[sdiy] MIDI Router

[Matthew Smith]

Quoth Dave Kendall at 2009-04-11 19:08...
> Have you considered crosspoint matrix ICs? .... It might make life 
> easier....
> 
> The Analog devices AD75019 is a 16 x 16,
> the Zarlink MT8816 is a 8 x 16.
> 
> I think Analogue solutions once made an audio router based around the 
> AD chip. I once looked into this *very* briefly, while dreaming of a 
> total recall system for a hardware synth. (It never happened. Well, 
> yet, anyway...... )

Thank you for that - exactly the "out of the square" thinking that I
needed ;-)

My original approach was to do it with just a microcontroller, but that
was defeated by the sampling rates that would be required to do the job.
 (Based on an 8-bit uC at up to about 20MHz.)

Second approach was to use discrete logic - took me a while to
rationalise something using about 20 low-numbered 74xxx gates to get to
the mux stage.  (I was trying to build muxes with discrete gates.  Really.)

Now I have the suggestion of the x-point analogue switch of which I was
aware but never considered for a digital application! (Doh!)

The real beauty of this approach (looking at the AD75019) is that a)
they can be cascaded and b) use what looks like a standard serial
protocol although I can't figure if it's I2C or SPI at this time of
night as they don't give it a "standard" name.  (I was informed by
someone at TI that this sort of thing is a trademark thing; I asked if
the interface on a certain TI device was anything like SPI [it sure
looked like it] and was told that it was, but the datasheet couldn't say
the name as it belonged to Freescale.)

Anyhow, this looks like an improvement of BOM cost for a 16x16, easier
programming and a nice, easy PLC44 package which is really no problem at
all to solder.  I shall sleep easy tonight!

Cheers

M

-- 
Matthew Smith
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