Check out Multirotor Guide It gives you the most straightforward and informative explanation about Smart Audio.

What you will learn in the guide: 

  • What is Smart Audio?
  • How to Connect VTX to FC with Smart Audio
  • Set Up Smart Audio in Betaflight
  • CLI Commands
  • Betaflight OSD
  • VTX Control via LUA Script

(Below is the screenshot of the guide )