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viam-soleng / viam-modbus

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Viam Modbus Client Module

This repository contains the board(r/w) and sensor(r) package, these modules abstract away a modbus server as a board component, and can query the state of that server and return sensor readings.

Available via the Viam Registry!

Description

The Viam Modbus module enables seamless communication between devices by acting as a client that queries data from a Modbus server, facilitating real-time monitoring and control over connected industrial equipment. It allows for reading and writing of coils or registers on the server, enabling efficient data exchange and operational command execution. This module is essential for integrating diverse devices, ensuring interoperability and enhancing automation in industrial environments.

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Features

Modbus Client Configuration

[!NOTE]
Serial/RTU client not yet published to registry!

The Viam modbus client module supports connections over tcp and serial. Which mode is used, depends on the modbus.url prefix as explained below. As with any other Viam module you can apply the configuration to your component into the Configure section. There are two configuration areas. The modbusconfig path applies to both, the sensor and the board component.

TCP Client Example

  "modbus": {
    "url": "tcp://192.168.1.124:502",
    "word_order": "low",
    "endianness": "big",
    "timeout_ms": 10000
  }

TCP Client Configuration Attributes

Name Type Inclusion Description
url string Required TCP Config: "tcp://<ip address>:port"
timeout_ms string Optional Connection timeout
endianness string Optional
word_order string Optional
tls_client_cert string Optional Not implemented yet
tls_root_cas string Optional Not implemented yet

Serial / RTU Client Example

Add this to your modbus board or sensor component to configure the modbus client to use serial communication.

  "modbus": {
    "url": "rtu:///dev/tty...",
    "speed": 115200,
    "timeout_ms": 10000
  }

Serial Client Configuration Attributes

Name Type Inclusion Description
url string Required Serial Config: "rtu://<serial device path>"
speed string Required Bit (bit/s)
data_bits uint Optional
parity uint Optional
stop_bits uint Optional
timeout_ms string Optional Connection timeout
endianness string Optional
word_order string Optional

Modbus Sensor Configuration

The modbus sensor component allows you to read and reord modbus register values.

Sensor Component Configuration Example

{
  "blocks": [
    {
      "length": 1,
      "name": "potentiometer",
      "offset": 0,
      "type": "input_registers"
    },
    {...}
  ],
  "modbus": {...}
}

Sensor Component Block Attributes

Name Type Inclusion Description
name string Required Name of the key for the value being read
type string Required "input_registers" | "discrete_inputs" | "coils" | "holding_registers"
offset int Required Register address decimal
length int Required Number of words to include from register address

Modbus Data Model / Register Types

Register Type Access Size Features
Coil (discrete output) Read-write 1 bit Read/Write on/off value
Discrete input Read-only 1 bit Read on/off value
Input register Read-only 16 bits (0–65,535) Read measurements and statuses
Holding register Read-write 16 bits (0–65,535) Read/Write configuration values

Modbus on Wikipedia

Modbus Board Configuration

Sample Configuration Attributes for a Board Component:

{
  "gpio_pins": [
    {
      "pin_type": "input",
      "name": "DI_01",
      "offset": 4
    },
    {...}
  ],
  "analog_pins": [
    {
      "pin_type": "input",
      "data_type": "uint16",
      "name": "AI_01",
      "offset": 0
    },
    {...}
  ],
  "modbus": {...},
}

Board Component Block Attributes

Path Name Type Inclusion Description
gpio_pins|analog_pins name string Required Name of the pin
gpio_pins|analog_pins pin_type string Required "input" | "output"
gpio_pins|analog_pins offset int Required Register address decimal
analog_pins data_type string Required "uint8" | "uint16" | "uint32" | "uint64" | "float32" | "float64"

TODO:

Credits