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IoT Workshop

Trygve Laugstøl <trygvis@trygvis.io>

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What is IoT

Not “a computer connected to the internet” -
- Then it is really just another computer connected to the internet
Must be something else -
- It is simply devices that are resource constrained -
  - Usually in more than one way
Autonomous operation, the connection might not be permanent

IoT is just a concept

The Internet of Things (IoT) is the network of physical devices, vehicles, home appliances and other items embedded with electronics, software, sensors, actuators, and connectivity which enables these objects to connect and exchange data.¹

What is an IoT Device?

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What is an IoT Device?

Constrained in (one or more of): -
- Memory
- CPU
- Network bandwidth and/or latency
- Storage
Connected -
- Bluetooth
- Wi-Fi
- NB-IoT
- LTE Cat-M
- IR
- UART
- CAN

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Typical IoT chips - Bluetooth 4/5

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Chip	CPU	Freq	RAM	Flash	Price
nRF52810	Cortex-M4	64 M	Hz 24k	192k	$1.88
High perf	ormance,	entry	-level Bl	uetooth	4/ANT/2.4GHz SoC

nRF52832 Cortex-M4F 32k 256k $2.54 64k 512k $2.59 High performance Bluetooth 4/ANT/2.4GHz SoC

nRF52840 Cortex-M4F 256k 1024k $3.85 Advanced multi-protocol System-on-Chip Supporting: Bluetooth 5, ANT/ANT+, 802.15.4 and 2.4GHz proprietary

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Typical IoT chips - Wi-Fi

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Chip	CPU	Freq	ROM	RAM	Price
ESP8266	Tensilica L106	160 MHz	N/A	~50 kB	< $1

ESP32 - dual cpu, Wi-Fi, Bluetooth 4 ESP32-D0WDQ6 2x Xtensa @ 160MHz $ 4.53 @ 10

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ESP8266 details - Power usage

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State	Current usage
Off	0.5 µA
Deep sleep with RTC	20 µA
Light sleep (with Wi-Fi)	1 mA
Sleep with peripherials	15 mA
TX	170 mA

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ESP8266 details - Arduino

https://github.com/esp8266/Arduino

Going back to basics

What is the internet again?

OSI model

Physical Layer
Data Link Layer
Network Layer
Transport Layer
Session Layer
Presentation Layer
Application Layer

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Layer 1: Physical Layer

10BASE5, 10BASE2
10BASE-T / 100BASE-TX / 1000BASE-TX
802.11a/b/g/n PHY
RS-232

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Layer 2: Data Link Layer

Ethernet
WiFi
Bluetooth
Token Ring

Layer 3: Network Layer

IP
ICMP
IPX

Layer 4: Transport Layer

Layer 5: Session Layer

“sockets”
NetBIOS

Layer 6: Presentation Layer

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Layer 7: Application Layer

HTTP
DNS
MQTT
CoAP
(everything else..)

Details: IP

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Details: IP

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Lecture: ESP8266

ESP8266 software layers

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Lecture: MQTT

MQTT

Message Queuing Telemetry Transport
Wikipedia: MQTT

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MQTT - The protocol

Agents have one of two roles:

Client -
- Publishes messages
- Subscribes / unsubscribes to topics
Broker (aka Server) -
- Handles network connections
- Keeps subscriptions
- Manages client -
  - Disconnects
  - (last) will
- Persistence of retained messages

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MQTT - The protocol - MQTT Topic

Topic name: foo/bar/baz
Topic filter -
- foo/bar/?
- foo/#

MQTT - The protocol - MQTT Topic

The temperature sensor:

Publishes on: -
- myapp/$device-id/temperature
- myapp/$device-id/humidity
- myapp/$device-id/altert
Subscribes to: -
- myapp/$device-id/command

The central application:

Subscribes to: -
- myapp/#/temperature
- myapp/#/humidity
Publishes on: -
- myapp/$device-id/command

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MQTT - The protocol - MQTT Packet

Size oriented
Flags indicate type of remaining bytes -
- Packet type
- Topic name
- Payload

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MQTT - The protocol - MQTT Topic - more

Enten må den holdes rett etter “## MQTT - The protocol - MQTT Topic” ellers kanskje flyttes etter “patterns”.

The central application is split:

An aggregating agent: -
- myapp/#/temperature
- myapp/#/humidity
Emailing agent -
- myapp/$device-id/altert
Publishes on: -
- myapp/$device-id/command

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MQTT - The protocol - Retained message

Message is kept by the server even after disconnect

CONNECT
PUBLISH -
- RETAIN
- $app/$device/temperature
- 22.3
DISCONNECT

Later on:

SUBSCRIBE -
- $app/#/temperature
PUBLISH -
- $app/$device/temperature
- 22.3

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MQTT - The protocol - Will message

Message sent when you disconnect

Client #1:

CONNECT -
- WILL TOPIC: $app/$device/online
- WILL PAYLOAD: 0
PUBLISH -
- $app/$device/online
- 1
DISCONNECT

Broker

To all subscribers PUBLISH -
- $app/$device/online
- 0

MQTT - Patterns

Må utvides

Explain:

Push vs pull, central applications can push to clients
mostly mqtt, some http
Client id - sparker ut gamle koblinger
Keep alive / ping meldinger
Alternative transporter - websockets(!)

MQTT - Implementations

Mosquitto
Eclipse Paho
RabbitMQ
ActiveMQ

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MQTT Cloud Connectors

Cloud -
- Amazon IoT
- Google Cloud IoT
- Microsoft Azure IoT
- CloudMQTT (at Heroku)
DIY -
- ThingMQ
- HiveMQ

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Assignments

Assignment 1: Blink a led

Assignment 2: Connect to Wi-Fi

Assignment 3: Connect to MQTT broker

Assignment 4: Network play time

Measure round trip time/latency. Measure UDP, TCP. Measure when the packet size is greater than the MTU
Notice variations in RTT

Wikipedia “Internet of Things”↩