My Modbus Working Notes

I have developed a few flows for third parties that have mainly involved decoding Modbus data. However I have never used Modbus in a live environment and needed to get familiar with the basics in order to develop and test these flows. Fortunately the people I worked with had a very good understanding of Modbus, but not of node-red, JavaScript and MQTT These are my working notes from my efforts to create these flows and in particular an MQTT to Modbus bridge. If you are new to Modbus you may find them useful. Click to rate this post! [Total: 2 Average: 5]

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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. Click to rate this post! [Total: 2 Average: 5]

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Node-Red – Storing IOT Data in a SQL Database

IOT data from sensors and other devices usually comes as either a text string usually with key value pairs or more commonly as JSON encoded data. Databases accept a variety of data formats the most common are INT and TEXT. Click to rate this post! [Total: 3 Average: 5]

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Beginners Guide to the Node-Red Settings.js File

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. Click to rate this post! [Total: 1 Average: 5]

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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. Click to rate this post! [Total: 0 Average: 0]

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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. Click to rate this post! [Total: 2 Average: 4.5]

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Understanding and Using Buffers In Node-Red

When data is read from a file or network it is read byte by byte into a data buffer. Data Buffers are temporary storage used for transferring data. To work with binary data we will need access to these buffers. Click to rate this post! [Total: 3 Average: 5]

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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 Click to rate this post! [Total: 2 Average: 4]

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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. Click to rate this post! [Total: 1 Average: 5]

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Node-Red HTTP Request Node for Beginners

In node-red there are three core http nodes. http-in -Used to configure a web server http response – used with http-in to send responses. http request – used for making http requests i.e an http client. The http request node can be used for. Retrieving web pages from a website Making API Requests Sending and receiving JSON data to a website or API. etc The node will send a request and receive the response. The request node handles both the request and the  response. Note: if you are not familiar with the http protocol then I suggest you read the http basics tutorial. Click to rate this post! [Total: 2 Average: 5]

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