Setting up an IoT

Session 3: MQTT and Cayenne

Uli Raich

Formally CERN, Geneva, Switzerland

Slide 1 of 55

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 55

Accessing the WiFi network

Slide 3 of 55

Accessing the WiFi network from Micropython

Slide 4 of 55

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 55

MQTT Demo

Slide 6 of 55

The Micropython library

Slide 7 of 55

A MQTT example using umqtt.simple

Slide 8 of 55

Sending dummy temperature data

Slide 9 of 55

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 55

Subscribe a callback

Slide 11 of 55

Callback result

Slide 12 of 55

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 55

Changed Callback

Slide 14 of 55

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 55

Cayenne functionality

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

Slide 16 of 55

Signing up for Cayenne

Slide 17 of 55

Cayenne Start

Slide 18 of 55

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 55

Installing Cayenne on the Raspberry PI

Slide 20 of 55

Installing Cayenne on the Raspberry Pi manually

Slide 21 of 55

Slide 22 of 55

Run Cayenne on the Arduino

Slide 23 of 55

Basic Arduino Sketch for the Arduino

Slide 24 of 55

Cayenne Credentials

Slide 25 of 55

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 55

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 55

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 55

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 55

The code to connect to Cayenne

Slide 30 of 55

Connecting to Cayenne

Slide 31 of 55

The empty Cayenne dashboard

Slide 32 of 55

Send dummy measurement

Slide 33 of 55

Dummy temperature in Cayenne

Slide 34 of 55

Dummy temperature parameters

Slide 35 of 55

Fix widget to dashboard

Slide 36 of 55

Dummy temperature history

Cayenne keeps measurement values which can be plotted as a history plot

or downloaded for further evaluation

Slide 37 of 55

A custom widget

Slide 38 of 55

A gauge widget

Slide 39 of 55

Dummy temperature gauge on the dashboard

Slide 40 of 55

Gauge value ranges

Slide 41 of 55

It's hot!

Slide 42 of 55

Several dummy measurements

Now we want to send a dummy temperature and a dummy humidity value.

How do we distinguish?

They use different communication channels!

Slide 43 of 55

Sending temperature and humidity: the code

Slide 44 of 55

Dashboard with temperature and humidity

Slide 45 of 55

Other measurements

We have seen that we can send temperature with

client.celsiusWrite(channel,temp)

And relative humidity with

Client.humidityWrite(channel,hum)

Which other types of measurements can we send?

Slide 46 of 55

Measurements implemented in the Cayenne Client

Slide 47 of 55

How to control a device?

Cayenne supplies only 2 control widgets:

a push button
A slider

Slide 48 of 55

Cayenne Slider

We can define the range for the slider in the above case: 0..255

Slide 49 of 55

Slider on the dashboard

Slide 50 of 55

A Cayenne Button

Slide 51 of 55

Dashboard with button

Slide 52 of 55

How to receive commands

We must define a callback function, which is called

whenever the user of the Cayenne dashboard

changes a setting on the push button or slider

The callback takes a message parameter which is a tuple of

Cayenne topic
Cayenne payload

Slide 53 of 55

Cayenne command message

Please compare the command message with our credentials and try to find out

to which channel this command has been addressed. Can you find the values as well?

Remember: we defined the push button on channel 3 and the slider in channel 2!

Slide 54 of 55

Exercises!

More on how to interpret this message in the next session

Slide 55 of 55

-- 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	cayenneCmdMsg.png	r1	manage	189.5 K	2019-05-22 - 19:15	UliRaich
png	cayenneCmdMsg2.png	r1	manage	68.6 K	2019-05-22 - 19:15	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	cayenneCustonWidget.png	r1	manage	184.8 K	2019-05-22 - 19:26	UliRaich
png	cayenneDashButton.png	r1	manage	156.5 K	2019-05-22 - 19:03	UliRaich
png	cayenneDashSlider.png	r1	manage	139.6 K	2019-05-22 - 19:03	UliRaich
png	cayenneDashboardTempHum.png	r1	manage	119.5 K	2019-05-22 - 18:56	UliRaich
png	cayenneDoc.png	r1	manage	158.3 K	2019-05-22 - 16:21	UliRaich
png	cayenneDummyButtton.png	r1	manage	211.0 K	2019-05-22 - 19:04	UliRaich
png	cayenneDummySlider.png	r1	manage	178.5 K	2019-05-22 - 19:04	UliRaich
png	cayenneDummyTemp.png	r1	manage	71.1 K	2019-05-22 - 18:32	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	cayenneGaugeRanges.png	r1	manage	155.2 K	2019-05-22 - 18:48	UliRaich
png	cayenneHot.png	r1	manage	147.2 K	2019-05-22 - 18:32	UliRaich
png	cayenneMQTTCalls.png	r1	manage	67.0 K	2019-05-22 - 18:56	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	cayenneTempGauge.png	r1	manage	205.1 K	2019-05-22 - 18:41	UliRaich
png	cayenneTempHum.png	r1	manage	82.7 K	2019-05-22 - 18:52	UliRaich
png	cayenneWarm.png	r1	manage	149.6 K	2019-05-22 - 18:44	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	dummyTemp.png	r1	manage	110.2 K	2019-05-22 - 18:32	UliRaich
png	dummyTempFixed.png	r1	manage	126.3 K	2019-05-22 - 18:32	UliRaich
png	dummyTempHistory.png	r1	manage	29.5 K	2019-05-22 - 18:32	UliRaich
png	dummyTempPars.png	r1	manage	137.8 K	2019-05-22 - 18:37	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	ourCredentials.png	r1	manage	17.9 K	2019-05-22 - 19:15	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: r9 - 2019-05-22 - UliRaich

Session 3: MQTT and Cayenne

Uli RaichFormally CERN, Geneva, Switzerland

Comments

Uli Raich

Formally CERN, Geneva, Switzerland