[sdiy] MIDI velocity

P Maddox yo at vacoloco.net
Sun Apr 24 23:04:37 CEST 2016


Yup, same here...

black keys seem 'quicker' than the white keys

On 24 April 2016 at 18:04, Amos <controlvoltage at gmail.com> wrote:

> I'm curious to hear if others have noted significantly different switch
> timing (relative to actual played velocity) for black keys versus white
> keys, on those Fatar keybeds.
>
> My experience is that the black keys seem "hotter" than the white keys,
> enough that I have to use separate curves for black versus white to get
> consistent-feeling MIDI velocity output.  I chalked it up to geometry and
> physics and went about my way, but I didn't notice any similar comments so
> far in this thread so I thought I'd ask if it was just me experiencing
> this...
>
> -Amos
>
> On Wed, Apr 13, 2016 at 9:24 PM, <rsdio at audiobanshee.com> wrote:
>
>>
>> On Apr 13, 2016, at 12:20 PM, Neil Johnson <neil.johnson71 at gmail.com>
>> wrote:
>> > I wrote:
>> >
>> >> About 7 years ago when I was writing the keyboard scanning code for a
>> >> Siel Opera 6 I had a simple scheme for scanning and measuring play and
>> >> release velocity (not many folks seem to know about release velocity
>> >> although some synthesizers do recognise it).
>> >>
>> >> Using an Atmel ATMega8 scanning the entire keyboard every 1ms I run
>> >> 4-state state machine for each key, where the states are UP,
>> >> GOINGDOWN, DOWN, GOINGUP, and an 8-bit counter for each key.
>> >> Debouncing is handled by the algorithm rather than a separate
>> >> debouncing step.  With the right encoding of the states you can do
>> >> most of the testing and state transitions using btiwise operations, 8
>> >> keys at a time (on a 32-bit processor you could do 32 keys at a time).
>> >>
>> >> I'll try and dig out the code and sling it up on github sometime.
>> >> It's all in C, no assembler required.
>> >
>> > Found it, and hosted up on github:
>> >
>> > https://github.com/nejohnson/kbdscan
>> >
>> > The keyboard scanner talks to a 74LS154 on the keyboard assembly, and
>> > generates key on and off events with associated velocities.  There's
>> > also code for reading some analogue inputs and a footswitch, but
>> > that's not important right now.
>>
>> Thanks for sharing this!
>>
>> I was going to suggest that having the 'LS154 on the keyboard assembly is
>> a great design choice, because that allows a simple, 14-pin connector, but
>> then I realized you probably were stuck with that choice because of how the
>> Siel Opera 6 was designed. Sure enough, looking at the schematic I see 8
>> row bits, 4 column address bits, power and ground. (feel free to swap the
>> row and column nomenclature as you prefer - Roland seems to use the
>> opposite terms)
>>
>> Brian
>>
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