[sdiy] MIDI Sys Ex packet length

Roman Sowa modular at go2.pl
Mon May 25 08:57:29 CEST 2015


All has been said already, so just my 0.03PLN on this

I've experienced problems with packets even smaller. 128B was more or 
less the boundary of doability. Never tried cheap chinese USB/MIDI but 
those from reputable companies were also hungry byte eating. However 
this is no issue at all if you use USB/MIDI with large internal buffer 
and proprietary drivers. You all know the brand name so I'll not name it 
here.

My SysEx online generator inserts delay every each sysex package and the 
output is Standard MIDI file. Works with no problems if the user is able 
to play it anyway. Not every sequencer sends out SysEx, and even if it 
does, this option may be not active by default.

MIDI-OX puts user defined delay between sysex packets.

Roman

W dniu 2015-05-24 o 20:21, Richie Burnett pisze:
> If doing a flash update of firmware over conventional MIDI via System
> Exclusive is it wise to break the download into many smaller packets of
> say 128 or 256 bytes in length?
>
> I was planning on using MIDI-Ox for Sys Ex flash updates, but I guess I
> could also incorporate the Sys Ex packets into a standard MIDI file that
> could be played back on any capable hardware?
>
> Does anyone know if MIDI-Ox has any provision for resending packets if
> something like a CRC fails, or would I have to write my own program at
> the PC/Mac end to check for ack/nack and resend the necessary corrupted
> packets?
>
> I've already discovered that certain cheap Chinese USB to MIDI
> interfaces don't correctly handle MIDI messages containing more than 3
> bytes!!! So they're a non-starter from the outset.
>
> -Richie,
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