This repository contains a trivial program to set the frequency based on the demo code at https://www.qrp-labs.com/synth/si5351ademo.html It has been tested on a Raspberry Pi 4, but will probably work on any Pi or similar device. Some setup is required to enable the I2C peripheral. See https://learn.adafruit.com/adafruits-raspberry-pi-lesson-4-gpio-setup/configuring-i2c The `test` program that is built will set the output frequency to 4 times the first command-line argument. The 4x multiplier is intended for driving a receiver with a quadrature clock divider, like the QRP Labs receiver: https://www.qrp-labs.com/receiver.html