connection	off | on; default: off	Allows keep the connection open after responding a Modbus TCP master request.
Connection timeout	integer; default: 0	Sets TCP timeout in seconds after which the connection is forcefully closed.
Enable custom register block	off | on; default: off	Allows the usage of custom register block.

Get Parameters

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Modbus parameters are held within registers. Each register contains 2 bytes of information. For simplification, the number of registers for storing numbers is 2 (4 bytes), while the number of registers for storing text information is 16 (32 bytes).

The register numbers and corresponding system values are described in the table below:

required value	register address	register number	number of registers	representation
System uptime	1	2	2	32 bit unsigned integer
System hostname	7	8	16	Text
Router serial number	39	40	16	Text
LAN MAC address	55	56	16	Text
Router name	71	72	16	Text
Current WAN IP address	139	140	2	8 bit unsigned integer
Digital non-isolated input	324	325	1	16 bit unsigned integer
Digital open collector output	325	326	1	16 bit unsigned integer
PIN 3 direction	326	327	1	16 bit unsigned integer
PIN 4 direction	327	328	1	16 bit unsigned integer
Unix timestamp	364	365	2	32 bit unsigned integer
Local ISO time	366	367	12	Text
UTC time	378	379	12	Text
LAN IP	394	395	2	8 bit unsigned integer

Set Parameters

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The Modbus daemon can also set some device parameters.

value to set	register address	register number	register value	description
Hostname	7	8	Hostname (in decimal form)	Changes hostname
Device name	71	72	Device name (in decimal form)	Changes device name
Reboot	206	207	1	Reboots the router
Switch PIN 3 state	324	325	1|0	Toggles PIN 3 ON or OFF, when output is selected
Switch PIN 4 state	325	326	1|0	Toggles PIN 4 ON or OFF, when output is selected
Switch PIN 3 direction	326	327	1|0	Toggles PIN 3 direction between INPUT (0) or OUTPUT (1)
Switch PIN 4 direction	327	328	1|0	Toggles PIN 4 direction between INPUT (0) or OUTPUT (1)
Change LAN IP	394	395	IPv4 (in decimal form)	Changes device LAN IP

Modbus TCP Master

A Modbus Master device can request data from Modbus slaves. The Modbus TCP Master section is used to configure Modbus TCP slaves. By default, the slave list is empty. To add a new slave, click the 'Add' button

After clicking 'Add' you will be redirected to the newly added slave's configuration page.

You can create a maximum of 10 slave configurations.

Slave Device Configuration

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The Slave Device Configuration section is used to configure the parameters or Modbus TCP slaves that the Master (this {{{name}}} device) will querying with requests. The figure below is an example of the Slave Device Configuration and the table below provides information on the fields contained in that section:

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

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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 Request Configuration list is empty by default. To add a new Request Configuration loon to the Add New Instance section. Enter a custom name into the 'Name' field and click the 'Add' button:

The new Request Configuration should become visible in the list:

Field	Value	Description
Name	string; default: Unnamed	Name of this Request Configuration. 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	Defines 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.

Additional note:By default the newly added Request Configurations are turned off. You can use the on/off slider to the right of the Request Configuration to turn it on:

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After having configured a request, you should see a new 'Request Configuration Testing' section appear. It is used to check whether the configuration works correctly. Simply click the 'Test' button and a response should appear in the box below. A successful response to a test may look something like this:

Alarms Configuration

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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.

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

File: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.

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

[[Category:{{{name}}} Services section]]