electronicsDesigning your own RNode
Reticulum is a very cool network stack made by Mark Qvist. It can work over Ethernet and wifi, but also over LoRa with the use of RNode modems. These are readily available development boards with an ESP32 processor and a LoRa radio which, with the right firmware, make the RNode modems. But it is also possible to make your own homebrew RNode modem. The problem is that it is not well documented how to do that. This page is my attempt to alter that.
2025-03-31
The basics
A typical RNode is nothing more than an ESP32 micro controller and a
LoRa radio. It connects to a host pc running the Reticulum stack via a
USB connection. The firmware for the RNode supports various ESP32
development boards like the onces from LilyGo and Heltec. The firmware
can be installed automatically via the command rnodeconfig
and I am impressed how user friendly that implementation is.
But the supported boards all come with low power LoRa modules with an output power between 14 dBm and 22 dBm. As a ham, I want (and am allowed) to transmit with more power. Some off the shelf LoRa modules are capable of producing up to 33 dBm of power. But there are no supported development board available with these high power LoRa modules installed. So I have to design my own board and alter the RNode firmware.
The hardware
The hardware couldn’t be simpler: an ESP32 S3 connected to a LoRa transceiver via the SPI bus. Any ESP32 S3 board wil do: a development board or just the bare ESP32 S3 module. If it has I/O pins which can be used for the SPI interface, it will work.
The following LoRa modules are supported by the firmware:
- Semtech SX1262
- Semtech SX1268
- Semtech SX1276
- Semtech SX1278
- Semtech SX1280
Waveshare ESP32-S3 Pico Development Board with SX1278 and SX1268
LilyGO T7-S3 ESP32-S3 Development Board with SX1278
The firmware
Most of the work was to figure out how to alter the firmware to let
is work with my homebrew boards. It is not possible to just program the
board with rnodeconfig -autoinstall as the precompiled
firmware is not suitable for my boards. So I have to alter the source
code and compile it myself. I documented this process and published it
on my git repository: HOWTO
change firmware and compile it
On this git repository you can also find the alterred source code: https://git.meezenest.nl/marcel/RNode_Firmware_CE
Conclusion
Building a homebrew RNode modem can be done and is, in fact, fairly easy once you know how to do it. But that process wasn’t well documented. I hope that with the publication of this page, others can now build there own RNodes more easily.