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IoT Workshop

Trygve Laugstøl <trygvis@trygvis.io>

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NodeMCU

NodeMCU hardware

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ESP8266 software layers

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ESP8266 + Arduino

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

Arduino IDE

Arduino code structure

void setup() {
-    // Called once
-}
-
-void loop() {
-    // Called repeatedly
-}

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Arduino file structure

foo/
-  foo.ino
-  config.h

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Generic Arduino APIs

// Pin: D0, D1, etc.
-// Mode: OUTPUT, INPUT, INPUT_PULLUP
-void pinMode(uint8_t pin, uint8_t mode);
-
-// State: HIGH, LOW, true/false, 1/0
-void digitalWrite(uint8_t pin, uint8_t state);
-int digitalRead(uint8_t pin);
-
-unsigned long now millis();
-unsigned long now micros();

ESP Arduino APIs

class {
-    void restart();
-    uint32_t getFreeHeap();
-    uint32_t getChipId();
-
-    ...
-} ESP;
-
-// Usage
-ESP.restart();

ESP Arduino APIs

class {
-    String macAddress();
-
-    wl_status_t status();
-    int32_t RSSI();
-
-    IPAddress localIP();
-    IPAddress subnetMask();
-    IPAddress gatewayIP();
-    IPAddress dnsIP(uint8_t dns_no = 0);
-
-    ...
-} WiFi;
-
-// Usage:
-
-Serial.println(WiFi.localIP().toString());

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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
Has connectivity -
- Bluetooth
- Wi-Fi
- NB-IoT
- LTE Cat-M
- LoRA
- Proprietary radio

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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

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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

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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

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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

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Going back to basics

What is the internet again?

TCP/IP Layers

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Packet encapsulation

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Network interface

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

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Internet

IP
ICMP

Transport

TCP
UDP
SCTP
QUIC

Layer 7: Application Layer

HTTP
DNS
MQTT
CoAP
(everything else..)

Details: IP Header

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Details: UDP Header

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Lecture: MQTT

MQTT

Message Queuing Telemetry Transport
Wikipedia: MQTT

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Device and application architecture with MQTT

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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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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 Packet

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

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MQTT Connect

CONNECT -
- clientId
- username
- password
- keepAlive

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Keep alive -
- PINGREQ
- PINGRESP

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

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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 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 on Arduino

PubSubClient is our MQTT client implementation.

WiFiClient wifiClient;
-PubSubClient mqtt(wifiClient);
-
-void callback(char* topic,
-              byte* payload,
-              unsigned int length);
-
-void setup() {
-    // Configure WiFi
-    mqtt.setServer(mqtt_server, 1883);
-    mqtt.setCallback(callback);
-}

MQTT on Arduino

void loop() {
-    if (!mqtt.connected())
-        reconnect();
-    else
-        mqtt.loop();
-    // Do work
-}
-
-void reconnect() {
-    while (!mqtt.connect(client_id));
-
-    mqtt.subscribe(topic_pattern);
-}

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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 topic architecture

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MQTT topic architecture

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MQTT - Patterns

Combining MQTT and HTTP
Using web sockets transport

Assignment

mqtt2

Assignment

mqtt3

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Wikipedia “Internet of Things”↩