[sdiy] MIDI & DIN Sync in the same connector?

Magnus Danielson magnus at rubidium.dyndns.org
Tue May 22 23:17:55 CEST 2012


Hej Mattias!

On 05/22/2012 09:41 PM, Mattias Rickardsson wrote:
> MIDI and DIN sync (in its simplest form, with just clock and
> start/stop signal) use different pins in the same connector.

Interesting thought.

> The possibility of supporting both MIDI and DIN sync in the same
> connectors have crossed my mind often during the years, but I can't
> remember seeing any products using it - apart from Dutch
> Engineers at work, who seem to have combined MIDI and DIN sync connectors
> on a couple of their products:
>
> Their 1-to-4 "Midi Thru Box" can also be used as a DIN sync thru box
> (presumably just passively connected),
>    http://www.engineersatwork.nl/dtronics/pages/midi_sync_thru_box.html
> and their "Midi to Sync converter" seems to send DIN sync signals and
> MIDI timing signals simultaneously on the same connector (presumably
> driven by the same clock pulses, since MIDI timing messages are just
> positive pulses with the same frequency as DIN sync, IIRC).
>    http://www.engineersatwork.nl/dtronics/pages/midi_sync_converter_ms06.html
>
> Are any other products using combined connectors in similar ways?

I saw a prototype of a new product which had both DIN and MIDI, but on 
separate connectors. To some degree, yes... you can do it, but it is 
just one additional connector, so it doesn't really add that much cost, 
and you don't need to figure these things out. Also, what if you want 
DIN sync and MIDI at the same time to different gear?

> I don't see any electrical reason why DIN sync OUT wouldn't be
> suitable to incorporate in every MIDI OUT and MIDI THRU connector
> (provided that the correct DIN sync signals are generated internally
> of course). Are there any reasons not to do it?

Well, if you have a full DIN cable hooking up to a box using the other 
DIN pins (those boxes does exists), are you sure that the current 
limiting resistors is there so it won't cook the diodes in your MIDI 
receiver?

> Combining MIDI IN and DIN sync IN is a bit trickier, especially since
> MIDI needs to be galvanically disconnected and since there might be
> exotic "tap", "fill in" or "reset and start" DIN sync data on the
> incoming MIDI pins, but it should be quite possible as well. :-)

Hehe, I discussed the isolation of MIDI yesterday actually...

The MIDI-standard tries to avoid grounding loops by attempting to do 
isolational bonding network (IBN) strategy, just as Ethernet tries to do 
it. If you believe it makes you happy, the MIDI standard does the right 
thing.

DIN-sync will however take the other approach (most possibly out of KISS 
and economy), it follows the mesh bonding network strategy... in which 
you just hook grounds together and if you add another link it doesn't 
really hurts because it just ties things a little tighter together.

If you hook things up with full ground, you don't really have to bother 
with the opto-isolator, but if you hook up a normal MIDI source you 
would still appreciate it.

The trouble with the IBN strategy is that you very easily break the 
rules and get a loop, so it has become depreciated. Also, it is harder 
to achieve good EMC performance in IBN. Do get ITU-T K.27 
recommendation, it's available for free download.

Anyway, in the end I lean towards saying that sure, you could try it, 
but the gain is too little most of the time, so why bother. We have 
bigger game to kill.

PS. Check your Google window now on the 23rd of May. google.ru works 
right now for instance.

Cheers,
Magnus



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