Wireless Communication - kobeylake/ares-red GitHub Wiki

The system operates on a star topology with the Base Node (nRF52840DK) acting as the central coordinator. Communication is as follows:

• Mobile Node (Thingy:52): Acts as the environmental sensor source, periodically broadcasting data (Co2, temperature, humidity) via BLE advertising.

• Base Node (nRF52840-DK): Scans for mobile node advertisements, calculates a control servo angle, and rebroadcasts a JSON-formatted packet containing all sensor data and angle over BLE advertising. It is also connected via USB UART to a PC running a shell interface for debugging and configuration.

• Actuator Node (nRF52840DK + CRICKIT): Receives JSON packets via BLE, decodes the data, updates the vent angle via a PWM-controlled servo, and forwards the JSON data over UART to a Windows PC for MQTT publishing.

• PC's 1-3 (Grafana + InfluxDB + Mosquitto Broker): Connected to the Actuator Node via UART. Runs Python scripts that read UART data and publish to MQTT, allowing real-time visualisation and logging in Grafana.

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The project uses Bluetooth Low Energy (BLE) in advertising-based mode, along with UART serial and MQTT over TCP/IP, to support multi-node data flow, actuation, and real-time visualisation. The system is distributed across three PCs, each with a dedicated role.

Direction	Source → Destination	Mode	Purpose
Thingy:52 → Base Node	BLE Advertising	Broadcast sensor data	Periodic broadcast of temperature, humidity, and CO₂
Base Node → Actuator Node	BLE Advertising (JSON)	Sensor + angle payload	Transmit fused sensor data and servo angle
Actuator Node → PC 1	UART Serial	JSON to PC	Forward JSON packets over serial to MQTT publisher
PC 1 → PC 3 (Viewer/Grafana)	MQTT over TCP/IP	Broker communication	Visualise real-time sensor and actuator data
PC 2 → Base Node	UART CLI	Shell commands	Control ultrasonic, servo mode, and sensor overrides

• Role: BLE Broadcaster
• Function: Periodically advertises:
  • Temperature
  • Humidity
  • CO₂ (eCO₂/TVOC)
• Communication: BLE Advertising
• Sensor Interface: I²C

• Role: BLE Scanner + Broadcaster
• Functions:
  • Scans BLE packets from Thingy:52
  • Performs sensor fusion to compute servo angle
  • Broadcasts JSON including:
    • Temp, Humidity, CO₂
    • Ultrasonic distance
    • Computed angle
• Communication:
  • BLE Advertising (to Actuator Node)
  • UART CLI for real-time control from PC 2

• Role: BLE Scanner
• Functions:
  • Parses BLE advertisements from Base Node
  • Controls servo via PWM using received angle
  • Sends JSON over UART to PC
• Communication:
  • BLE (input from Base Node)
  • UART (output to PC 1)

• Role: MQTT Bridge
• Functions:
  • Reads JSON from Actuator Node over UART
  • Publishes data to local Mosquitto MQTT broker
• Tools: Python (Paho MQTT), Mosquitto
• Communication:
  • UART (inbound from Actuator Node)
  • MQTT (outbound to PC 3)

• Role: Manual Control Interface
• Functions:
  • Sends control commands to Base Node via Zephyr Shell:
    • ultrasonic_on, ultrasonic_off
    • servo_mode auto/manual
    • sensor_override <CO2> <TEMP>
• Communication: UART Shell

• Role: Real-time Visualisation
• Functions:
  • Subscribes to MQTT broker
  • Visualises sensor data and control state
  • May optionally display local alerts
• Communication: MQTT over Wi-Fi

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