ESP32 Moisture Sensor

ESP32-based soil moisture monitoring system for garden irrigation with temperature compensation and MQTT publishing.

Features

• Multi-sensor support: Up to 4 frequency-based moisture sensors
• Temperature monitoring: DS18B20 sensors on dual OneWire buses (long/short)
• MQTT publishing: Real-time data to MQTT broker
• Temperature compensation: Improves moisture reading accuracy
• Web interface: Real-time monitoring and manual controls
• Non-blocking architecture: State machine approach prevents interface freezing
• Comprehensive diagnostics: OneWire bus troubleshooting and logging

Hardware

Hardware schematics and KiCad project available in separate repository: moisture-sensor-hardware

Key Components

• ESP32 microcontroller
• Frequency-based moisture sensors (up to 4)
• DS18B20 temperature sensors
• Relay control for sensor power management
• WiFi connectivity for MQTT

Pin Configuration

• Moisture sensor relays: GPIO 33, 5, 18, 25
• OneWire buses: GPIO 13 (short), GPIO 14 (long)
• Bus relay control: GPIO 12 (short), GPIO 26 (long)
• Frequency input: GPIO 21
• LED indicator: GPIO 2

Prerequisites

• ESP-IDF: Version 6.0 or later
• Python: 3.8+ (for ESP-IDF tools)
• USB driver: CH340 driver for ESP32 communication (macOS/Windows)

Install ESP-IDF

# Follow official ESP-IDF installation guide
# https://docs.espressif.com/projects/esp-idf/en/latest/esp32/get-started/

# Quick start (macOS/Linux)
mkdir -p ~/esp
cd ~/esp
git clone --recursive https://github.com/espressif/esp-idf.git
cd esp-idf
./install.sh esp32
. ./export.sh

Building and Flashing

Configure Environment

# Load ESP-IDF environment (run in each new terminal session)
. ~/esp/esp-idf/export.sh

Build

# Build the project
idf.py build

# Or use the convenience script (if configured)
./startmeup.sh

Flash to Device

# Flash and monitor
idf.py -p /dev/cu.usbserial-XXXX flash monitor

# Or let it auto-detect the port
idf.py flash monitor

Common Commands

idf.py build              # Build project
idf.py clean              # Clean build files
idf.py menuconfig         # Configure project settings
idf.py size               # Show memory usage
idf.py erase-flash        # Completely erase flash
idf.py build flash monitor # Build, flash, and monitor in one command

Configuration

WiFi and MQTT Settings

Currently hardcoded in source. Edit in main/network.c:

// WiFi credentials
#define WIFI_SSID "your-ssid"
#define WIFI_PASS "your-password"

// MQTT broker
#define MQTT_BROKER "mqtt://your-broker:1883"

Note: Configuration will be moved to NVS storage in future update

Temperature Sensor Configuration

Sensor addresses and names configured in main/MoistureSensor.c. Use diagnostic output to find your sensor addresses:

TempSensorConfig LONG_BUS_SENSORS[] = {
    {0x28, 0xFF, 0x64, 0x0E, 0x8E, 0x90, 0x3C, 0x5E, "Sensor1"},
    // Add your sensors here
};

Architecture

Main Components

• MoistureSensor.c: Main application with sensor reading state machine
• network.c/h: WiFi and MQTT connectivity
• hardware.c/h: Hardware initialization and pin configuration
• temperature_lib.c/h: OneWire temperature sensor handling
• webserver.c/h: Async HTTP server for monitoring
• onewire_custom.c/h: Native ESP-IDF OneWire implementation

Key Functions

• readAndPublishSensorData(): Non-blocking sensor reading with frequency measurement
• readTemperatureBus(): OneWire temperature reading with retry logic
• convertHzToKPa(): Frequency to pressure conversion (Hz → kPa)
• applyTemperatureCompensation(): Temperature compensation for moisture readings

Data Flow

1. Sensor activation: Relay powers sensor, wait for stabilization
2. Frequency measurement: Count pulses over measurement period
3. Temperature reading: Read DS18B20 on appropriate bus
4. Conversion: Hz → kPa with temperature compensation
5. Publishing: Send data via MQTT
6. Web interface: Update real-time display

Web Interface

Access at http://[ESP32_IP_ADDRESS]/ after device connects to WiFi.

Features:

• Real-time sensor readings
• Manual relay control
• Pause/resume measurements
• System diagnostics

Development Status

Current: ✅ Fully converted to native ESP-IDF (no Arduino dependencies)

Recent Changes

• Migrated from Arduino framework to ESP-IDF native APIs
• Removed all Arduino library dependencies
• Implemented native OneWire protocol
• ESP-IDF 6.0 compatible

Troubleshooting

Serial Port Not Detected (macOS)

# Install CH340 driver
brew tap homebrew/cask-drivers
brew install --cask wch-ch34x-usb-serial-driver

# Restart Mac, then check for port
ls /dev/cu.*

Build Errors

# Clean and rebuild
idf.py fullclean
idf.py build

OneWire Sensor Issues

Enable diagnostic logging in temperature_lib.c to troubleshoot sensor detection and reading issues. Check serial monitor output for detailed bus diagnostics.

License

[Specify your license here]

Contributing

Issues and pull requests welcome!

Author

Ian Harris - GitHub