Setting up an IoT

Session 3: MQTT and Cayenne

Uli Raich

Formally CERN, Geneva, Switzerland

Slide 1 of 32

The Network Layers

The WeMos D1 mini has a built-in WiFi interface

In order to communicate with other IoT nodes we must therefore

connect to the WiFi network first

On top of WiFi we will run a TCP session

On top of TCP we will run the MQTT protocol

On top of MQTT we have dedicated topics and payloads imposed by Cayenne

Slide 2 of 32

Accessing the WiFi network

Slide 3 of 32

Accessing the WiFi network from Micropython

Slide 4 of 32

MQTT

MQTT (Message Queuing Telemetry Transport: a publish-subscribe based

message protocol running of top of TCP.

A processor can subscribe to messages of a certain “topic” and/or it can push its

results on a certain topic

Slide 5 of 32

MQTT Demo

Slide 6 of 32

The Micropython library

Slide 7 of 32

A MQTT example using umqtt.simple

Slide 8 of 32

Sending dummy temperature data

Slide 9 of 32

Receiving commands

Receiving commands is a bit more tricky! We must:

Write a callback function and register it with the MQTT client
This function takes 2 arguments:
The topic
The payload
Subscribe to the topic
Wait forever. The callback function will be executed when a message with the
topic we subscribed to, will arrive

Slide 10 of 32

Subscribe a callback

Slide 11 of 32

Callback result

Slide 12 of 32

Controlling a LED

In order to control a LED through MQTT we now simply interpret the payload:

Message “LED on”
Message “LED off”

Slide 13 of 32

Changed Callback

Slide 14 of 32

Missing functions in IoT

MQTT broker should be globally reachable
GUI to easily visualize sensor measurements
GUI elements to easily control actuators
GUI should be accessible through a WEB interface
GUI should be accessible through smart phone app

This is what Cayenne supplies

Slide 15 of 32

Cayenne functionality

MQTT broker is accessible at mqtt.mydevices.com
Supplies GUI

Slide 16 of 32

Signing up for Cayenne

Slide 17 of 32

Cayenne Start

Slide 18 of 32

Cayenne Doc

You find the documentation at

https://mydevices.com/cayenne/docs/intro

Contains short introductory video clips, information of Cayenne on Raspberry Pi and Arduino but also how to use Cayenne on any device.

Pointers to the Cayenne MQTT Libraries and their API

Slide 19 of 32

Installing Cayenne on the Raspberry PI

Slide 20 of 32

Installing Cayenne on the Raspberry Pi manually

Slide 21 of 32

Slide 22 of 32

Run Cayenne on the Arduino

Slide 23 of 32

Basic Arduino Sketch for the Arduino

Slide 24 of 32

Cayenne Credentials

Slide 25 of 32

Cayenne network layers

The Cayenne credentials are integrated into the MQTT topic string

Value and units are integrated into the payload string

Slide 26 of 32

Cayenne and Python

This falls under “bring your own thing” !

Having a look at the Arduino sketch you can see that it uses the

Arduino Cayenne C++ library.

Cayenne MQTT libraries are available in

C, C++
Python
Java

and probably a few other languages

Slide 27 of 32

Cayenne and Micropython

The Python Cayenne Client library depends on the Eclipse Paho MQTT library

Micropython uses its own, stripped down “umqtt” (micro mqtt) library

such that the standard Cayenne Client does not work on Micropython

but …

The Python Cayenne Client is Open Source and can be adapted to umqtt, which is what I did for you.

The adapted Client library uses the same API as the original one,

which means that the example programs work unchanged.

Slide 28 of 32

The Cayenne Client

When creating a Cayenne Client Class it

Initializes its internal variables
Checks if the OLED display is connected and if yes, initializes it
The Cayenne Client has has a begin method which
Connects to WiFi
Connects to the Cayenne MQTT broker at mqtt.mydevices.com
Subscribes to commands send by Cayenne
Displays its internal state on the OLED display

Slide 29 of 32

The code to connect to Cayenne

Slide 30 of 32

Connecting to Cayenne

Slide 31 of 32

The empty Cayenne dashboard

Slide 32 of 32

-- Uli Raich - 2019-05-14

Comments

I	Attachment	History	Action	Size	Date	Who
odp	afnog19-ws-session3.odp	r1	manage	5245.0 K	2019-05-15 - 19:13	UliRaich
png	callbackResult.png	r1	manage	142.7 K	2019-05-22 - 12:31	UliRaich
png	cayenneArduinoInstall.png	r1	manage	128.4 K	2019-05-22 - 16:32	UliRaich
png	cayenneArduinoSketch.png	r1	manage	191.2 K	2019-05-22 - 16:35	UliRaich
png	cayenneConnect.png	r1	manage	137.9 K	2019-05-22 - 16:52	UliRaich
png	cayenneConnectCode.png	r1	manage	56.8 K	2019-05-22 - 16:52	UliRaich
png	cayenneCredentials.png	r1	manage	109.7 K	2019-05-22 - 16:36	UliRaich
png	cayenneDoc.png	r1	manage	158.3 K	2019-05-22 - 16:21	UliRaich
png	cayenneEmptyDashboard.png	r1	manage	150.2 K	2019-05-22 - 16:52	UliRaich
png	cayenneFunctionality.png	r1	manage	135.7 K	2019-05-22 - 16:09	UliRaich
png	cayenneNetLayers.png	r1	manage	34.5 K	2019-05-22 - 16:45	UliRaich
png	cayenneRPI.png	r1	manage	150.8 K	2019-05-22 - 16:24	UliRaich
png	cayenneRegisterRPI.png	r1	manage	148.3 K	2019-05-22 - 16:24	UliRaich
png	cayenneSignup.png	r1	manage	122.2 K	2019-05-22 - 16:15	UliRaich
png	cayenneStart.png	r1	manage	146.3 K	2019-05-22 - 16:15	UliRaich
png	cayenne_RPI_ManualInstallation.png	r1	manage	189.9 K	2019-05-22 - 16:30	UliRaich
png	changedCallback.png	r1	manage	15.3 K	2019-05-22 - 16:06	UliRaich
png	micropython-lib.png	r1	manage	75.2 K	2019-05-14 - 17:31	UliRaich
png	mqttDemo.png	r1	manage	191.3 K	2019-05-14 - 17:23	UliRaich
png	mqttDummySensorDemo.png	r1	manage	74.4 K	2019-05-20 - 18:40	UliRaich
png	mqttExample.png	r2 r1	manage	73.2 K	2019-05-15 - 16:12	UliRaich
png	mqttPostOfffice.png	r1	manage	50.2 K	2019-05-14 - 17:18	UliRaich
png	realData.png	r1	manage	27.7 K	2019-05-15 - 17:12	UliRaich
png	subscribeDemo.png	r1	manage	78.3 K	2019-05-20 - 18:45	UliRaich
png	umqttDemo.png	r2 r1	manage	72.2 K	2019-05-14 - 17:38	UliRaich
png	wifiConnect.png	r1	manage	128.4 K	2019-05-14 - 17:18	UliRaich
png	wifiDemoCode.png	r1	manage	43.8 K	2019-05-15 - 16:14	UliRaich

This topic: AFNOG > WebHome > AFNOGWorkshop2019 > AFNOG-2019Slides > WorkshopSlides > MQTTAndCayenne
Topic revision: r8 - 2019-05-22 - UliRaich

Session 3: MQTT and Cayenne

Uli RaichFormally CERN, Geneva, Switzerland

Comments

Uli Raich

Formally CERN, Geneva, Switzerland