[sdiy] MIDI I/O c code..

Mikko Helin maohelin at gmail.com
Fri Mar 20 06:39:25 CET 2020


>Running status are ignored here
So you are ignoring the data bytes that belong to next note on which is
using running status, meaning the sender does not send the same status byte
again but just skips it and just sends the key and velocity bytes?


pe 20. maalisk. 2020 klo 3.29 Jean-Pierre Desrochers <jpdesroc at oricom.ca>
kirjoitti:

> > Are you handling running status and note off sent as zero velocity note
> on?
>
> Yes I handle both.
>
> Running status are ignored here,
>
> And I consider both NOTE OFF and NOTE ON with zero velocity
>
> As the end of a note.
>
>
>
>
>
> *De :* dougall [mailto:dougalli at gmail.com]
> *Envoyé :* 19 mars 2020 21:06
> *À :* eidorian at aladan.net
> *Cc :* Jean-Pierre Desrochers; Synth-diy at synth-diy.org
> *Objet :* Re: [sdiy] MIDI I/O c code..
>
>
>
> Are you handling running status and note off sent as zero velocity note on?
>
>
>
> -d
>
>
>
> On Fri, 20 Mar 2020 at 11:55, <eidorian at aladan.net> wrote:
>
> Sorry, I don't have example code for you, but here is some analysis that I
> hope might help point you in the right direction:
>
> 20MHz / 31,250Hz => ~640 instructions per MIDI data bit, or 6,400
> instructions per MIDI data byte.  That's quite a lot of instruction
> execution time between notes, so I'd be checking the
> efficiency/optimisation of the code.
>
> How long is it taking to update the analog outputs and do other
> processing?  If it's updating all 8 CVs via a "slow" protocol like I2C
> every time it loops then that might be taking a while, and maybe you need a
> different approach (i.e. only update a CV output when it changes).
>
> How have you implemented the FIFO?  Do you have locking to ensure the
> interrupt isn't writing to it while the main loop is updating it?
>
> Create a debug version that has checks on the FIFO size in the interrupt,
> and sets an LED on if it overflows, so you can confirm for certainly
> whether or not that's the problem.
>
> What I do (with 30+ years of programming experience) is pretend I'm the
> CPU, and "execute" the code in my head (or on paper if complex) in order to
> try to work out what unplanned or unexpected things might be happening to
> cause the problematic behaviour.
>
> Cheers,
> A.
>
> ---
>
>
>
>
>
> On 20-03-2020 11:14, Jean-Pierre Desrochers wrote:
>
>
>
> I’m working on a new polyphonic MIDI to CV module (8 voices).
>
> So far I did my tests with an old PIC16F887 @ 20Mhz micro I had on hand.
>
> I use a USART interrupt driven c function to ‘catch’ all the incoming MIDI
> bytes.
>
> My code is pretty fast, but still, since I only read one MIDI channel
> (1-16) at the time
> when I play very fast chords on an external keyboard
>
> all the notes are read in the incoming queue but sometimes
>
> I get stuck notes or unread ones..
>
> Same thing happens when playing MIDI files on Cakewalk SONAR
> feeding my prototype with  a MIDI cable.
> The interrupt function grabs each incoming byte and put them
>
> In a receive buffer of 32 bytes and the main () reads and treats them in a
> FIFO manner
>
> Later in the main loop.
>
>
>
> *-Would a 32Mhz micro do a difference in the USART interrupt reading speed
> ?*
>
> *-And is 32 bytes long enough for the RxBuffer to handle a 6 voices chords
> ?*
>
> *-And finaly I checked the web for a ‘decent’ C code examples*
>
> *  for MIDI reception (MIDI Tx is much easier to implement) with no
> success..*
> *  ‘Obscure’ Arduino libraries all around with no explainations of its
> inner code.*
>
>
>
> Did anybody use good C code available ?
>
> JP
>
>
>
> Synth-diy at synth-diy.org
>
>
>
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