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Matrix midi wiring

Building organ consoles for use with Hauptwerk, adding MIDI to existing consoles, obtaining parts, ...
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OPUS1883

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Matrix midi wiring

PostWed May 18, 2016 2:06 pm

Hi, can someone explain to me how the matrix midi wiring system works... i still cant figure out how if more than one note is fed into a midi port, how the input knows which octave to sound out...

Chris
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engrssc

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Re: Matrix midi wiring

PostWed May 18, 2016 2:48 pm

Pure magic is how it works. 8)

I do hove a good explanation somewhere in a file that I can post when I get back home. It's really quite simple. No doubt others can explain it as well.

Rgds,
Ed
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jkinkennon

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Re: Matrix midi wiring

PostWed May 18, 2016 4:32 pm

One column of the matrix is activated at a time, typically by setting that line to ground potential while the other columns remain at a positive voltage, let's say +5v. All the rows are pulled high through resistors. Anywhere a key contact (at a column/row crosspoint) is closed the corresponding row gets pulled low. The CPU reads the row voltages for the activated column and then the next column is activated.

There are diodes in series with each crosspoint key contact which keep 'ghost' keys from sounding. That's a bit more complicated.
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mdyde

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Re: Matrix midi wiring

PostThu May 19, 2016 3:55 am

[Topic moved here.]
Best regards, Martin.
Hauptwerk software designer/developer, Milan Digital Audio.
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NickNelson

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Re: Matrix midi wiring

PostThu May 19, 2016 4:40 am

Hi Chris,

jkinkennon's description of how the matrix works is clear enough, but I think that the point you are missing is that MIDI isn't involved at all in this part of the circuit.

All the matrix wiring (and the switch contacts connected to it) does is to allow a further block of circuitry (the 'encoder') to determine which switches are open or closed at any particular time. The advantage of the matrix wiring arrangement is the simplification of only needing 16 wires connected to the encoder rather than the 62 wires which would be needed if each switch was connected to the encoder individually.

It is the encoder (rather than the matrix) which transforms the information from the switches into MIDI messages and sends these messages on to the MIDI port on the computer.

If you want to know how the MIDI encoder does this, and what the messages look like, just ask again.

Nick
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elia

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Re: Matrix midi wiring

PostFri May 20, 2016 11:13 am

Well said Nick,
also for a double matrix (velocity enabled) you have to know the min...max switch time (about 1...x ms) and the digital MIDI resolution that you want (from 1 to 14 bit CC#88 http://dev.midi.org/techspecs/ca31.pdf ). The diode responds after 1us and this fact is a limit to the resolution (up to about 12 bit).

There are also optical and magnetic solutions that meet exaggerated requirements:

14bit magnetic
http://www.infiniteresponse.com/

12bit optical
http://www.flkeys.at/home.html
Elia

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