Template:Networking rut manual modbus

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The information in this page is updated in accordance with the [[Media:_WEBUI.bin|]] firmware version.

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 chapter is an overview of the Modbus TCP functionality for {{{name}}} devices.

Modbus TCP

Modbus TCP provides users with the possibility to set or get system parameters. The Modbus daemon acts as slave device. That means it accepts connections from a master (client) and sends out a response or sets some system related parameter in accordance with the given query.

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:

File:Networking rut9xx manual modbus modbus tcp v2.png

Template:Networking rut9xx manual modbus modbus tcp table

Get Parameters

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:

{{Template: Networking_{{{name}}}_manual_modbus_modbus_tcp_get_parameters_table}}

Set Parameters

The Modbus daemon can also set some device parameters. These parameters and explanations on how to use them are described in the table below:

{{Template: Networking_{{{name}}}_manual_modbus_modbus_tcp_set_parameters_table}}

* All ON/OFF commands only accept 0 and 1 values, which represent the following:

  • 1 - ON
  • 0 - OFF

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. You can create a maximum of 10 slave configurations.

Slave device configuration

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

[[File:{{{file_slave_configuration}}}]]

Field Value Description
Enabled yes | no; default: no 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..6400]; default: none Interval at which requests are sent to the slave device.
Timeout integer [1..30]; default: none Maximum response wait time.

Requests configuration

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:

[[File:{{{file_requests}}}]]

Field Value Description
Name string; default: Unnamed Parameter Request name. Used for easier management purposes.
Data type Hex | Ascii | 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 1 | 2 | 3 | 4 | 5 | 6 | 15 | 16; default: 3 A function code specifies the type of register being addressed by a Modbus request. The codes represent these functions:
  • 1 - read Coil Status
  • 2 - read Input Status
  • 3 - read Holding Registers
  • 4 - read Input Registers
  • 5 - force Single Coil
  • 6 - preset Single Register
  • 15 - force Multiple Coils
  • 16 - force Multiple Registers
First Register integer [1..65536]; default: 1 First Modbus register number from which data will be read.
Note - {{{series}}} Modbus Master uses register numbers, which value is +1 higher than address value.
Number of Registers integer [1..2000]; default: none Number of Modbus registers that will be read during the request.
Enabled yes | no; default: no Turns the request on or off.
Test - (interactive button) Generates a Modbus request according to given parameters in order to test the request configuration. You must first save the configuration before you can use the Test button.
Delete - (interactive button) Deletes the request.
Add - (interactive button) Adds a new request configuration.

Alarm configuration

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 Alarm configuration page and the table below provides information on fields that it contains:

[[File:{{{file_alarms}}}]]

Field Value Description
Enabled yes | no; default: no 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 in Modbus request.
Register integer [0..65535]; default: none Number of the Modbus coil/input/holding register/input register that will be read.
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.
Action SMS | Trigger output | Modbus Request; default: SMS Action that will be taken if the condition is met. Possible actions:
  • SMS - sends and SMS message to a specified recipient(s).
  • Trigger output - changes the state of a specified output(s).
  • Modbus Request - sends a Modbus request to a specified slave.
SMS: Message string; default: none SMS message text.
SMS: Phone number phone number; default: none Recipient's phone number.
Trigger output: Output Open collector output | Relay output | Both; default: Open collector output Which output(s) will be triggered.
Trigger output: I/O Action Turn On | Turn Off | Invert; default: Turn On Action that will taken on the specified output.
Modbus Request: IP address ip | host; default: none Modbus slave's IP address.
Modbus Request: Port integer [0..65535]; default: none Modbus slave's port.
Modbus Request: Timeout integer [1..30]; default: 5 Maximum time to wait for a response.
Modbus Request: ID integer [1..255]; default: none Modbus slave ID.
Modbus Request: Modbus function Read Coil Status (1) | Read Input Status (2) | Read Holding Registers (3) | Read Input Registers (4) | 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 Request: First register integer [0..65535]; default: none Begins reading from the register specified in this field.
Modbus Request: Number of registers integer [0..65535]; default: none The number of registers that will be read from the first register.


Modbus Data to Server

The Modbus Data to Server function provides you with the possibility to set up senders that transfer data collected from Modbus slaves to remote servers. To add a new data sender, enter the server's address, specify the data sending period and click the "Add" button:

[[File:{{{file_add_new_sender}}}]]

Data sender configuration

When you add a new data sender, you will be redirected to its configuration window. The figure below is an example of that window and the table below provides information on the fields that it contains:

[[File:{{{file_sender_configuration}}}]]

