[sdiy] MIDI Router

[Matthew Smith]

Hi Folks

Just looking for some feedback on something I am planning to build.

My current set-up consists of a Kawai K5000W workstation (additive
synthesis,) Korg MS200R and Roland MKS70 modules plus a pair of vintage
Akai samplers.  I have plans (but very vague ones) for a home-brew
hybrid synth and (less vague plans) for MIDI control surfaces for the
Kawai and the Roland.  Oh, and an Alesis SR16 drum machine.

After working out that I would need more MIDI interfaces than I have USB
ports on my [Linux] laptop (will be running the Qtractor DAW,) I had
another look at my gear to see what I really needed.  The issues that I
feel need addressing are:

* Backing up modules using MIDI SysEx - need as many MIDI ins to laptop
as there are modules doing this.
* Recording patterns from the Alesis to either the laptop or the
workstation (in real time.)
* Latency from using MIDI through.
* MIDI routings getting to damn complex. Example: why am I not getting
MIDI data on unit x?  Because it's at the end of the MIDI through chain
and one of the units in the middle is switched off.

The logical solution would appear to be to have the MIDI ins and outs of
every unit connected to a single patch/hub/router or whatever you want
to call it.  Every in can be routed to every out.

An simple 8 in x 8 out unit could be built simply by using a 74HC151 mux
for every output and a microcontroller (or possibly 2 microcontrollers -
cheaper than using latches!) to control them.  By multiplexing the
multiplexers (say with 74HC157s) we could easily go to a 16x8 or, by
duplicating the 74HC151s as well, having a full 16x16 unit.

The uCs could be controlled from some sort of front-panel control and/or
MIDI.  (Add another 74HC151 and we could select not just the MIDI
channel used to control the device, but the port as well.)

My main question is which MIDI controller would I use for selecting
patches? (Note that an 8x8 or a 16x8 unit would work fine here but a
16x16 could complicate the MIDI implementation if we only have 7 bits
from which to select.)

Any other comments/thoughts on this concept?

Cheers

M

-- 
Matthew Smith
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