IoT Edge PLC Publisher

This project provides Azure IoT Edge module for publishing PLC Tags values to Azure IoT Edge and Azure IoT Hub.

Usage

To use the module, you need to deploy the following Azure IoT Edge module:

 "PlcPublisher": {
        "restartPolicy": "always",
        "settings": {
            "image": "ghcr.io/iot-edge-fundation/iot-edge-plc-publisher:latest",
            "createOptions": "{}"
        },
        "status": "running",
        "type": "docker"
    }

Edge Hub routing

    "routes": {
        "PlcPublisherToUpstream": "FROM /messages/modules/PlcPublisher/* INTO $upstream",
    },

Note: The default output of the module is tag, you can also use this explicit output name in your configuration.

Module properties

This module uses desired properties to configure the tags you want to pull. Here is an example of configuration that pulls every 1 sec a tag array of 10 values from a PLC.

{
...
    "properties": {
        "desired": {
            "tags": [
                {
                    "gateway": "192.168.0.100",
                    "path": "1,0",
                    "plcType": "ControlLogix",
                    "tagType": "ARRAY_DINT",
                    "tagName": "MY_ARRAY",
                    "arrayLength": 10,
                    "pollingInterval": 1000,
                }
            ]
        }
    }
...
}

Note: Please see below mode configuration options that might fit your needs.

Supported PLCs

It can be one of the following values:

• ControlLogix: Control Logix-class PLC
• Plc5: PLC/5 PLC
• Slc500: SLC 500 PLC
• LogixPccc: Control Logix-class PLC using the PLC/5 protocol
• Micro800: Micro 800 PLC
• MicroLogix: Micro Logix PLC
• Omron: Omron PLC

Supported Tag Types

It can be one of the following values:

• BOOL: Boolean
• SINT: Signed 8-bit integer
• INT: Signed 16-bit integer
• DINT: Signed 32-bit integer
• LINT: Signed 64-bit integer
• LREAL: Signed 64-bit floating point
• REAL: Signed 32-bit floating point
• STRING: String
• ARRAY_BOOL: Array of boolean
• ARRAY_SINT: Array of signed 8-bit integer
• ARRAY_INT: Array of signed 16-bit integer
• ARRAY_DINT: Array of signed 32-bit integer
• ARRAY_LINT: Array of signed 64-bit integer
• ARRAY_LREAL: Array of signed 64-bit floating point
• ARRAY_REAL: Array of signed 32-bit floating point
• ARRAY_STRING: Array of string

Direct Methods

This module exposes the following direct methods:

• ListTags: List all the tags available in the PLC.
• ListUdtTypes: List all the UDT types available in the PLC.
• ListPrograms: List all the programs available in the PLC.
• ReadTag: Read a tag value.
• ReadArray: Read an array value.

Payloads

For the ListTags, ListUdtTypes and ListPrograms methods, the payload is a JSON object with the following structure:

{
    "gateway": "`<the gateway ip or hostname>`",
    "path": "<the path to the PLC>",
    "plcType": "<the PLC type>",
}

For ReadTag, the payload is a JSON object with the following structure:

{
    "gateway": "`<the gateway ip or hostname>`",
    "path": "<the path to the PLC>",
    "plcType": "<the PLC type>",
    "tagName": "<the tag name>",
    "tagType": "<the tag type>"
}

For ReadArray, the payload is a JSON object with the following structure:

{
    "gateway": "`<the gateway ip or hostname>`",
    "path": "<the path to the PLC>",
    "plcType": "<the PLC type>",
    "tagName": "<the tag name>",
    "tagType": "<the tag type>",
    "arrayLength": "<the array size>",
}

Module Twin

The module accepts the following properties in the module twin:

{
    "properties": {
        "desired": {
            "tags": [
                {
                  "gateway": "`<the gateway ip or hostname>`",
                  "path": "<the path to the PLC>",
                  "plcType": "<the PLC type>",
                  "tagName": "<the tag name>",
                  "tagType": "<the tag type>",
                  "pollingInterval": "<the polling interval in milliseconds>"
                  "arrayLength": "<OPTIONAL - the array size if reading an array>",
                  "transform": "<OPTIONAL - the transform to apply to the value>"
               }
            ]
        }
    }
}

Transformation

When polling values, the module can transform the value before sending it to Azure IoT Hub. The transformation is done using the JMESPath query language.

Note: the transformation uses https://github.com/WorkMaze/JUST.net.

Ex:

{
    "gateway": "<PLC_IP>",
    "path": "1,0",
    "plcType": "ControlLogix",
    "tagType": "ARRAY_DINT",
    "tagName": "MY_ARRAY",
    "arrayLength": 10,
    "pollingInterval": 1000,
    "transform": {
        "VALUE_1": "#valueof($.input[0])",
        "VALUE_2": "#valueof($.input[1])",
        "VALUE_3": "#valueof($.input[2])",
        "VALUE_4": "#valueof($.input[3])",
        "VALUE_5": "#valueof($.input[4])",
        "VALUE_6": "#valueof($.input[5])",
        ...
    }
}

Credits

This project leverages on https://github.com/libplctag/libplctag.NET to provide connectivity to the PLC devices.

License

This project is licensed under the MIT License (see ./LICENSE.md) for more details.