[sdiy] How to add MIDI IN to an old Casiotone 101

[Steve Ridley]

It's worth noting that in many early Casiotones, the matrix scanning included the keys, the instrument's switches and sometimes some "hidden" features.

So, if you just add a standard 8x8 (or 8x7?) matrix scanning Midi upgrade kit, some notes off either end of they keyboard may do unexpected stuff like introducing vibrato or sustain. Certain key combinations may even allow patch changes. Hidden features may include different mod depths or rates.

Before you start upgrading your Casiotone, you could spend some time prodding about carefully with with a diode, finding what all the matrix switch positions do. Robin Whittle published some related information here:

http://www.firstpr.com.au/rwi/casio/

If you can customise your midi mod, you could add mod, sustain, maybe patch change etc.


Steve




> I have this old board, it's provides quite basic digital sounds from an NEC D990G chip. As far as I can tell, this chip also performs the matrix scanning of the keybed.
>
> So if one were to add MIDI to it, this is how I envisage it:
>
> 1. MIDI note-on message received 
> 2. Microcontroller interprets note and uses a look-up table to tell it which position of the matrix this note fits.
> 3. Microcontroller waits until the switch for the notes row goes high
> 4. Microcontroller sends the correct pin high for that note.
> 5. Pin stays high until note-off is received.
>
> So the micro would have to sync (or at least follow) the onboard chips scanning and just output the 5v for that note at the correct time.
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