[sdiy] MIDI Clock sync advice

[René Schmitz]

On 15.03.2024 09:29, Spiros Makris via Synth-diy wrote:
> Roman Sowa wrote:
> > And it's pretty easy to do, as MIDI clock message has no dependencies at
> > all, it can even go between bytes of single note message. Just look for
> > F8 in UART register and bam!
> >
> > I'm a bit surprised that such powerfull processors as used in arduinos
> > can't handle increased traffic, while everything needed to be done in
> > any MIDI receiver can be easily handled within one byte transmission,
> > that is 0.3ms. OTOH I don't use arduinos or libraries so what do I know.


The speed of processors roughly keeps up with programmers ability to 
waste it.


>
> While I'm a big supporter of frameworks like arduino, many libraries 
> tend to be extremely inefficient. MIDI implementations are a prime 
> example; most I've found floating around work with polling rather than 
> interrupts.


I tend to agree with respect to arduino and libraries. I've used AVR 
long before arduino even became a thing, and found it rather limiting in 
the beginning.

My gripe is that, for beginner programmer, it does not necessarily teach 
good practices, and even for a seasoned one it proliferates some bad 
habits.  (How often is everything in loop()...)

It's like giveing you a nice sugar coated piece of cake, so you might 
never be motivated to learn how to bake a better one.


Back to MIDI: generally, when using the serial interrupt you have two 
choices:

Either make the ISR short, and for example just throw the data into a 
buffer.

Or do all the processing (which could take some time) there. Risk is 
that you might block other ISRs, such as timers, which is of course bad.

In the former case you still have to poll the queue at some regular 
short interval to do the processing.

You should probably do the clock related timekeeping, processing right 
in the ISR.


So I can see how the authors of a library end up saying: I don't care. 
Let's poll the whole thing, and not bother with the interrupt.

Especially since there would otherwise be inevitable  resource clashes 
with other libraries which would drive users mad. (How servo libs grab 
the various timers for example.)

What the arduino framework would need, is a mechanism to manage call 
backs on the various interrupts.


Best,

  René



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