ESP-NOW UART Hub

A bridge component that receives sensor data via ESP-NOW wireless protocol and forwards it to an MQTT hub via UART communication. This is part of the FAO56 IoT system for agricultural monitoring.

Overview

The ESP-NOW UART Hub acts as an intermediary between wireless sensor nodes and the main MQTT hub. It receives sensor data from multiple ESP-NOW enabled sensor nodes and relays this data through a UART connection to the MQTT hub for further processing and cloud transmission.

Architecture

[Sensor Nodes] ---> [ESP-NOW UART Hub] ---> [UART] ---> [MQTT Hub] ---> [Cloud/Broker]
    (Wireless)           (This Device)      (Serial)     (WiFi/MQTT)

Features

• ESP-NOW Communication: Receives data from multiple sensor nodes wirelessly
• Automatic Pairing: Handles pairing requests from new sensor nodes
• UART Bridge: Forwards sensor data to MQTT hub via serial communication
• WiFi Credential Management: Receives and applies WiFi credentials from MQTT hub
• FreeRTOS Multitasking: Concurrent handling of ESP-NOW and UART communication
• Queue-based Data Handling: Reliable data buffering and transmission

Hardware Requirements

• ESP32 development board (NodeMCU-32S or similar)
• UART connection to MQTT hub device
• Power supply (3.3V or 5V depending on board)

Pin Configuration

#define RX_HUB 26    // UART RX pin for MQTT hub communication
#define TX_HUB 27    // UART TX pin for MQTT hub communication
#define BAUD_RATE 115200

Data Structures

Sensor Data

struct sensorData {
    uint8_t msgType;    // Message type (DATA or PAIRING)
    char nodeID[8];     // Sensor node identifier
    float temp;         // Temperature reading
    float humidity;     // Humidity reading
    long moisture;      // Soil moisture reading
};

Pairing Structure

struct structPairing {
    uint8_t msgType;    // PAIRING message type
    char nodeID[8];     // Node identifier
    uint8_t macAddr[6]; // MAC address
    uint8_t channel;    // WiFi channel
};

Operation Flow

1. Initialization: Sets up ESP-NOW, UART communication, and FreeRTOS tasks
2. WiFi Setup: Receives WiFi credentials from MQTT hub and connects to network
3. Pairing Process: Handles pairing requests from sensor nodes automatically
4. Data Reception: Receives sensor data from paired nodes via ESP-NOW
5. Data Forwarding: Queues and transmits data to MQTT hub via UART

Tasks

Main Tasks

• startConnection: Handles WiFi connection and ESP-NOW initialization
• sendSerial: Processes queued sensor data and sends to MQTT hub
• handleUartCommands: Processes commands from MQTT hub

Communication Protocol

With Sensor Nodes (ESP-NOW)

• Receives pairing requests and sensor data
• Responds to pairing with hub MAC address and channel
• Maintains peer connections for data reception

With MQTT Hub (UART)

• Receives WiFi credentials (marked with '`')
• Responds to test connections (T -> A)
• Forwards sensor data as binary structs
• Confirms WiFi credential receipt with 'W'

Building and Deployment

Prerequisites

• PlatformIO IDE or Arduino IDE with ESP32 support
• ESP32 board package installed

Build Configuration

The project uses PlatformIO with configuration in platformio.ini:

• Target: ESP32 NodeMCU-32S
• Framework: Arduino
• Monitor speed: 115200 baud

Upload

1. Connect ESP32 to computer via USB
2. Select correct COM port
3. Build and upload firmware
4. Monitor serial output for debugging

Configuration

The config file is located in include/config.h

Hub ID

Default hub identifier is set in config.h:

#define HUB_ID "H-0"

UART Pins

Modify pin assignments in config.h if needed:

#define RX_HUB 26
#define TX_HUB 27

Debugging

The system provides extensive serial debugging output:

• ESP-NOW initialization status
• Pairing process details
• Data reception and forwarding
• WiFi connection status
• UART communication logs

Monitor at 115200 baud to view debug information.

Integration

This hub works in conjunction with:

• Sensor Nodes: ESP32-based devices running the fao56-sensor-node firmware
• MQTT Hub: The fao56-uart-mqtt-hub for cloud connectivity

Troubleshooting

Common Issues

1. No sensor data received: Check ESP-NOW pairing and channel settings
2. UART communication failed: Verify pin connections and baud rate
3. WiFi connection issues: Ensure credentials are properly received from MQTT hub
4. Memory issues: Monitor task stack sizes and queue lengths

LED Indicators

• Built-in LED activity indicates various operational states
• Check serial monitor for detailed status information

License

Part of the FAO56 IoT agricultural monitoring system.