Elecrow LoRaWAN Bridge

Turn an Elecrow All-in-One NANO sensor kit into a wireless LoRaWAN weather station with a $4 ESP32-C3 and a $15 REYAX RYLR993 radio module — data flowing into ChirpStack in under an hour.

Architecture

Nano R4 (8 sensors + LCD) ──[UART CSV]──▶ ESP32-C3 ──[UART AT]──▶ RYLR993 ──[LoRa]──▶ ChirpStack

Project Structure

├── nano-firmware/
│   └── elecrow_sensor_bridge.ino     — Arduino Nano R4 sensor firmware
├── rlr993-c3-firmware/
│   ├── main.cpp                       — ESP32-C3 LoRaWAN auto-join firmware
│   └── platformio.ini                 — PlatformIO project config
├── diagrams/
│   ├── architecture.png               — Full system architecture diagram
│   ├── wiring_detail.png              — Wiring diagram
│   └── data-flow.png                  — Data pipeline flow
└── docs/
    └── README-orig.md                 — Original project guide

Firmware Overview

nano-firmware/elecrow_sensor_bridge.ino

• Reads all 8 sensors (AHT20, BH1750, HC-SR04, mic, PIR, soil moisture, pot, accelerometer)
• Drives 16×2 I2C LCD with 8 navigable pages (K1 cycle, K2 freeze, K3 relay toggle)
• Outputs CSV on Serial1 (D1) every 30s at 9600 baud

rlr993-c3-firmware/main.cpp

• Full OTAA join sequence (NWKKEY=APPKEY, BAND=8 for US915)
• Sends CayenneLPP payloads on port 2 every 30s
• LED feedback at every stage (alive → AT OK → JOINED → sending)

⚠️ Key Lessons

1. NWKKEY must equal APPKEY — without it, the module can't decrypt the Join-Accept
2. AT+BAND=8 — the Arduino library maps US915 to band 11 internally; override with BAND=8
3. GPIO20/21 not GPIO4/5 — only GPIO20(RX)/GPIO21(TX) work with the RYLR993 at 9600 baud

⚠️ Hardware

• RYLR993 VDD = 3.0–3.6V max — 5V will destroy it
• NRST → VDD jumper is mandatory (module stays in reset otherwise)
• Disable the servo in firmware (~500mA stall draw) to power ESP32-C3 + RYLR993 from Nano's 5V pin

License

MIT