@MickPF This depends on how you are doing your development. New players often start off doing some development on their Omega2x device, eventually, you realise this a short term solution since IoT devices are by design resource poor. The best way to do Omega2x development is to install the build system https://github.com/OnionIoT/source then you will have access to everything you need as well as the cross compiler, so you can use your more powerful desktop/notebook device for your development and then move the completed work to your Omega via scp/ftp. The headers and libraries you are looking for are on the Onion Github, https://github.com/OnionIoT Also refer to the docs on how to compile on the Omega: https://docs.onion.io/omega2-docs/i2c-c-library.html