[sdiy] MIDI velocity

rsdio at audiobanshee.com rsdio at audiobanshee.com
Thu Apr 7 00:30:57 CEST 2016


On Apr 6, 2016, at 3:21 PM, "Richie Burnett" <rburnett at richieburnett.co.uk> wrote:
>> I would recommend using a matrix where the two switches for any given key are on the same column.
> Unfortunately, that's not how the matrix is wired up on the keybed.  The "rows" and "columns" of the matrix are wired up differently.

Differently?

How are the keys grouped? Usually, a given octave is on the same column, such that scanning through successive columns ends up moving across the keyboard from left to right. Usually, a column only has eight rows, so that's less than a full octave per column, but approximately equivalent.

I'm assuming that a velocity keyboard would have approximately the same wiring, except that it would take three columns or more per octave. Again, if there are eight rows per column, that's enough for four keys if the two switches per key share the same column.

The worst way I could imagine would be for one set of columns to contain the first switch, and then an entirely separate set of columns would contain the second switch. Then, the firmware would have to scan all the first switches in one pass, then the second switches on a second pass. Of course, even that wiring couldn't prevent the firmware from scanning the columns in a different order to keep the reads localized to one part of the overall key bed at a time.

I suppose I could just look for schematics of any velocity keyboard, and it would show a typical wiring...

Brian




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