RNode Linux

RNode Linux is a userspace Linux implementation of an RNode-compatible transport for SPI-connected SX126x LoRa radios. It reads board-specific GPIO and SPI settings from a YAML file, initializes the radio, and exposes a TCP socket that carries RNode/KISS traffic for a host application such as Reticulum.

The current implementation is intended for Linux systems that provide:

• An SX126x radio connected over spidev
• GPIO access through libgpiod
• A YAML configuration file describing the SPI device, control pins, and TCP port

What the daemon does

At startup the daemon:

1. Loads a YAML configuration file
2. Opens the configured SPI device
3. Requests the configured GPIO lines for chip select, reset, busy, DIO1, RX enable, and TX enable
4. Starts a TCP listener on the configured port
5. Translates traffic between the TCP connection and the SX126x radio using the RNode/KISS protocol

Only one TCP client is accepted at a time.

Prerequisites

You need a Linux system with the following available:

• A C compiler toolchain such as gcc
• cmake 3.16 or newer
• Development headers for libgpiod
• Development headers for libcyaml
• Linux SPI support with an exposed device such as /dev/spidev0.0
• Access to the relevant GPIO chips and SPI device at runtime

Typical Debian or Ubuntu package names:

sudo apt install build-essential cmake libgpiod-dev libcyaml-dev

Before running the daemon, make sure SPI is enabled on the target system and that the process has permission to access both the spidev device and the GPIO controller.

Build

Configure and build with CMake:

cmake -S . -B build -DCMAKE_BUILD_TYPE=Release
cmake --build build

The resulting executable is:

build/rnode

Install

The project defines the following install targets:

• The rnode binary to PREFIX/sbin
• The example configuration file to PREFIX/mnt/rns/rnode.yaml

Install with the default CMake prefix:

sudo cmake --install build

If you specifically want the files installed as /sbin/rnode and /mnt/rns/rnode.yaml, install with --prefix /:

sudo cmake --install build --prefix /

Run

Run the daemon by passing the path to a YAML configuration file:

./build/rnode ./rnode.yaml

Usage from the program itself:

rnode <config_file.yaml>

The daemon logs to syslog using the rnode ident.

Configuration

The configuration file is YAML and must contain these keys:

spi: /dev/spidev0.0
cs: { port: 0, pin: 21 }
rst: { port: 0, pin: 18 }
busy: { port: 0, pin: 20 }
dio1: { port: 0, pin: 16 }
rx_en: { port: 0, pin: 12 }
tx_en: { port: 0, pin: 13 }
tcp_port: 7633

Field meanings:

• spi: path to the Linux SPI device used for the SX126x radio
• cs: GPIO chip index and line offset used as chip select
• rst: SX126x reset line
• busy: SX126x busy line
• dio1: SX126x DIO1 interrupt/status line
• rx_en: external RF switch RX enable line, if present on the board design
• tx_en: external RF switch TX enable line, if present on the board design
• tcp_port: TCP port used for the single client RNode/KISS connection

The repository includes an example configuration in rnode.yaml.

Notes

• This project is currently tailored to SX126x-based SPI modules.
• The daemon binds to 0.0.0.0 on the configured TCP port.
• The code links against libm, libgpiod, and libcyaml.