Node-RED introduction - Revision history

EdmondLascaris: /* 4. Opening the Node-RED interface using a Web Browser */

2021-12-31T05:51:29Z

4. Opening the Node-RED interface using a Web Browser

← Older revision		Revision as of 05:51, 31 December 2021
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	[[File:Screen Shot 2021-12-31 at 4.08.36 pm.png]]		[[File:Screen Shot 2021-12-31 at 4.08.36 pm.png]]

	=== 4. Opening the Node-RED interface using a Web Browser ===		=== Opening the Node-RED interface using a Web Browser ===
	* Open the default web browser on the Raspberry Pi		* Open the default web browser on the Raspberry Pi
	* In the Search bar enter the URL '''localhost:1880'''		* In the Search bar enter the URL '''localhost:1880'''

EdmondLascaris: /* Creating your first flow */

2021-12-31T05:51:07Z

Creating your first flow

← Older revision		Revision as of 05:51, 31 December 2021
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	* In this case the timestamp is the number of milliseconds from 1st January 1970 – '''1634681792235'''.		* In this case the timestamp is the number of milliseconds from 1st January 1970 – '''1634681792235'''.
	* You can test this by pressing the inject button once every second to see how the number increments.		* You can test this by pressing the inject button once every second to see how the number increments.

			[[File:Screen Shot 2021-12-31 at 4.43.18 pm.png]]

			=== Executing Python programs using Node-RED exec node ===
			* Drag the inject, debug and exec nodes into the Editor window and connect them with wires as shown.

			[[File:Screen Shot 2021-12-31 at 4.44.22 pm.png]]

			* The exec node has three outputs:
			** first – '''standard output''' like the output in the Python Shell or Terminal + return code
			** second – '''error output''' + return code
			** third – '''return code''' (rc). Any return code above 0 is an error.

			* Double click on the '''exec node''' to bring up the '''Edit exec node''' window.

			[[File:Screen Shot 2021-12-31 at 4.46.02 pm.png]]

			* In the Command line enter the following two part statement:
			** '''cd /home/pi/peter-hopper-t3''' – change directory giving absolute path reference
			** '''python3 peter_hopper_get_data.py''' – run the program using python3
			* Set all other settings as shown then click on the red button '''Done'''.

			[[File:Screen Shot 2021-12-31 at 4.47.13 pm.png]]

			* When you return to the editor window you may need to re-arrange your nodes.
			* Then click on the Deploy button to run your program.

			[[File:Screen Shot 2021-12-31 at 4.48.06 pm.png]]

			* To run the program, click on the '''grey''' button the '''inject node'''.
			* This will inject a timestamp message (msg.payload).
			* This has the effect of '''triggering the exec code''' and making your python program run.
			* On the right hand side in the debug window you will see the standard output from your program and any error messages.

			[[File:Screen Shot 2021-12-31 at 4.49.36 pm.png]]

			* In the debug window, clicking on the arrow on the left of the '''standard output''' will expand the '''msg.payload'''.
			* In this example we can see the standard output from the python program.
			* The '''return code''' is 0 which indicates no errors.

			[[File:Screen Shot 2021-12-31 at 4.50.47 pm.png]]

			* Congratulations for completing your first program in Node-RED.
			* In future lessons we will learn how to chart data using the Node-RED Dashboard.

EdmondLascaris: /* Creating your first flow */

2021-12-31T05:18:16Z

Creating your first flow

← Older revision		Revision as of 05:18, 31 December 2021
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	* A '''timestamp''' in computers is a representation of the amount of time that has passed since '''1st January 1970'''.		* A '''timestamp''' in computers is a representation of the amount of time that has passed since '''1st January 1970'''.
	* In this case the timestamp is the number of milliseconds from 1st January 1970 – '''1634681792235'''.		* In this case the timestamp is the number of milliseconds from 1st January 1970 – '''1634681792235'''.
			* You can test this by pressing the inject button once every second to see how the number increments.

EdmondLascaris: /* 4. Opening the Node-RED interface using a Web Browser */

2021-12-31T05:17:45Z

4. Opening the Node-RED interface using a Web Browser

@@ Line 75: / Line 75: @@
 === 4. Opening the Node-RED interface using a Web Browser ===
-Open the default web browser on the Raspberry Pi
+* Open the default web browser on the Raspberry Pi
-In the Search bar enter the URL localhost:1880
+* In the Search bar enter the URL '''localhost:1880'''

EdmondLascaris: /* Run the python file peter_hopper_get_data.py */

2021-12-31T05:09:16Z

Run the python file peter_hopper_get_data.py

← Older revision		Revision as of 05:09, 31 December 2021
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	[[File:Screen Shot 2021-12-31 at 3.44.31 pm.png]]		[[File:Screen Shot 2021-12-31 at 3.44.31 pm.png]]

			* Note the very first line that shows:
			** '''/home/pi/peter-hopper-t3/''' – the full path of the file
			** '''peter_hopper_get_data.py''' – the file name
			* We will need to use this information later when coding Node-RED.

