Ernieift has been hard at work over the last year at some really neat features to use a language called picoC in order to allow running small pieces of custom code on the flight controller. This means people can easily share code to add custom features to their flight controller that would not otherwise be easy to have in the core code. This feature is now very nicely developed, with a UI for uploading and downloading code, saving and loading to the flash chip, testing it, getting output on the console, running independently on startup, and more.
This code can access internal variables (for example the current attitude), the inputs, and also drive unused PWM outputs. Here i demonstrate using this to write a small program that drives the external LEDs on Sparky2 to make the LEDs indicate north.