Fw: [sdiy] Midi Scanners

[Theo]

> D*epfer makes a key scan unit.
> But there are other options too.
> Look here for a diy example using a CV pedalboard with a midiconverter,
> actually he (ab)used a midi knob box for this.
> http://www.geopath.com/~jraden/pedals/stampPedal.html
>
> I've taken another approach using a AVR uC (90S2313)
> Its the smallest AVR with a UART (midi) has more than enough speed and is
> quite cheap.
> My pedalboard comes from a pipe organ so I didn't have much work there.
> The board has 28 keys but I do a scan for 32 keys, the remaining 8 key
> contacts are used for programming.
> So far only 4 of these are used for selecting the midi channels and the
> "split" point (two points, may overlap)
> 1) highest note of zone 1
> 2) lowest note zone 2
> 3) midi out channel for zone 1
> 4) midi out channel for zone 2
> Programming works like this, hit one of the function buttons and next a
> pedal to set the value.
> The idea is to have velo sensitive pedals, but I didn't implement this
yet.
> Midi input is also without function at this time
>
> The 20 pin AVR is hooked up like this.
> Five Pins PB0 to PB4 address 32 x 2 opto interrupters
> PB5, 6, 7 are only used to (re)program the device
> Midi I/O is on pins PD0 and PD1
> Pins PD2, 3, 4 are free for future use ;)
> And PD5, PD6 read back the key position
>
> The program is rather simple;
> Have a endless loop do a counter on PB0..4,
> read back the key positions and compare to a array with key positions in
the
> ram.
> If the position changed, write to a buffer and start a interrupt process
to
> sent the midi message.
> If a function button is pressed, jump to the appropriate sub routine.
> The rest is a matter of "mooi zitten, dom kijken en lang volhouden"
>
> To get the velocity to work you need a bit more complicated program using
a
> timer for the keyscan.
>
> I used opto interrupters, but this calls for some care in power management
> (multiplexing 64 leds) and construction (light proof).
> Next time I would probably use reed contacts.
>
> Cheers,
> Theo
>
>
>
>
>
> From: Christopher Hopkins <synthdiy at operamail.com>
>
> > Hi Everyone,
> >
> > I'm interested in building a very simple midi pedal (ala Moog Taurus) to
> > control my Juno-106 when I'm playing the guitar.  I've seen a few
designs
> on
> > the net but they all used the Midi Scanner by Maplin, which is no longer
> > available.
> >
> > Does anybody have a schematic for the Maplin Midi Scanner or another
> > implementation?
> >
> > Many Thanks
> >
> > Chris Hopkins
> >
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