[sdiy] MIDI Router

[Matthew Smith]

Quoth Scott Nordlund at 2009-04-11 10:41...
> It would be a lot easier to just use switches.  
>I don't know how often you'd really need to go
>messing around with it, but for my purposes at
>least it would be more or less "set and forget".
>You'd need a microcontroller if you wanted to
>merge/filter/etc. (in which case you'd do the
>routing in software rather than using the
>multiplexers) or to store settings, but for
>simple routing I don't know how much useful
>functionality it would really add.

Have to agree to disagree on that ;-)

The whole reason for having this device is to be able to change routings
frequently - especially the MIDI outs of modules going to the computer
for backups.  I can send patch changes quickly and easily from my K5000
workstation.

As regards microcontrollers, I come from a very much digital background
and, for me, they are often the simplest and economic solution for a
whole host of applications.  Also a big fan of distributed computing -
inclined to use several slow/cheap devices rather than one big, fast,
expensive one.  I2C, SPI can make life easy. (That will require more
complex programming and also be a pig to solder!)

I looked at using a microcontroller for routing when I first considered
this but then realised that I would need something very fast to do so,
if I were to scan 8 (or more) inputs running at MIDI Baud rate, then
reproduce the incoming state on the outputs.  Note that this isn't just
an 8 into 1, it could be up to 16 into 16 which would require a heck of
a sampling rate which would entail the use of devices that I'm not
familiar with programming and have not-so-friendly SMD packages to solder.

Using multiplexers means that I can use a pair of slow, $3, uCs and 8 x
$0.25 mux devices to do the job.  (Using the extra uC(s) because it's
easier (for me) and cheaper than buying latches and decoders.)

You mention mergers - yes, I'm thinking of making provision for adding a
couple of them.  If I present the thing as a 12x12, I have a) room for
expansion and b) 4 inputs and 4 outputs that may be used internally for
merges, arpeggiators and anything else that I might decide to throw in.

Cheers

M

-- 
Matthew Smith
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