🎛️ SensorPod

A super-modular IoT sensor node built around the ATmega328, designed for Smart Irrigation / Smart Farming with RS485 communication.

📖 Overview

SensorPod is an affordable, modular Smart Irrigation system optimized for farming operations, particularly in Indonesia. It features 4 capacitive soil moisture sensors connected via RS485 communication protocol, enabling multi-node deployments in distributed IoT networks.

⚙️ Hardware Specifications

Component	Specification
Microcontroller	ATmega328 Pro Mini (3.3V, 8MHz)
Soil Moisture Sensors	4x Capacitive Soil Moisture Sensor V2
Communication	RS485 Protocol (MAX3485)
Power Supply	3-12V input with 3V regulator
UART Baud Rate	9600 baud
Buffer Size	32 bytes

🚀 Core Features

• ✅ 4 Soil Moisture Sensors - Per-sensor calibration to compensate for component tolerance drift
• ✅ RS485 Multi-Node Communication - Connect up to 254 nodes on a single bus
• ✅ Configurable Node IDs - Persistent storage via EEPROM
• ✅ Per-Sensor Calibration - Individual dry/wet point adjustment for each sensor
• ✅ Low Power Design - Sensor power rails toggle on/off for efficiency
• ✅ Non-blocking Async Sampling - 10-sample averaging with outlier rejection
• ✅ Watchdog Timer - 8-second reset protection
• ✅ EEPROM Persistence - Calibration data and node ID stored permanently

📁 Project Structure

🔌 Pin Configuration

Pin	Function	Port
A0	Soil Sensor 1 (Analog Input)	-
A1	Soil Sensor 2 (Analog Input)	-
A2	Soil Sensor 3 (Analog Input)	-
A3	Soil Sensor 4 (Analog Input)	-
2	Soil Power Rail 1-2 (Digital Out)	-
3	Soil Power Rail 3-4 (Digital Out)	-
5	RS485 Enable (Digital Out)	-

📡 Communication Protocol

Command Format

All commands follow the pattern: <PREFIX><NODE_ID>[:<PARAMETERS>]

Available Commands

Read Request

• Format: R<NODE_ID>\r\n
• Example: R2 (Request reading from node 2)
• Response: N2:45,52,38,41 (Node 2, sensors 1-4 moisture percentages)

Calibration Commands

• Enter Calibration: K<NODE_ID>\r\n (Hold both power rails on)
• Set Dry Point: K<NODE_ID>:DRY:<SENSOR_INDEX>\r\n (Store raw ADC value)
• Set Wet Point: K<NODE_ID>:WET:<SENSOR_INDEX>\r\n (Store raw ADC value)
• Set Node ID: K<NODE_ID>:SETID:<NEW_ID>\r\n (Persist new node ID)
• Calibration Info: K<NODE_ID>:INFO\r\n (List calibration status)
• Exit Calibration: Auto-exit after 5 minutes of inactivity

Packet Format

struct SensorPacket {
    uint8_t nodeId;       // 1-254
    uint8_t soil1;        // Moisture % (0-100)
    uint8_t soil2;        // Moisture % (0-100)
    uint8_t soil3;        // Moisture % (0-100)
    uint8_t soil4;        // Moisture % (0-100)
};

# Activate calibration mode on node 2
K2

# Place sensor 1 in dry air and capture raw value
K2:DRY:1
# Board will output raw ADC reading; note it down

# Place sensor 1 in water and capture raw value
K2:WET:1
# Board will output raw ADC reading

# Repeat for sensors 2, 3, 4 as needed