LoRa Node (Sensor Transmitter)

Reference README for a LoRa sensor/transmitter node designed to work with the companion gateway repo lora-gateway. It sends compact LoRa frames that the gateway parses and relays to MQTT.

This document is intended to live in the separate Node repository: https://github.com/diegohat/lora-node

Gateway repository for reference: https://github.com/diegohat/lora-gateway

Hardware

• MCU + LoRa radio used in this repo:
  • Arduino Uno + SX1276/SX1278 module
• Antenna matching your regional frequency
• Sensors (examples used in code):
  • Soil hygrometer (digital DO + analog AO)
  • Tilt sensor (digital)

Pinout and Wiring (Arduino Uno)

• LoRa pins (as used in src/main.cpp):
  • SS 10, RST 9, DIO0 2
• Sensors:
  • Hygrometer DO → D3, AO → A0
  • Tilt sensor → D4

Message Format

The gateway expects a one-byte address followed by a UTF-8 text payload containing fields in Portuguese separated by commas:

• First byte: destination address (use the gateway myAddress or 0xFF for broadcast)
• Text payload example produced by this node:
  • Solo=SECO,Umidade=73.00%,Inclinacao=NORMAL

Fields parsed by the gateway and forwarded to MQTT JSON:

• Solo: soil condition
• Umidade: soil moisture (may include % symbol)
• Inclinacao: tilt state

Tip: Keep payloads short to reduce airtime and collisions.

LoRa Settings (must match gateway)

• Frequency: default 915E6 (change per region: 433/868/915 MHz)
• Spreading Factor: SF12
• Coding Rate: 4/8

To interoperate, the node must use identical frequency/SF/CR (and ideally bandwidth) as the gateway.

Example (minimal Arduino snippet)

byte dest = 0x01; // or 0xFF for broadcast
String payload = "Solo=123,Umidade=45%,Inclinacao=2";

LoRa.beginPacket();
LoRa.write(dest);         // address byte first
LoRa.print(payload);      // text payload
LoRa.endPacket();

Power & Duty Cycle

• Respect regional regulations (e.g., duty-cycle, maximum EIRP)
• Use sleep modes to extend battery life (this repo uses rocketscream/Low-Power to sleep ~15 minutes between transmissions)

PlatformIO

This repo includes a PlatformIO configuration for Arduino Uno:

[env:uno]
platform = atmelavr
board = uno
framework = arduino
monitor_speed = 9600

lib_deps =
  sandeepmistry/LoRa
  rocketscream/Low-Power

Build, Upload, Monitor (macOS/zsh)

pio run
pio run -t upload
pio device monitor -b 9600

Ensure wiring matches the pins above and your antenna is connected before powering.

Testing

• With the gateway running, send a packet and watch the gateway serial monitor and MQTT topic (default diegohat/lora).
• Verify that JSON arrives with solo, umidade, inclinacao, rssi, and snr.

Adapting Fields

If your sensor names differ, either:

• Update the node to send Solo, Umidade, and Inclinacao, or
• Modify the gateway parser in lora-gateway/src/main.cpp to match your field names.

Repository Pairing

• Gateway repo: firmware receives LoRa and publishes to MQTT over TLS
• Node repo: this transmitter (sends address byte + text payload)

Keep both READMEs aligned so team members can configure frequency, addressing, and formats consistently.