PrecursorLoRa

Precursor LoRa Expansion Module

A production-ready LoRa radio expansion module for the Precursor open-source secure computing platform.

Overview

This module adds LoRaWAN connectivity to the Precursor device, enabling 15km+ range communication without WiFi/Bluetooth attack surface. It fits in the Precursor's battery compartment and connects via the internal GPIO header.

Features

• RAK3172 LoRaWAN Module - Based on STM32WLE5CC with integrated LoRa radio
• Frequency Bands - EU868, US915, AU915, AS923, and more
• Long Range - 15km+ line-of-sight with proper antenna
• Low Power - <2µA sleep current, ideal for battery operation
• Simple Interface - UART AT command interface to Precursor FPGA
• Compact Design - Fits in Precursor battery compartment (50x30mm)

Specifications

Pin Connections

Bill of Materials

Directory Structure

PrecursorLoRa/
├── README.md                 # This file
├── hardware/
│   ├── precursor-lora.kicad_pro    # KiCad 8 project
│   ├── precursor-lora.kicad_sch    # Schematic
│   ├── precursor-lora.kicad_pcb    # PCB layout
│   ├── symbols/                    # Custom symbols
│   └── footprints.pretty/          # Custom footprints
├── fabrication/
│   ├── gerbers/                    # Gerber files for manufacturing
│   ├── bom/                        # Bill of Materials
│   └── pick-and-place/             # Assembly positions
├── docs/
│   └── assembly-notes.md           # Assembly instructions
└── datasheets/                     # Component datasheets (not tracked)

Manufacturing

This board is designed for the NextPCB Accelerator free prototype program.

Design Rules (NextPCB Compatible)

• Minimum trace width: 0.2mm
• Minimum trace spacing: 0.2mm
• Minimum via drill: 0.3mm
• Minimum via pad: 0.6mm
• PCB thickness: 1.6mm
• Copper weight: 1oz
• Surface finish: HASL or ENIG

Generating Gerbers

1. Open hardware/precursor-lora.kicad_pcb in KiCad 8
2. File → Plot → Select Gerber output
3. Include layers: F.Cu, B.Cu, F.Paste, B.Paste, F.SilkS, B.SilkS, F.Mask, B.Mask, Edge.Cuts
4. Generate drill files (Excellon format)
5. Zip all files for upload

Assembly Notes

See docs/assembly-notes.md for detailed assembly instructions.

Key points:

• RAK3172 module has orientation marking (pin 1 dot)
• Apply flux for castellated pad soldering
• Keep RF trace short and over ground plane
• Test continuity before powering

Usage with Precursor

The module communicates via UART AT commands. Example initialization:

AT+NWM=1              # Set LoRaWAN mode
AT+NJM=1              # Set OTAA join mode
AT+DEVEUI=<your_eui>  # Set device EUI
AT+APPEUI=<app_eui>   # Set application EUI
AT+APPKEY=<app_key>   # Set application key
AT+JOIN              # Join network
AT+SEND=1:<data>     # Send data on port 1

License

This project is licensed under CERN-OHL-P v2 (CERN Open Hardware Licence Version 2 - Permissive).

You are free to use, modify, and distribute this design for any purpose.

Resources

• RAK3172 Datasheet
• Precursor Hardware
• AP2112K Datasheet
• NextPCB Gerber Viewer

Author

Designed for the Precursor community.

Built with KiCad 8 | NextPCB Accelerator #5