add note about compatibility

README.md

@@ -1,3 +1,11 @@
+## Important Note
+
+The firmware in this repository is compatible with the ODrive v3.x (NRND) and is no longer under active development.
+
+Firmware for the new generation of ODrives ([ODrive Pro](https://odriverobotics.com/shop/odrive-pro), [S1](https://odriverobotics.com/shop/odrive-s1), [Micro](https://odriverobotics.com/shop/odrive-micro), etc.) is currently being actively maintained and developed, however its source code is currently not publicly available. Access may be available under NDA, please [reach out to us](mailto:[email protected]) for inquiries.
+
+## Overview
+
 ![ODrive Logo](https://static1.squarespace.com/static/58aff26de4fcb53b5efd2f02/t/59bf2a7959cc6872bd68be7e/1505700483663/Odrive+logo+plus+text+black.png?format=1000w)
 
 This project is all about accurately driving brushless motors, for cheap. The aim is to make it possible to use inexpensive brushless motors in high performance robotics projects, like [this](https://www.youtube.com/watch?v=WT4E5nb3KtY).