SmartStore Ecosystem

An automated, IoT-based retail solution engineered with ESP32 nodes, Azure IoT Hub, and FreeRTOS. This project synchronizes real-time weight-based inventory tracking with an automated checkout kiosk.

Overview

The SmartStore Ecosystem consists of two specialized embedded nodes communicating via the cloud to eliminate manual scanning and streamline the shopping experience.

• Inventory Node: Monitors shelf stock in real-time using load cells and sends telemetry to Azure.
• PayDesk Node: Receives the "virtual basket" from the cloud and manages the automated checkout process.

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Key Features

• Real-Time Inventory: Weight-based sensing with ±1g precision using HX711.
• Event-Driven Telemetry: Data is sent to the cloud only when stock changes to optimize power and bandwidth.
• Multitasking Architecture: Built on FreeRTOS to handle sensor sampling and cloud communication concurrently.
• Cloud Synchronization: Secure D2C (Device-to-Cloud) and C2D (Cloud-to-Device) messaging via Azure IoT Hub and MQTT.
• User Interface: Live basket updates on a 2.8" TFT display (ILI9341).

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System Architecture

1. Sensing: Load cells on the shelf detect when a product is removed.
2. Processing: The Inventory ESP32 calculates the item count based on predefined unit weights.
3. Communication: The count is sent as telemetry to Azure IoT Hub.
4. Action: The PayDesk ESP32 receives the message, updates the display, and waits for the user to "Pay" (physical button trigger).

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Hardware Configuration

1. Inventory Node (ESP32)

Component	Data Pin (DT)	Clock Pin (SCK)	Unit Weight (GR)	Product Name
Load Cell 1	GPIO 23	GPIO 22	500g	Dorna
Load Cell 2	GPIO 21	GPIO 19	500g	Coca Cola
Load Cell 3	GPIO 18	GPIO 5	1000g	Doritos
Load Cell 4	GPIO 17	GPIO 16	1500g	Kinder

2. PayDesk Node (ESP32 + TFT)

Component	Pin	Function
TFT CS	GPIO 5	Chip Select (SPI)
TFT DC	GPIO 16	Data/Command
TFT RST	GPIO 4	Reset
Button	GPIO 17	Payment Confirmation
SPI MOSI	GPIO 23	Master Out Slave In
SPI SCK	GPIO 18	Serial Clock

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Firmware Logic

The firmware utilizes FreeRTOS tasks to ensure high responsiveness:

Inventory Tasks:

• inventoryTask: Handles high-frequency sampling of the load cells and data filtering.
• device_to_cloud: Manages the MQTT connection and pushes updates to Azure when a change is detected.

PayDesk Tasks:

• get_virtual_basket: Listens for C2D messages and parses the incoming product strings.
• pay_desk: Monitors the hardware interrupt/button for transaction finalization.

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Tech Stack

• Language: C/C++ (Arduino Framework)
• RTOS: FreeRTOS
• Cloud: Azure IoT Hub
• Protocol: MQTT over TLS
• Libraries:
  • HX711 (Load cell amplifier)
  • Adafruit_ILI9341 & Adafruit_GFX (Display)
  • PubSubClient (Messaging)
  • mbedtls (Encryption)

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Setup & Installation

1. Azure Configuration:
   • Create an IoT Hub and register two devices.
   • Generate SAS tokens or X.509 certificates for authentication.
2. Library Installation:
   • Install HX711, Adafruit ILI9341, and AzureIoTHub libraries via PlatformIO or Arduino Library Manager.
3. Calibration:
   • Adjust the SCALE constant in the Inventory code to match your specific load cell calibration factor.
4. Deployment:
   • Flash the Inventory code to the shelf ESP32.
   • Flash the PayDesk code to the checkout ESP32.

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Author

[raylaj23] Computer Engineering Student | IoT Enthusiast