IoT Engineering

Project Example

A temperature and humidity monitoring system with configurable alerts.

Introduction

This project is part of the IoT Engineering course.

• 2-person teams, building an IoT system.
• 32 hours of work per person, 1 prototype.
• 10' presentation of the project at Demo Day.
• Slides, source code and setup steps on GitHub.
• Both team members are able to explain the project.

See use cases and reference model below.

Team members

• @tamberg
• @DIYKulturZH

Deliverables

The following deliverables are mandatory.

Source code

Source code, Arduino C, JS or Python, committed to (this) project repo.

Sensor device

Embedded code / microcontroller firmware.

Source code

• Arduino/nRF52840_DHT11_Test/nRF52840_DHT11_Test.ino
• Arduino/nRF52840_LoRaWAN_Test/nRF52840_LoRaWAN_Test.ino
• Arduino/nRF52840_LoRaWAN_DHT11_Device/nRF52840_LoRaWAN_DHT11_Device.ino

Setup software

• Edit nRF52840_LoRaWAN_DHT11_Device.ino to set TTN NwkSKey, AppSKey and DevAddr:

  static const u1_t PROGMEM NWKSKEY[16] = { 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 };
  static const u1_t PROGMEM APPSKEY[16] = { 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 };
  static const u4_t DEVADDR = 0x00000000;

Setup hardware

• The sensor device consists of a nRF52840, RFM95W, Grove adapter and a DHT11 sensor.
• Stack the nRF52840 on top of the RFM95W on top of the Grove adapter.
• Connect the DHT11 sensor to A4 of the Grove adapter.

Build an enclosure

• See https://www.thingiverse.com/thing:3638252

Actuator device

Embedded code / microcontroller firmware.

Source code

• Arduino/ESP8266_Display_Test/ESP8266_Display_Test.ino
• Arduino/ESP8266_JSON_Test/ESP8266_JSON_Test.ino
• Arduino/ESP8266_MqttSubClient_Test/ESP8266_MqttSubClient_Test.ino
• Arduino/ESP8266_SetAlert_Test/ESP8266_SetAlert_Test.ino
• ...

Setup software

• Set Wi-Fi credentials

  const char *ssid = "MY_SSID";
  const char *password = "MY_PASSWORD";

• Set ThingSpeak keys

  const char *mqttPassword = "TS_MQTT_API_KEY";
  const char *channelId = "TS_CHANNEL_ID";
  const char *readApiKey = "TS_READ_API_KEY";

Setup hardware

• The actuator device consists of a ESP8266, Grove adapter, buzzer (or LED), button, rotary angle sensor, and a display.
• Stack the ESP8266 on top of the Grove adapter.
• Connect the buzzer (or LED) to D2, button to D4, rotary angle sensor to A0, display to I2C_1 of the Grove adapter.

Note: the Grove adapter reset issue does not seem to affect this setup. But programming of the ESP8266 only works, if the Grove adapter is removed.

Build an enclosure

• See https://www.thingiverse.com/thing:3672408

TTN backend

... IoT platform setup steps.

• Register an application named fhnw-project-example
• Register a device named fhnw-project-example-arduino-1
• Get ABP keys, NwkSKey, AppSKey and DevAddr (for nRF52840 setup above)
• See http://www.tamberg.org/fhnw/2019/IoT08LoRaWANConnectivity.pdf p.18, 19 and 21

ThingSpeak dashboard

... IoT platform setup steps.

• Go to http://thingspeak.com
• Create a Channel per TTN device
• Add field1 named Temperature
• Add field2 named Humidity
• Set channel visibility to public (for demo)

TTN to ThingSpeak adapter

Glue Code used on the gateway or "in the cloud".

Source code

• Nodejs/TtnToThingSpeakAdapter/index.js
• Nodejs/TtnToThingSpeakAdapter/now.json

Setup

• Edit index.js to add your TTN AppID:

  const appId = "TTN_APP_ID";

  and per device TTN device IDs and ThingSpeak Write API keys:

  const writeApiKeys = {
      "TTN_DEVICE_ID_1": "WRITE_API_KEY_1", // CHANNEL_ID_1
      ...
  }

• To deploy the code on Zeit Now, type:

  $ cd Nodejs/TtnToThingSpeakAdapter
  $ now

Presentation

4-slide presentation, PDF format, committed to (this) project repo.

• Docs/ProjectExample.pdf

Use cases

Use-case of your project.

This project is a temperature and humidity monitoring system with configurable alerts.

• Measure temperature and humidity ✓
• Display (historic) measurements ✓
• Set a temperature or humidity alert threshold ✓
• Get a temperature or humidity alert
• Confirm an alert

Why? "Cellar is too humid", "Oven is ready", ...

Reference model

Reference model of your project.

Interface documentation

Single slide interface documentation.

• HTTP API to write to ThingSpeak

  $ curl -vX POST https://api.thingspeak.com/update --data 'key=WRITE_API_KEY&field1=23&field2=42'

• MQTT API to read from ThingSpeak

  $ mqtt sub -t 'channels/CHANNEL_ID/subscribe/json/READ_API_KEY' -h 'mqtt.thingspeak.com' -u 'esp8266-CHANNEL_ID' -P 'MQTT_API_KEY' -p 1883 -q 0
  
  {
    "channel_id":0,
    "created_at":"2019-04-22T15:44:18Z",
    "entry_id":2706,
    "field1":"23",
    "field2":"42",
    "latitude":null,
    "longitude":null,
    "elevation":null,
    "status":null
  }

Issues

Issues you faced, how you solved them.

• ESP8266 programming works without adapter only.
• Pin collision, D5 used by both, DHT11 and RFM95W.
• Connecting to ThingSpeak MQTT API, -u, -P, QoS 0.
• Getting the state machine right on actuator device.
• Data drops to 0 on ThingSpeak.
• For details, see issues on GitHub.

Live demo

Working end-to-end prototype, "device to cloud", part of your 10' presentation.

1) Sensor input on a IoT device triggers an event.

• Sensor device

  • Use case: Measure temperature and humidity

• Actuator device

  • Use case: Set a temperature or humidity alert threshold

2) The event or measurement shows up online, in an app or Web client.

• Web browser
  • Use case: Display (historic) measurements
  • https://thingspeak.com/channels/758483

3) The event triggers actuator output on the same or on a separate IoT device.

• Actuator device
  • Use case: Get a temperature or humidity alert
  • Use case: Confirm an alert

Submission deadline

Commit and push to (this) project repo before Demo Day, 03.06.2019, 00:00.