Modbus MQTT and Node-Red

Modbus is a de facto standard, truly open and the most widely used network protocol in the industrial manufacturing environment.-ref Modbus Faqs Because of its popularity there is a growing requirement for reading data and controlling Modbus devices over TCP/IP networks using MQTT.

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Using the Node-Red Template Node

There are two template nodes in node-red. They are the HTML template node and the dashboard template node. In this tutorial we will discuss the HTML template node which is a core node, and is located in the function section.

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Node-Red Initialising Flow Data on Startup

Often you want your flow to start with known conditions. For example you may have a flow that records various sensors and have alarms set when the sensors exceed a given value. As an example you may want to trigger an alarm when the temperature falls below 3 degrees or exceeds 30 degrees Centigrade.

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Node-Red Settings.js File – Node-Red Admin

Node red uses a settings file called settings.js located in in the user .node-red (dot node-red) folder in their home directory. You can create your own settings file and customise it either by copying the existing file or using the file available from Github here. On Linux the settings.js file is copied from the /usr/lib/node-modules/node-red/ folder to your .node-red folder in your home directory when you start node-red, and there is no settings.js file present.

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Using The Node-Red Library

If you want to save a flow or function and reuse it later in another flow on the same computer then you can save it to the local library. To save a flow to the library highlight all nodes in the flow by using CTRL+A then use the main menu (top right) and select Export>Library.

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Deploying Node-Red Flows

When you come to deploying a flow you have four (node-red v0.2)options as shown below: Although the choices appear obvious the effect of the options isn’t and can cause some confusion.

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Working with JSON Data And JavaScript Objects in Node-Red

JSON is popular format for encoding data sent over the Internet, and also stored in files. In computing, JavaScript Object Notation (JSON) is an open-standard file format that uses human-readable text to transmit data objects consisting of attribute–value pairs and array data types (or any other serializable value). –wiki

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Using the Node Red Status Node

In Node red any node can report status information in the visual editor. The screen shot below shows the mqtt node. It shows a green circle to indicate that it is connected and the text connected underneath the node.

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