Field Value Description
Enabled yes | no; Default: no Turns the data sender ON or OFF
Name string; Default: none Data sender's name. used for easier management purposes
Protocol HTTP(S) | MQTT; Default: HTTP(S) Data sending protocol
JSON format json string; Default: {"ID":"%i", "TS":"%t","ST":"%s","VR":"%a"} Provides the possibility to fully customize the JSON segment
Segment count 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | All; Default: 1 Max segment count in one JSON string sent to server.
URL / Host / Connection string host | ip; Default: none Address of the server to which the data will be sent.
Important note: when using HTTPS, remember to add the https:// prefix before the URL.
Period integer [1..6400]; Default: none Data sending frequency (in seconds)
HTTP(S): Data filtering All data | By slave ID | By slave IP; Default: All data Which data this sender will transfer to the server
HTTP(S): Retry on fail yes | no; Default: no Specifies whether the data sender should retry failed attempts
HTTP(S): Custom header string; Default: no Adds a custom header(s) to HTTP requests
MQTT: Port integer [0..65535]; Default: none Port used to connect to host.
MQTT: Keepalive integer [1..640]; Default: none MQTT keepalive period in seconds.
MQTT: Topic string; Default: none Write topic to which your data will be sent.
MQTT: QoS 0 | 1 | 2; Default: 0 This field defines the guarantee of delivery for specific message.
Possible values are:
  • At most once (0)
  • At least once (1)
  • Exactly once (2)
    		•
    MQTT: Use TLS yes | no; Default: no Turns TLS authentication on or off.

    MQTT Gateway

    The MQTT Gateway function is used to transfer Modbus data (send requests, receive responses) over MQTT. When it is enabled, the device (this {{{name}}}) subscribes to a REQUEST topic and publishes on a RESPONSE topic on a specified MQTT broker. It translates received MQTT message payload to a Modbus request and relays it to the specified Modbus TCP slave.

    When the MQTT Gateway receives a response from the slave, it translates it to an MQTT message and publishes it on the RESPONSE topic.

    Below is an example of the MQTT Gateway page. Refer to the table for information on MQTT Gateway configuration fields.

    File:Networking rut9 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 string; default: request MQTT topic for sending requests.
    Response topic string; default: response MQTT topic for subscribing to responses.
    Username string; default: none Username for authentication to the MQTT broker. Leave empty if you do not use client authentication.
    Password string; default: none Password for authentication to the MQTT broker. Leave empty if you do not use client authentication.

    Request messages

    Modbus request data sent in the MQTT payload should be generated in accordance with the following format: 

    0 <COOKIE> <IP_TYPE> <IP> <PORT> <TIMEOUT> <SLAVE_ID> <MODBUS_FUNCTION> <REGISTER_NUMBER> <REGISTER_COUNT/VALUE>

    Explanation:

    • 0 - must be 0, which signifies a textual format (currently the only one implemented).
    • Cookie - a 64-bit unsigned integer in range [0..264]). A cookie is used in order to distinguish which response belongs to which request, each request and the corresponding response contain a matching cookie: a 64-bit unsigned integer.
    • IP type - host IP address type. Possible values:
      • 0 - IPv4 address;
      • 1 - IPv6 address;
      • 2 - hostname that will be resolved to an IP address.
    • IP - IP address of a Modbus TCP slave. IPv6 must be presented in full form (e.g., 2001:0db8:0000:0000:0000:8a2e:0370:7334).
    • Port - port number of the Modbus TCP slave.
    • Timeout - timeoutfor Modbus TCP connection, in seconds. Range [1..999].
    • Slave ID - Modbus TCP slave ID. Range [1..255].
    • Modbus function - Only these are supported at the moment:
      • 3 - read holding registers;
      • 6 - write to a single holding register;
      • 16 - write to multiple holding registers.
    • Register number - number of the first register (in range [1..65536]) from which the registers will be read/written to.
    • Register count/value - this value depends on the Modbus function:
      • 3 - register count (in range [1..125]); must not exceed the boundary (first register number + register count <= 65537);
      • 6 - register value (in range [0..65535]);
      • 16 - register count (in range [1..123]); must not exceed the boundary (first register number + register count <= 65537); and register values separated with commas, without spaces (e.g., 1,2,3,654,21,789); there must be exactly as many values as specified (with register count); each value must be in the range of [0..65535].

    Response messages

    A special response message can take one of the following forms: 

    <COOKIE> OK                              - for functions 6 and 16
<COOKIE> OK <VALUE> <VALUE> <VALUE>...   - for function 3, where <VALUE> <VALUE> <VALUE>... are read register values
<COOKIE> ERROR: ...                      - for failures, where ... is the error description

    Examples

    Below are a few examples of controlling/monitoring the internal Modbus TCP Slave on {{{name}}}.

    Reboot the device

    • Request:
      0 65432 0 192.168.1.1 502 5 1 6 206 1
    • Response:
      65432 OK

    Retrieve uptime

    • Request:
      0 65432 0 192.168.1.1 502 5 1 3 2 2
    • Response:
      65432 OK 0 5590

    If you're using Eclipse Mosquitto (MQTT implementation used on {{{name}}}), Publish/Subscribe commands may look something like this:

    Retrieve uptime

    • Request:
      mosquitto_pub -h 192.168.1.1 -p 1883 -t request -m "0 65432 0 192.168.1.1 502 5 1 3 2 2"
    • Response:
      mosquitto_sub -h 192.168.1.1 -p 1883 -t response
65432 OK 0 5590


    See also

    Template:Networking device modbus see also

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

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