system.highlight with color LED deck

[ntamas]

It seems like only the LED ring deck responds to setting the system.highlight parameter to 1 by flashing the LEDs briefly. We use this parameter in Skybrush to allow the GCS operator to highlight a drone during preparations so it would be nice if this parameter also worked with the color LED deck. Would you be open to accepting a PR that implements this?

My plan would be probably to extend ledDeckHandlerDef_t in led_deck_controller.h with a highlight() callback that LED decks can fill in (or leave unimplemented). Setting system.highlight to 1 would then call a callback (using PARAM_ADD_WITH_CALLBACK), which in turn calls the callbacks for all registered LED deck controllers.

(Note: I will probably do this anyway for our Skybrush fork of the Crazyflie firmware as it is the easiest way to allow Skybrush to work with the LED rings as well as the color LED deck, I'm mainly interested in whether this would be good enough for inclusion in the next version of the firmware officially).

[gemenerik]

Yes, we'd be happy to take a PR for this. Thanks!

led_deck_controller.h is the right place for it.

One thing to watch in the implementation: parameter callbacks are invoked synchronously from the param write path, not from the deck's own task. So the per-deck highlight() should only latch state.

[ntamas]

In the meantime, I was thinking about alternatives because the "highlight" operation could in theory be handled by other decks (e.g., the buzzer deck could emit a sound). So we actually have two options: one that I described above, and one where we define a highlight module (similarly to the led_deck_controller module) where decks can register callbacks that get invoked whenever the user submits a highlight request. Feels a bit overengineered for me but I don't know which direction you guys would prefer so I'm happy to implement either, just let me know.

[gemenerik]

We like the idea. Also because it wouldn't have to stop at decks. The Crazyflie itself could answer a highlight later with onboard LEDs or even by beeping the motors.

But it's not required here. Your branch already shows: system.highlight keeps the same name, type and semantics wherever the dispatch lives, so moving it later is an internal change no client would notice. But if you are up for it, we would very much welcome it.

[ntamas]

Work started here: https://github.com/skybrush-io/crazyflie-firmware/tree/feat/system-highlight-color-led-deck

Not fully fleshed out yet, just curious if I am on the right track with the implementation.

[gemenerik]

Right track!