RUT955 Modbus

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Main Page > EOL Products > RUT955 > RUT955 Manual > RUT955 WebUI > RUT955 Services section > RUT955 Modbus

The information in this page is updated in accordance with firmware version RUT9XX_R_00.06.09.5.

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 of the user manual provides an overview of the Modbus page for RUT955 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:

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.
Keep persistent connection yes | no; default: no If enabled, the connection will not be closed after each completed Modbus request.
Connection timeout integer [1..60]; default: 0 Timeout in seconds after which the connection will be closed. Use 0 to use default value provided by Operating System.
Enable custom register block yes | no; default: no Allow custom register block

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:

required value register address register number number of registers representation
System uptime 1 2 2 32 bit unsigned integer
Mobile signal strength (RSSI in dBm) 3 4 2 32 bit integer
System temperature (in 0.1 °C) 5 6 2 32 bit integer
System hostname 7 8 16 Text
GSM operator name 23 24 16 Text
Router serial number 39 40 16 Text
LAN MAC address 55 56 16 Text
Router name 71 72 16 Text
Currently active SIM card slot 87 88 16 Text
Network registration info 103 104 16 Text
Network type 119 120 16 Text
Digital input (DIN1) state 135 136 2 32 bit integer
Digital galvanically isolated input (DIN2) state 137 138 2 32 bit integer
Current WAN IP address 139 140 2 32 bit unsigned integer
Analog input value 141 142 2 32 bit integer
GPS latitude coordinate 143 144 2 32 bit float
GPS longitude coordinate 145 146 2 32 bit float
GPS fix time 147 148 16 Text (Unix timestamp×1000)
GPS date and time 163 164 16 Text (DDMMYYhhmmss)
GPS speed 179 180 2 32 bit integer
GPS satellite count 181 182 2 32 bit integer
GPS accuracy 183 184 2 32 bit float
Mobile data received today (SIM1) 185 186 2 32 bit unsigned integer
Mobile data sent today (SIM1) 187 188 2 32 bit unsigned integer
Mobile data received this week (SIM1) 189 190 2 32 bit unsigned integer
Mobile data sent this week (SIM1) 191 192 2 32 bit unsigned integer
Mobile data received this month (SIM1) 193 194 2 32 bit unsigned integer
Mobile data sent this month (SIM1) 195 196 2 32 bit unsigned integer
Mobile data received last 24h (SIM1) 197 198 2 32 bit unsigned integer
Mobile data sent last 24h (SIM1) 199 200 2 32 bit unsigned integer
Galvanically isolated open collector output status 201 202 1 16 bit unsigned integer
Relay output status 202 203 1 16 bit unsigned integer
Active SIM card 205 206 1 16 bit unsigned integer
Mobile data received last week (SIM1) 292 293 2 32 bit unsigned integer
Mobile data sent last week (SIM1) 294 295 2 32 bit unsigned integer
Mobile data received last month (SIM1) 296 297 2 32 bit unsigned integer
Mobile data sent last month (SIM1) 298 299 2 32 bit unsigned integer
Mobile data received today (SIM2) 300 301 2 32 bit unsigned integer
Mobile data sent today (SIM2) 302 303 2 32 bit unsigned integer
Mobile data received this week (SIM2) 304 305 2 32 bit unsigned integer
Mobile data sent this week (SIM2) 306 307 2 32 bit unsigned integer
Mobile data received this month (SIM2) 308 309 2 32 bit unsigned integer
Mobile data sent this month (SIM2) 310 311 2 32 bit unsigned integer
Mobile data received last 24h (SIM2) 312 313 2 32 bit unsigned integer
Mobile data sent last 24h (SIM2) 314 315 2 32 bit unsigned integer
Mobile data received last week (SIM2) 316 317 2 32 bit unsigned integer
Mobile data sent last week (SIM2) 318 319 2 32 bit unsigned integer
Mobile data received last month(SIM2) 320 321 2 32 bit unsigned integer
Mobile data sent last month (SIM2) 322 323 2 32 bit unsigned integer
Digital non-isolated input (4 PIN connector) 324 325 1 16 bit unsigned integer
Digital open collector output (4 PIN connector) 325 326 1 16 bit unsigned integer
IMSI 348 349 16 Text