			[[File:Screen Shot 2021-12-31 at 3.57.14 pm.png]]

			=== Finding the path and name of a file in the Terminal ===
			* Open the '''Terminal'''.
			* Enter the command '''ls''' to list all directory contents.
			* Then enter the command '''pwd''' – which gives the path to the '''present working directory'''
			* In this example the path to the pi directory is '''/home/pi'''

			[[File:Screen Shot 2021-12-31 at 4.00.02 pm.png]]

			* To change directory and enter the peter-hopper-t3 enter the command '''cd peter-hopper-t3'''
			* To list all the contents of the peter-hopper-t3 directory enter '''ls'''
			* To determine the full path to this directory enter '''pwd'''
			* Notice that the path is the same as the output in the Python Shell.

			[[File:Screen Shot 2021-12-31 at 4.02.51 pm.png]]

			* To run the peter_hopper_get_data.py file enter '''python3 peter_hopper_get_data.py'''

			[[File:Screen Shot 2021-12-31 at 4.03.48 pm.png]]

			* The program output that we typically see in the Python Shell is now in the Terminal.

			[[File:Screen Shot 2021-12-31 at 4.04.38 pm.png]]

			=== Starting Node-RED ===
			* To start Node-RED open the Terminal and enter the command Node-RED

			[[File:Screen Shot 2021-12-31 at 4.06.17 pm.png]]

			* You should see an output similar to below.
			* I have some additional programs already running in Node-RED, so my display will be different.

			[[File:Screen Shot 2021-12-31 at 4.07.06 pm.png]]

			* Before shutting down the Raspberry Pi you should always stop Node-RED.
			* Open a new Terminal window and enter '''node-red-stop'''
			* If you need to restart Node-RED enter '''node-red''' or '''node-red-start'''

			[[File:Screen Shot 2021-12-31 at 4.08.36 pm.png]]

			=== 4. Opening the Node-RED interface using a Web Browser ===
			Open the default web browser on the Raspberry Pi
			In the Search bar enter the URL localhost:1880

EdmondLascaris: /* Run the python file peter_hopper_get_data.py */

2021-12-31T04:45:11Z

Run the python file peter_hopper_get_data.py

← Older revision		Revision as of 04:45, 31 December 2021
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	[[File:Screen Shot 2021-12-31 at 3.41.21 pm.png]]		[[File:Screen Shot 2021-12-31 at 3.41.21 pm.png]]
			[[File:Screen Shot 2021-12-31 at 3.43.35 pm.png]]

			* Run the program by selecting Run > Run module.
			* The program will send output to the Python Shell.
			* A typical output in the Shell is presented below.

			[[File:Screen Shot 2021-12-31 at 3.44.31 pm.png]]

EdmondLascaris at 04:42, 31 December 2021

2021-12-31T04:42:01Z

← Older revision		Revision as of 04:42, 31 December 2021
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	* Learn how to start node-red on the Raspberry Pi.		* Learn how to start node-red on the Raspberry Pi.
	* Learn how to run Python programs in Node-RED.		* Learn how to run Python programs in Node-RED.

			== Introduction to Node-RED on the raspberry Pi ==
			* Node-RED is a powerful and intuitive programming language pre-installed on the Raspberry Pi.
			* This lesson will serve as an introduction to the use of this platform.
			* In this lesson we will learn how to execute python programs.

			=== Run the python file peter_hopper_get_data.py ===
			* From the main Raspberry Pi menu navigate to Programming and open '''Python3 IDLE'''
			* Open the saved file peter_hopper_get_data.py
			* The full listing is below.

			[[File:Screen Shot 2021-12-31 at 3.41.21 pm.png]]

EdmondLascaris: Created page with "== Overview == * The aim of this lesson is to start learning to use '''Node-RED''' which is a block-based programming language. * The appeal of Node-RED is that individual code segments are hidden in nodes. * Individual nodes can be connected using wires. * This makes the program much easier to '''visualise''' and program. == Learning Objectives == * Learn how to start node-red on the Raspberry Pi. * Learn how to run Python programs in Node-RED."

2021-12-31T04:39:20Z

Created page with "== Overview == * The aim of this lesson is to start learning to use '''Node-RED''' which is a block-based programming language. * The appeal of Node-RED is that individual code segments are hidden in nodes. * Individual nodes can be connected using wires. * This makes the program much easier to '''visualise''' and program. == Learning Objectives == * Learn how to start node-red on the Raspberry Pi. * Learn how to run Python programs in Node-RED."

New page

== Overview ==
* The aim of this lesson is to start learning to use '''Node-RED''' which is a block-based programming language.
* The appeal of Node-RED is that individual code segments are hidden in nodes.
* Individual nodes can be connected using wires.
* This makes the program much easier to '''visualise''' and program.

== Learning Objectives ==
* Learn how to start node-red on the Raspberry Pi.
* Learn how to run Python programs in Node-RED.