Bitpool Edge Modbus

A Node-RED node to communicate with Modbus equipment

Getting Started

This is a standard Node.js module developed specifically to function within the Node-RED ecosystem.

How to Use

Use the following procedure to install this module to your Node-RED instance, or download the pre-themed Bitpool-Edge Docker image that contains all our favourite nodes pre-installed.

Bitpool-Edge Install

1. Log into your Bitpool-Edge instance and click the Hamburger icon, in the top-right corner.

2. Select Manage Palette from the drop down menu then click the Pallete->Install tabs to install.

3. Using the search bar type @bitpoolos/edge-modbus and install the module once displayed.

4. Finally, use the left most navigation menu to scroll down to the heading Bitpool Modbus to reveal available nodes.

Docker Install 🐳

This Modbus module and many other Bitpool developed nodes have been pre-installed for your convenience in a Bitpool themed Node-RED application.

Go here for how to install Bitpool-Edge.

Modbus Nodes

The Modbus library of nodes is broken down into 4x functional blocks.

1. device - allows us to create a virtual map of a target Modbus device.

2. reader - defines a communication pathway to a Modbus device(s).

3. decoder - ensures that returned Modbus register data is correctly formatted.

4. display - is an optional component to visualise data for a unique Modbus register.

Basic Workflow

The image above here is an example of linked Modbus nodes on a Flow tab. This is the basic flow of data.

1. The ‘Trigger’ node injects a simple timestamp into the device node 'ABB B23 B24'.

2. The device node contains a list of Modbus registers with associated information which is sent to the reader node ‘Modbus Con’.

3. The reader node queues each Modbus register request and manages serial bus arbitration. Each response is then sent to the decoder node ‘Decoder’.

4. The decoder node handles each request using information stored in the JSON object. This is converted to the correct format as a topic/value pair, then sent to the output.

5. Finally, the display node prints the payload to it status field for the user to see.

Basic Workflow Node Properties

• Trigger - this is a standard inject node and is used to initiate a Modbus read.

  • Payload - set as timestamp but can be any value.

  • Topic - not used.

• Device - description of the target Modbus device.

  • Name - any meaningful description.

  • Modbus ID - the numeric value of the Modbus address.

  • Registers

    • Template - the drop-down allows the user to select a predefined templates of Modbus registers. This is a cloud service and is only available if the system has Internet access. An alternative solution is to manage templates via the upload/download templates buttons.

    • Load – the selected template will be loaded into the Modbus Map

    • Filters

      • By Name - filters user input matching the Name.

      • By Address - filters user input matching the Modbus address.

    • Register

      • Name (mandatory) – forms part of topic structure.

      • Address (mandatory) - address of the Modbus register.

      • Code (mandatory) - Modbus register type (Coil, Register)

      • Multiplier (mandatory) - normally set to 1 (applied to output of Decoder node).

      • Size (mandatory) - vendor specific setting of register data size (applied to output of Decoder node).

      • Format (mandatory) - vendor specific setting of register format (applied to output of Decoder node).

      • Unit Name (optional) - supplemental Unit of Measure field for Display node (e.g. 100Wh).

      • Unit Scale (optional) - supplemental scaling prefix for Display node for (e.g. 100kWh).

    • Buttons

      • Add - adds a register block to the Register Map.

      • Delete - deletes all register blocks from Register Map.

      • Upload - allows a user to upload a previously saved Register Map from the local file system.

      • Download - allows a user to download the current Register Map to the local file system.

      • View - opens browser tab to provide a view of the current Register Map, formatted as JSON.

    • Options

      • General

        • Group Reads - option to optimize the number of Modbus request being made. A single request can return multiple values if the registers are in a contiguous block.

      • Monitoring

        • Activity - option to show the node activity.

        • Warnings - option to output warnings to the debug tab.

• Reader - defines the client-side connection to the Modbus network.

  • Name - any meaningful description of the reader node.

  • Connection

    • Name - any meaningful description of the new client.

    • Type - the connection type to either network socket or serial port.

    • Unit ID - allows multiple nodes to independently share the same Modbus network.

    • Timeout - number of milliseconds the node will wait before a timeout exception is raised.

    • Reconnect - number of milliseconds the node will wait after a timeout exception, before reattempting a connect.

    • Queue Delay - number of milliseconds the node will wait between sending Modbus register requests.

    • Activity - shows the status of the connection to the debug tab.

• Decoder - converts packets received from Modbus network to those defined in the Device node (factoring, byte resizing and reordering)

  • Options

    • Monitoring

      • Activity - shows activity of the node.

      • Warnings - outputs any node warnings to the debug tab.

    • Converting

      • Power Factor - option to convert multi quadrant values (-2,-1,0,1, 2) to absolute (0-1).

      • Reals - fixes all decimal point values to 3 significant places.

• Display - selected Modbus register values will be displayed.

  • Name - any meaningful description.

  • Register - text field to manually add the Modbus register, if known.

  • Auto-Fill Device - selection to automatically discover upstream Device node.

  • Auto-Fill Register - selection to automatically discover upstream Register name of the Device node.

  • Options

    • Warnings - option to output any node warnings to the debug tab.

Further Information

Now that your Bitpool-Edge is up and running, we have included simple examples flows to demonstrate how to create a basic solution.

1. Log into your Bitpool-Edge instance and click the Hamburger icon, in the top-right corner.

2. Select Manage Palette from the drop down menu then click the Import->Examples tabs to see this node.

3. Navigate the ‘Examples flows’ tree and select @bitpoolos/edge-modbus to reveal the preconfigured examples.

4. Click the example you would like to test the click the Import button.

5. Place the example nodes on a flow and review the configuration of each node. You will need to make suitable changes for your system.

6. Finally, click the Save to test.

Additionally, there is basic helper documentation on each node. Just select a target node and click the Help tab found at the top right corner of Bitpool-Edge.

Hint - the icon looks like a book!