mgrub / demo_sensor_network

demonstration of a sensor network with actual hardware

Sensor Network Demonstrator

This is the repository for a small sensor network demonstrator. It can be used to demonstrate various aspects of the IoT like edge device/fog/cloud devices, data streams, sensor self-description, homogeneous/heterogeneous networks, absolute time synchronization and wireless sensor networks. To do so, it builds on existing standards (WIFI, MQTT, NTP, GPS, JSON) and uses off-the-shelf hardware.

The repository documents:

• hardware setup
• communication setup
• Arduino microcontroller code
• Arduino programming environment
• RaspberryPi setup

Hardware Setup

• 3x Arduino Nano 33 IoT
• 1x RaspberryPi 4
• 1x Waveshare NEO-M8T GNSS TIMING HAT
• power supply and mount for the Arduinos
• power supply, case and fan for the RaspberryPi
• 1x development PC

Communication Setup

┌───────────┐  ┌───────────┐  ┌───────────┐
│ Arduino 1 │  │ Arduino 2 │  │ Arduino 3 │
│           │  │           │  │           │
│   - Wifi  │  │   - Wifi  │  │   - Wifi  │
└────┬──────┘  └────┬──────┘  └────┬──────┘
     │ ▲            │ ▲            │ ▲
 MQTT│ │        MQTT│ │        MQTT│ │
     │ │NTP         │ │NTP         │ │NTP
     ▼ │            ▼ │            ▼ │
┌──────┴──────────────┴──────────────┴────┐
│ Raspberry Pi                            │
│                                         │  Serial    ┌─────────────────┐
│   - Wifi Accesspoint                    │◄───────────┤ GNSS satellites │
│   - MQTT Broker                         │  Interface └─────────────────┘
│   - NTP Server                          │
└─────────┬───────────────────────────────┘
          │                 ▲
          │                 │
      MQTT│             MQTT│
          │                 │
          ▼                 ▼
      ┌───────┐     ┌────────────────┐
      │ Users │     │ Cloud-Services │
      └───────┘     └────────────────┘

MQTT topics

• each Arduino publishes to multiple MQTT topics
  • <sensor_name>/data -> json
  • <sensor_name>/description -> json

Useful Resources

• MQTT Visualizer: http://mqtt-explorer.com/

• MQTT Broker: https://mosquitto.org/download/

• MQTT Docs: https://docs.arduino.cc/tutorials/uno-wifi-rev2/uno-wifi-r2-mqtt-device-to-device

• MQTT Tutorial: https://community.element14.com/challenges-projects/design-challenges/design-for-a-cause-2021/b/blog/posts/connecting-the-arduino-nano-33-iot-with-local-mqtt-broker-2

• Acceleration Sensor Docs: https://www.st.com/resource/en/datasheet/lsm6ds3tr-c.pdf (page 36 -> FIFO mode)

• SparkFun Acceleration Sensor Library: https://github.com/sparkfun/SparkFun_LSM6DS3_Arduino_Library

• NTP Library: https://www.arduino.cc/reference/en/libraries/ntpclient/

• Adhoc Wifi: https://www.elektronik-kompendium.de/sites/raspberry-pi/2002171.htm

• GPS USB NTP: https://klenzel.de/4182

• GPS receiver doc: https://www.waveshare.com/wiki/NEO-M8T_GNSS_TIMING_HAT

Security Setup

Network Level

Wifi connections from and to the RaspberryPi / MQTT Broker are encrypted using WPA2. Thi effectively blocks attackers that do not have the Wifi credentials.

Network level security could be increased further by whitelisting (MAC-addresses of) allowed devices.

Transport Level

A username and password is required to read and write topics from the MQTT broker. However, the message transport itself is not encrypted.

To enable transport encryption a TLS/SSL certificate needs to be issued for the MQTT broker.

Application Level

The payload of the MQTT message is a non-encrypted JSON-string.

TODO / Future Ideas

• MQTT agent for AgentMet4FoF -> check out https://github.com/PTB-M4D/thementag-demo
• test high sampling rates (500-1000 Hz)
• adjust messages sent by Arduino (e.g. follow BMBF FAMOUS approach of eclipse unide)
• adjust self-description message (to something more semantic like JSON-RDF-triples, currently only {"id": "sensor_1"})
• include uncertainty service to add uncertainty based on self-description