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:

value to set register address register number register value description
Hostname 7 8 Hostname Changes hostname
Device name 71 72 Device name Changes device name
Digital output 1 (DOUT1) (ON/OFF*) 201 202 1 | 0 Changes the state of the open collector (OC) output
Digital output 2 (DOUT2) (ON/OFF*) 202 203 1 | 0 Changes the state of the relay output
Switch WiFi (ON/OFF*) 203 204 1 | 0 Turns WiFi ON or OFF
Switch mobile data connection (ON/OFF*) 204 205 1 | 0 Turns mobile data connection ON or OFF
Switch SIM card 205 206 1 | 2 | 0 Changes the active SIM card slot
  • 1 - switch to SIM1
  • 2 - switch to SIM2
  • 0 - switch from the the SIM card opposite of the one currently in use (SIM1 → SIM2 or SIM2 → SIM1
Reboot 206 207 1 Reboots the router
Change APN 207 208 APN code Changes APN.
The number of input registers may vary depending on the length of the APN, but the very first byte of the set APN command denotes the number of the SIM card for which to set the APN. This byte should be set to:
  • 1 - to set APN for SIM1
  • 2 - to set APN for SIM2
Switch PIN4 state (ON/OFF*) 325 326 1 | 0 Turns PIN4 state ON or OFF

* 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:

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: 60 Interval at which requests are sent to the slave device.
Timeout integer [1..30]; default: 5 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:

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 - RUT9XX 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:

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: OutputOpen 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 Serial Master

The Modbus Serial Master page is used to configure the router as a Modbus RTU master. Modbus RTU (remote terminal unit) is a serial communication protocol mainly used in communication via RS232 or RS485 serial interfaces.

RS232

This section is used to configure the Modbus RTU master's RS232 serial interface settings. Refer to the figure and table below for information on RS232 configuration.

Field Value Description
Enabled yes | no; default: no Turns Modbus RTU via RS232 on or off.
Baud rate 300 | 1200 | 2400 | 4800 | 9600 | 19200 | 38400 | 57600 | 115200; default: 115200 Serial data transmission rate (in bits per second).
Data bits 5 | 6 | 7 | 8; default: 8 Number of data bits for each character.
Parity None | Even | Odd; default: Even In serial transmission, parity is a method of detecting errors. An extra data bit is sent with each data character, arranged so that the number of 1 bits in each character, including the parity bit, is always odd or always even. If a byte is received with the wrong number of 1s, then it must have been corrupted. However, an even number of errors can pass the parity check.
  • None (N) - no parity method is used.
  • Odd (O) - the parity bit is set so that the number of "logical ones (1s)" has to be odd.
  • Even (E) - the parity bit is set so that the number of "logical ones (1s)" has to be even.
Stop bits 1 | 2; default: 1 Stop bits sent at the end of every character allow the receiving signal hardware to detect the end of a character and to resynchronise with the character stream. Electronic devices usually use one stop bit. Two stop bits are required if slow electromechanical devices are used.
Flow control None | RTS/CTS | Xon/Xoff; default: None In many circumstances a transmitter might be able to send data faster than the receiver is able to process it. To cope with this, serial lines often incorporate a "handshaking" method, usually distinguished between hardware and software handshaking.
  • RTS/CTS - hardware handshaking. RTS and CTS are turned OFF and ON from alternate ends to control data flow, for instance when a buffer is almost full.
  • Xon/Xoff - software handshaking. The Xon and Xoff characters are sent by the receiver to the sender to control when the sender will send data, i.e., these characters go in the opposite direction to the data being sent. The circuit starts in the "sending allowed" state. When the receiver's buffers approach capacity, the receiver sends the Xoff character to tell the sender to stop sending data. Later, after the receiver has emptied its buffers, it sends an Xon character to tell the sender to resume transmission.

