IoT Workshop

Trygve Laugstøl <trygvis@trygvis.io>

What is IoT

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?

What is an IoT Device?

  • Constrained in (one or more of):
    • Memory
    • CPU
    • Network bandwidth and/or latency
    • Storage
  • Has connectivity
    • Bluetooth
    • Wi-Fi
    • NB-IoT
    • LTE Cat-M
    • LoRA
    • Proprietary radio

IoT Devices - Bluetooth 4/5 chips

Chip CPU Freq RAM Flash Price
nRF52810 Cortex-M4 64 MHz 24k 192k $1.88
nRF52832 Cortex-M4F 32k 256k $2.54
64k 512k $2.59
nRF52840 Cortex-M4F 256k 1024k $3.85
  • nRF52810: High performance, entry-level Bluetooth 4/ANT/2.4GHz SoC
  • nRF52832: High performance Bluetooth 4/ANT/2.4GHz SoC
  • nRF52840: Advanced multi-protocol System-on-Chip Supporting: Bluetooth 5, ANT/ANT+, 802.15.4 and 2.4GHz proprietary

IoT Devices - LoRA

Modules

Module Data Rate Price
RN2483A-I/RM104 $12.05 @ 250
CMWX1ZZABZ-078 SX1276 $10.74 @ 1000
RF-LORA-868-SO SX1272 $16.55 @ 1000

Chips

Chip Price
SX1281 $3.23
SX1272 $4.25
SX1276 $4.25
SX1279 $4.74

IoT Devices - NB-IoT

Module Price
uBlox SARA-N210 ~$10 @ 100
Sierra Wireless HL7800_1103933 $15.72

IoT Devices - Wi-Fi

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

ESP8266 details - Power usage

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

Going back to basics

What is the internet again?

OSI model

  1. Physical Layer
  2. Data Link Layer
  3. Network Layer
  4. Transport Layer
  5. Session Layer
  6. Presentation Layer
  7. Application Layer

Layer 1: Physical Layer

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

Layer 3: Network Layer

  • IP
  • ICMP
  • IPX

Layer 4: Transport Layer

  • TCP
  • UDP

Layer 5: Session Layer

  • “sockets”
  • NetBIOS

Layer 6: Presentation Layer

  • SSL

Layer 7: Application Layer

  • HTTP
  • DNS
  • MQTT
  • CoAP
  • (everything else..)

Details: IP

Details: UDP

TODO: add payload to “ip packets”

Lecture: ESP8266

NodeMCU hardware

NodeMCU hardware

ESP8266 software layers

ESP8266 + Arduino

  • Standard Arduino IDE
  • ESP8266 Arduino core
    • https://github.com/esp8266/Arduino

Arduino IDE

Arduino code structure

Arduino file structure

foo/
  foo.ino
  config.h

Generic Arduino APIs

ESP Arduino APIs

ESP Arduino APIs

Lecture: MQTT

MQTT

MQTT - Implementations

  • Mosquitto
  • Eclipse Paho
  • RabbitMQ
  • ActiveMQ

MQTT Cloud Connectors

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

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

MQTT - The protocol - MQTT Packet

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

MQTT - The protocol - Keep alive

TODO

MQTT - The protocol - MQTT Topic

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

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

MQTT - The protocol - Will message

Message sent when you disconnect

Client #1:

  1. CONNECT
    • WILL TOPIC: $app/$device/online
    • WILL PAYLOAD: 0
  2. PUBLISH
    • $app/$device/online
    • 1
  3. DISCONNECT

Broker

  1. To all subscribers PUBLISH
    • $app/$device/online
    • 0

MQTT - The protocol - Client id

TODO

Device and application architecture with MQTT

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

MQTT on Arduino

PubSubClient is our MQTT client implementation.

MQTT on Arduino

Assignment

  • mqtt

MQTT topic architecture

The central application is split:

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

MQTT - Patterns

  • Combining MQTT and HTTP
  • Using web sockets transport

Assignment

  • mqtt2

Assignment

  • mqtt3

  1. Wikipedia “Internet of Things”