Presentation of the personal project for pervasive systems course

1. A visual tool for wiring the internet of things
David Ghedalia

2. Flow-based programming
• An application constits of a set of blocks
• The programmer treats each block as a blackbox
• Knowing the implementation details is not necessary
• Each block has one or more ports (in input, output or
both) to communicate with other blocks
• The communication is message-based

3. IoT and visual programming
The very nature of flow-based programming leads to two
major consequences:
• It can be easily implemented in a visual manner,
allowing the development of complex applications
in a short period of time
• Pardigm is particularly suitable for an IoT environment, in which
a large amount of computation is used to exchange messages

4. What is Node-RED?
• Node-RED is a flow-based development tool developed originally by
IBM for wiring together hardware devices, APIs and online services as
part of the Internet of Things
• Thanks to its intuitive browser-based flow
editor, Node-RED gives the possibility to
build applications even to non programmers

5. The architecture
• Runtime
It is written in Javascript and based on NodeJS, taking full advantage of its
event-driven, non-blocking model
• UI
Written in HTML and JavaScript: it enables to
build flows in a visual manner

6. Other features
• Node-RED is open source
• Simple and fast to deploy
• Flows stored as a JSON file
In this way, they can be easily shared
• Thousands of custom nodes (and flows) built by the community

7. Getting started

8. Launching Node-RED
• After the installation (requires NodeJS),
open the command prompt and digit:
«node-red»
• To access the editor, open the browser and
go to localhost at port 1880

9. Building the first flow (1)
In the main page of Node-RED, there are three major sections
Node palette on the left
• At first, it will contain the core nodes only
• The nodes are organized in categories
The main work space on the center
Output pane on the right
• Useful for getting info about the
selected node
• Here you can find the debug section

10. Building the first flow (2)
• To insert a node in the current flow, drag a node from the palette and
drop it into the workspace
• To edit a node, double-click on it: a pane will appear, containing all
the editable settings.
In certain nodes, one or more fields will be required before being able to
deploy the flow
• To link two nodes, click and hold the output port of the first node and
release at the input port of the second node

11. Building the first flow (3)
• Click deploy to make the flow run

12. The project

13. Description
home/switchLed
home/ledStatus
MQTT client
MQTT client
+
MQTT broker
NodeMCU
Raspberry Pi
• NodeMCU acts as an MQTT client: it subscribes to topic «home/switchLed»
and publishes to topic «home/ledStatus»
• Raspberry Pi is both an MQTT client and MQTT broker. NodeRED will provide:
A graphical interface to switch the led on and off (running at localhost:1880/ui/)
A log file that will be updated each time that the led is turned on or off•
HTTP
HTTP

14. Flow

15. Flow (1)

16. Flow (2)

17. Flow (3)
Javascript function

18. MQTT Client for NodeMCU

20. Conclusions
• As you can see, there is a lot more work involved to handle the MQTT
protocol compared to Node-RED
• Node-RED is very good for rapid prototyping and building demos
• Node-RED helps you to focus on the main goal of the app rather than
on the implementation details

21. Thanks!