[filters] delayed first order filter int

[bartslinger]

This is a integer implementation of a first-order filter, with some extra's:

• saturation on increment rate
• delay using a buffer

I use this for an INDI implementation for a helicopter, which will follow later in a pull-request.

[flixr]

Since this seems to be useful for other things as well, it would make sense to choose a more generic name than "heli_rate_filter"...
And maybe make the frequency a parameter instead of using the fixed PERIODIC_FREQUENCY

Out of curiosity: why do you want the delay?

[bartslinger]

Do you have a suggestion for the name? I can change the frequency to parameter if you like. I need delay because I use this filter also to make a model of the actuator, which responds +- 18ms after a command is applied. This gives me the estimated position of the actuator.

[flixr]

Puh... maybe something like delayed_low_pass or so??

[bartslinger]

What do you think of fancy_first_order_lowpass?

[flixr]

lol, then probably rather delayed_first_order_lowpass or something else that describes the functionality...

[bartslinger]

Ok I'll go for that

[bartslinger]

Done. Oh wait the heli rate filter thing is still there.

[bartslinger]

Done? :-p

[gautierhattenberger]

looks good to me

[flixr]

@bartslinger We could still give the struct and functions shorter (e.g. abbreviated) names if you want...
But if you are also happy with the long names we can merge it as it is now.

[bartslinger]

I'll leave it like this for now. Then I continue with my next PR ;-)