BlackBox - IoT RTOS Shipment Monitor

Overview

This project is an IoT-based smart shipment monitoring system built using FreeRTOS. It utilizes a dual-microcontroller architecture with an NXP MCXC444 MCU handling real-time hardware interrupts and physical indicators, and an ESP32 handling environmental sensors, geolocation, and cloud synchronization via Firebase Realtime Database. A Django web backend acts as a dashboard for tracking shipment metrics and configuring run thresholds.

Hardware Components

NXP MCXC444 (FRDM Board)

• Sensors: Hall Effect Sensor (detects box open/close), Shock Sensor.
• Actuators & Indicators:
  • RGB LED (State indication: Blue = Idle, Green = Active Run, Red = Box Opened).
  • Active Buzzer (Sounds an alarm when the box is opened during a run).
  • 4-Digit SLCD (Cycles through Shocks, Opens, and Environmental Threshold Exceeded counts).
• Inputs: SW2 Button (Manual counter reset).

ESP32

• Sensors: DHT11 (Temperature & Humidity), LDR / Photoresistor (Light Level).
• Connectivity: Wi-Fi module connecting to Firebase RTDB and an external IP Geolocation API (ip-api.com).

Software Architecture

The system uses FreeRTOS on both microcontrollers to handle concurrent tasks safely and efficiently.

NXP MCXC444 RTOS Tasks

• shockTask / hallTask: Responds to hardware interrupts (via binary semaphores) to increment shock counters and detect box state changes.
• indicatorTask: Controls the RGB LED based on the current system and shipment state.
• buzzerTask: Manages the active buzzer alert when a box is opened during an active shipment run.
• lcdTask: Periodically cycles the SLCD display to show runtime statistics (Shocks, Opens, Temp/Humidity/Light exceeded counts).
• recvTask: Parses UART messages from the ESP32 (Run status, environmental alerts).
• resetTask: Monitors the SW2 button for manual resetting of the local system state.

ESP32 RTOS Tasks

• TaskTempHumid & TaskPhotoresistor: Periodically samples DHT11 and LDR sensors, comparing them against cloud-configured thresholds. Sends environmental alerts over UART to the MCXC444 if thresholds are exceeded.
• TaskGeoLocation: Fetches the shipment's latitude and longitude via IP-based geolocation every 5 minutes.
• TaskReceiveFromMCXC444: Listens for UART payloads from the MCXC444 regarding shock events and box state changes.
• TaskFirebase: Handles two-way synchronization with Firebase Realtime Database:
  • Polling: Checks /Active_Run status and /run_config/ (thresholds) periodically.
  • Pushing: Uploads telemetry (temperature, humidity, light, geolocation, shocks, opens, status) to /shipment_logs every 30 seconds when a run is active.
• TaskWiFiManager: Ensures persistent Wi-Fi connectivity and handles auto-reconnection or rebooting if the connection is lost.

Communication Protocol

The microcontrollers communicate over a UART interface (9600 Baud).

• MCXC444 -> ESP32:
  • SHOCK:<count>, BOX_OPEN:<count>, BOX_CLOSED
• ESP32 -> MCXC444:
  • RUN:<1/0> (Run state synced from cloud)
  • TEXC:<count>, HEXC:<count>, LEXC:<count> (Threshold exceeded alerts)
  • TEMP:<f>,HUMI:<f>, LIGHT:<val> (Informational environmental metrics)

Cloud Integration

• Firebase Realtime Database: Acts as the central data broker, maintaining run configurations (temperature, humidity, and light thresholds), the active run toggle, and a historical log of telemetry data.
• Django Backend: Interfaces with Firebase to present a real-time tracking dashboard, allowing users to start/stop shipment runs, visualize environmental data, and receive real-time alerts.