On Tue, 03 Sep 2019 13:06:58 -0400, Dennis Lee Bieber wrote:

> On Tue, 3 Sep 2019 07:39:14 -0400, "J.B. Wood" 
> declaimed the following:
>
>>Hello, all.  Just thought I'd revisit this topic since it's been a
>>while.  Has anyone ever constructed a Pi-based standalone 1-2 channel
>>MIDI sequencer?  By standalone I mean it has an integral display and
>>required pushbuttons/rotary knob for device control.
>>
>  What do you intend to show on the display?
>
>  What type of control do you envision? (If you visualize a one/two
> octave keyboard, you then have to specify how many notes in parallel --
> one note at a time can use a simple row/column keyboard scan -- but when
> you go beyond two notes such a matrix can generate ghost key presses;
> avoiding ghosts requires a linear matrix, which means LOTS of GPIOs -- a
> 1x24 would need 24 GPIOs to detect key presses, while a 4x4 is only
> using 8 GPIOs for 16 keys)

Not Necessarily so. To eliminate ghosting you simply need a diode on each
switch (how do you think a quality computer keyboard manages N Key
rollover?).
16 io pins gets you 8*8 = 64 keys so a full piano (81 keys if i remember
correctly) still only requires 9 by 9.


--
God must have loved calories, she made so many of them.

--- SoupGate-Win32 v1.05