[sdiy] polysix keyboard interface help

[Peter Ullrich]

Hi!

> There is no ground involved in the keyboard circuit. Those 16 lines are
> divided into 8 outputs (going into the keyboard) and 8 inputs (reading
> from the keyboard), with the key contacts indeed sitting at 61 of the 64
> matrix positions. Usually, there are diodes in series to each contact,
> in order to prevent unwanted effects if multiple keys are pressed at the
> same time (some people tend to do so when playing on a polyphonic
> keyboard... ;-)
> The microcontroller sequencially activates one of the outputs and reads
> the 8 inputs, repeating that for all 8 outputs. Using this, it can query
> any key contact.
> I have no idea how the keys are ordered within the matrix, but usually the
> keys are simply assigned from bottom to top in groups of 8 to matrix
> rows or columns.
> 
> So, it's not a matter of connecting certain lines to ground, but instead
> connecting an output to an input of the matrix, just like a keyboard
> contact does. 
> This could be done using lots of CMOS switches, but it should be
> possible to use 8 octal buffers, gated by the 8 microcontroller outputs,
> each buffer providing data for the 8 inputs. 

This is what I did for my Poly61 midi interface - I used four MT8816 matrix 
circuits and added decoupling diodes. This made a nice and quite universal midi 
interface. But quite expensive due to the big PCB and the expensive matrix 
chips.

> If the source is using a microcontroller too, it might be feasable to
> read the Polysix's 8 output lines by the interface processor, and then
> matchingly outputting 8 bits from the interface into the 8 Polysix input
> lines. I have no idea about speed requirements, but I'd guess that
> today's processors should be fast enough to satisfy that ancient Polysix
> contoller in time.

Have a look at this nice interface:
http://members.aon.at/virtual-music/zonen_e/e_products_korg.htm
It works with a PIC16F84 and works fine! (I have one of these).

Ciao
Peter

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                               Ing. Peter Ullrich   
	               Hardware & Software Developer  /  Electronic Musician
                               Private Homepage: http://www.ullrich.at.tt
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