This Arduino software supersedes the Arduino firmware G8JCFSDR Build 280 to control the Elektor SDR Shield 2.0 (1).
You can compile it for every kind of Arduino, even an ESP32.
It uses the standard library Si5351 Library for Arduino by Etherkit which can be installed within the Arduino library manager.
This firmware is only compatible with the build 280 of G8JCFSDR.
Links: