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MBFM and MBSEQ V4 coupling problem [solved]


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I can't exactly figure out where to post this, so let it be here.

I have a very strange bug:

When i connect my LPC17 MBSEQ to MBFM it seemed like there's no midi data received by MBFM.

BUT! When i connect it via midi thru enabled device (like Midipal or Shruthi) - all ok. When i connect midi keyboard directly to MBFM - all fine. And connection to midi port of PC also gives me good result.

The MBSEQ works fine, being directly connected with Shruti, Midipal and PC.

When i connect midi cable (with other end in the air) to MIDI OUT of MBFM - some midi data appears, but with a lot of dropped out notes.

Non working config:


Working config:






Half working config:


Scratching my head.... :unsure:

Edited by Schrabikus
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Hehe, sometimes problems have to be formulated in writing. Yes, it's low voltage related. I've look to schematics of Midipal (3.3 v midiout too) and removed/replaced 220 ohm resistors at all outs like schematic.


Now all works fine, but with a little bug (or feature?) - opened and closed HH can't play simultaneously. Is it OPL3 restrictions or smth wrong with my MBFM?

for example in this case OH somtimes triggered, sometimes not. It's random alike thing.

OH ....*.......*...

CH *...*...*...*...

But when there's no overlapping between them - they played correctly.

OH ....*.......*...

CH *.......*.......

Edited by Schrabikus
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Open and Closed HH can't be played at the same time, because they share the same voice.

Btw.: similar to a TR808, "good" sample based drum samplers which allow to group samples, and a real HiHat! ;-)

Best Regards, Thorsten.

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Every drum machine I've used has imposed the open/close hihat restriction. I would imagine most units do this in software, the RY30 I used allowed you to configure the grouping.

As the OPL chip was designed for soundcards I can only assume they didn't trust the people writing the drivers to implement this feature and so they did it a chip level.

As for why it randomly works and doesn't work sometimes, MIDI can't guarantee that events are delivered on time, it's a serial protocol at a low data rate. The more busy the bus the more jitter you can encounter.

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