RS485

This section is used to configure the Modbus RTU master's RS485 serial interface settings. Refer to the figure and table below for information on RS485 configuration.

Field Value Description
Enabled yes | no; default: no Turns Modbus RTU via RS485 on or off.
Baud rate 300 | 1200 | 2400 | 4800 | 9600 | 19200 | 38400 | 57600 | 115200; default: 115200 Serial data transmission rate (in bits per second).
Data bits 5 | 6 | 7 | 8; default: 8 Number of data bits for each character.
Parity None | Even | Odd; default: Even In serial transmission, parity is a method of detecting errors. An extra data bit is sent with each data character, arranged so that the number of 1 bits in each character, including the parity bit, is always odd or always even. If a byte is received with the wrong number of 1s, then it must have been corrupted. However, an even number of errors can pass the parity check.
  • None (N) - no parity method is used.
  • Odd (O) - the parity bit is set so that the number of "logical ones (1s)" has to be odd.
  • Even (E) - the parity bit is set so that the number of "logical ones (1s)" has to be even.
Stop bits 1 | 2; default: 1 Stop bits sent at the end of every character allow the receiving signal hardware to detect the end of a character and to resynchronise with the character stream. Electronic devices usually use one stop bit. Two stop bits are required if slow electromechanical devices are used.
Flow control None | RTS/CTS | Xon/Xoff; default: None In many circumstances a transmitter might be able to send data faster than the receiver is able to process it. To cope with this, serial lines often incorporate a "handshaking" method, usually distinguished between hardware and software handshaking.
  • RTS/CTS - hardware handshaking. RTS and CTS are turned OFF and ON from alternate ends to control data flow, for instance when a buffer is almost full.
  • Xon/Xoff - software handshaking. The Xon and Xoff characters are sent by the receiver to the sender to control when the sender will send data, i.e., these characters go in the opposite direction to the data being sent. The circuit starts in the "sending allowed" state. When the receiver's buffers approach capacity, the receiver sends the Xoff character to tell the sender to stop sending data. Later, after the receiver has emptied its buffers, it sends an Xon character to tell the sender to resume transmission.

Slaves

The Slaves section is used to configure new Modbus slave devices. A Modbus slave is an entity that can be called upon by a Modbus master in order to obtain some type of information from it.

To create a new Modbus slave, enter a custom name for it and click the 'Add' button. Then click the 'Edit' button next to the slave in order to enter its configuration window.

Slave settings

The Settings section is used to configure the main parameters of the Modbus slave. Refer to the figure and table below for additional information.

Field Value Description
Enabled yes | no; default: no Turns the slave on or off.
Slave ID integer [1..255]; default: 1 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.
Frequency settings period Period | Schedule; default: Period Specifies whether request frequency should happen every x amount of seconds (Period) or on a set schedule (Schedule).
Period/Schedule integer [1..9999]/; default: 10 Interval (in minutes) at which requests are sent to the slave device. Or Shedule (crontab-like, three fields (HH MM SS); e.g.. 0,12 * *).

Slave requests

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.

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

Field Value Description
Enabled yes | no; default: no Turns the request on or off.
Function Read Coil | Read Discrete Input | Read Holding Registers | Read Input Registers; default: Read Holding Registers Modbus function used in Modbus request.
First Register integer [1..65536]; default: 1 First Modbus register from which data will be read.
Number of Registers integer [1..2000]; default: none Number of Modbus registers that will be read during the request/

Slave alarms

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:

Field Value Description
Enabled yes | no; default: no Turns the alarm on or off.
Function Read Coil | Read Discrete Input | Read Holding Registers | Read Input Registers; default: Read Holding Registers Modbus function used in Modbus request.
Register integer [1..65536]; default: 1 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: More than 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 integer [0..65535]; default: 0 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.

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:

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:

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 RUT955) 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.

    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 RUT955.

    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 RUT955), 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

    Retrieved from "https://wiki.teltonika-networks.com/index.php?title=RUT955_Modbus&oldid=75508"