SAMD21E RFM69 radio transceiver

This project is a transceiver that an be used as an open-hardware equivalent of the rflink project. Thanks to its RFM69 chip, it supports more than simple OOK, notably an encrypted FSK protocol with checksums.



The schematic is what you expect:

  • A 1A 3.3V regulator.
  • SPI between the SAMD21 and RFM69.
  • Pins D0 and D2 from the RFM69 go to interrupt-enabled pins on the SAMD21.

There are several capacitors to decouple the load from the RFM69 and SAMD21, it might not be necessary.


All components are SMD, except for:

  • 2mm pitch headers for the RFM69.
  • 2.54mm 4x1 header for debugging.
  • SMA connector for the antenna.

It can all be milled on a single-sided copper plate. If you send the files to a manufacturer, you can have sturdier vias and cool text on the other side:


I milled mine on an FR4 board with a 1/64” (0.4 mm) flat end mill. Pro-tip: you can use nail polish to prevent the copper from rusting, just avoid connectors like the SWD and USB.

On the other side, you can mount the RFM69 and connect the antenna.

A 3D printed box protects all components and exposes the USB, coax and debugging pins.

The enclosure is closed with M3 bolts, and the nuts are hidden in little pads.

The antenna is fitted last. I picked the correct length for broadcasting 433 MHz, if you use the 868MHz variant you probably need a different length.

Here’s a size comparison with an Arduino Mega with rflink, showing the benefit of a custom board.


Coming soon!


This project is provided under the MIT License.