Repository Overview

This project contains firmware for two types of nodes based on Arduino/ESP32 and LoRa:

• master-node: Listens for LoRa packets from sensor nodes, filters messages addressed to "master-node", and processes the payloads (e.g., prints to serial, forwards to a backend, etc.).
• station-node: Reads temperature and humidity from a DHT22 sensor and ambient light via a photoresistor, packages the data into a JSON payload with a "to":"master-node" field, and sends it over LoRa.

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Repository Structure

├── master-node/
│   └── master-node.ino      # Master node firmware
├── station-node/
│   └── station-node.ino     # Station (sensor) node firmware
├── README.md                # This guide (English version)
└── doc/                     # Flow diagram images (.jpg)

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Prerequisites

• Development Environment:
  • Arduino IDE (>= 1.8.13) or PlatformIO
• Arduino Libraries:
  • LoRa by Sandeep Mistry
  • DHT sensor library by Adafruit
  • SPI (bundled with Arduino)
• Hardware:
  • 2× Arduino or ESP32-based boards (3.3 V compatible)
  • 2× LoRa SX1276/78 radio modules
  • 1× DHT22 temperature & humidity sensor
  • 1× Photoresistor (LDR)
  • Jumper wires and power supply

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Hardware Setup

master-node

LoRa Module Pin	Board Pin
NSS (CS)	10
RESET	9
DIO0	2
SPI SCK	13
SPI MOSI	11
SPI MISO	12
3.3 V	3.3 V
GND	GND

station-node

Component	Pin
DHT22 DATA	2
DHT22 VCC	5 V
DHT22 GND	GND
LDR Divider	A0
LoRa NSS (CS)	18
LoRa RESET	14
LoRa DIO0	26
SPI SCK	5
SPI MOSI	27
SPI MISO	19

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Software Setup

1. Clone the repository:

    git clone https://github.com/grimimirg/gartner-nodes.git

2. Install libraries in Arduino IDE:
   • Sketch > Include Library > Manage Libraries...
   • Search for and install LoRa and DHT sensor library (Adafruit).
3. Open sketches:
   • master-node/master-node.ino
   • station-node/station-node.ino

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Build & Upload

master-node

1. Select the correct board type (e.g., Arduino Uno or ESP32 Dev Module).
2. Select the COM port.
3. Upload master-node.ino.

station-node

1. Select the correct board type.
2. Select the COM port.
3. Upload station-node.ino.

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Interactions between Station-Node and Master-Node

1. Station-Node wakes up and reads sensors:
   • Temperature and humidity from DHT22.
   • Raw analog light level from LDR, converted to percentage.
2. Payload construction:

   {
     "to": "master-node",
     "temperature": 24.30,
     "humidity": 60.00,
     "lightPercent": 45.20
   }

3. LoRa transmission at 868 MHz in broadcast mode.
4. Master-Node continuously listens for packets:
   • Calls LoRa.parsePacket() to detect incoming data.
   • Reads full payload as string.
   • Checks the "to" field: if it matches "master-node", the packet is accepted.
   • Extracts sensor values and processes them (e.g., prints to serial, logs to SD card, or forwards via a backend).
5. Optional Acknowledgment: You may extend the protocol so that the master-node replies with an ACK packet containing e.g. { "ack": true, "id": "station-1" }.

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Operation

• Station-Node executes every minute (configurable): reads sensors, builds JSON payload, sends via LoRa, then sleeps or delays.
• Master-Node runs in a loop: filters incoming messages, processes valid ones, and ignores others.

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Flow Diagrams

Master Node Flow

Station Node Flow

Master Node Flow

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Customizations

• Frequency: change LORA_FREQ to 433E6 for the EU band. (916 for US)
• Send interval: modify the delay(60000) in station-node.
• Payload format: switch to CSV, binary, or a more compact JSON as needed.

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Debug & Troubleshooting

• Verify SPI wiring and 3.3 V power to LoRa modules.
• Use the Serial Monitor at 115200 baud for debug prints.
• Measure RSSI on the master-node:

  int rssi = LoRa.packetRssi();
  Serial.print("RSSI: "); Serial.println(rssi);

• Ensure both nodes use the same frequency and spreading factor settings.

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License

This project is released under the MIT License.