FastLEd - Play animations using a MIDI keyboard

[tonio1206]

Hi everyone,

I would like to control a WS2812B LED strip using a MIDI keyboard.
The idea would be to assign animations to keys of the keyboard. I found some animations on this website:

Arduino - LEDStrip effects for NeoPixel and FastLED

I managed to play an animation when pressing a key. But I would like the animation to stop if I release the key. And to play another one if press another key.
However, I know there is an issue with interupts.

Do you think this is feasable?

I hope this is clear.

Many thanks.

[alto777]

@tonio1206

Do you think this is feasable?

Yes. It may be enough to rephrase your effects using non-blocking code. Then they run when you want, as long as you want until you decide to give no more attention to the code they use.

See if this makes sense, all I can offer just now from under the umbrella on a tiny screen:

Multiple Concurrent Effects on one LED strip

I am using an arduino uno. Is this possible? Yes. The sort of thing Paul talked about is known as a state machine and we get asked many times a day about these. So that is the sort of word you should be using to search. The principles are here:- http://www.thebox.myzen.co.uk/Tutorial/State_Machine.html Or Robin2's several things at once http://forum.arduino.cc/index.php?topic=223286.0 I have posted an example of this for WS2812 LEDs many times before, here it is again. // Multiple patt…

HTH

a7

[PieterP]

Make sure you understand this before you start:

Interrupt problems

[tonio1206]

Hi @alto777 ,
Thanks for your answer. Makes sense! But I have a qestion..
I understand what you mean by non-blocking code. But animations are usually for loops. So how can I break a loop when I release a key?

[tonio1206]

Thanks @PieterP . I will try to understand that

[alto777]

@tonio1206

But animations are usually for loops.

Mine aren't. Mine are programmed as functions that, when called, take one step of the animation, if it is time to show the next "frame" of an effect that plays out over time.

Naive code uses for loops and dealy() to do the timing. It's harder to break into that until they are finished. Looping.

If I want an animation to stop, I just don't call the function that steps it along anymore.

It seems like you might not have taken the link I posted, which is to a discussion and code examples that show this idea. The code shows how a function can be written so that calling it every 50 milliseconds (say) will let it publish a new step.

It needs embracing the concepts you will come across if you googled

arduino blink without delay

and

 arduino two things at once

and

 arduino finite state machine

There are some hacks that you could try instead, see

How to End a Loop instantly

One quick and dirty option is to write a 'myDelay()' function that checks the button while waiting for time to expire. If the button is pressed, have it return 'true'. If the time expires, have it reurn 'false'. Then, in your code, replace "delay(100);" with if (myDelay(100)) return; The 'return;' statement will exit from loop() which will then be called again and will detect that the button is pressed. bool myDelay(unsigned long delayTime) { unsigned long startTime = millis(); whi…

for example. Some are offended by such hacks - I don't argue with success and that approach def works and is easy to see why and wouldn't require a complete change in how you do this kind of thing.

Which way of doing things is still good to,learn at some point, as some,e hacks will on,y get you so far and can be kinda messy.

HTH

a7