> > Really? I'd have thought an 8x8 square with no external parts. Drive
the
> > rows with portD and read the columns with portB interrupt on change.
I'm
> > not familiar with MIDI, but certainly I'd have thought the other 17 IO
> > lines would be enough to implement it.
> >
> > As others are fond of saying "engineering is the art of compromise"
>
> For midi ouput I think I need only one data pin, maybe an extra for
> control so that's no biggy. But can I take stock 4x4 keypads and wire
> them up 8x8? Problem is, I've never actually wired up a keypad. So while
> I want it to be efficient, I'd rather use a less confusing set up then
> anything else. Pin efficiency aside, what would be the most beginner
> friendly?
>

Well, I'm only guessing about how your keypads are arranged, but the
typical matrix arrangement will have one line for each column and one line
for each row:


                             |      |      |      |
                      -------+------+------+------+
                             |      |      |      |
                             |      |      |      |
                             |      |      |      |
                      -------+------+------+------+
                             |      |      |      |
                             |      |      |      |
                             |      |      |      |
                      -------+------+------+------+
                             |      |      |      |
                             |      |      |      |
                             |      |      |      |
                      -------+------+------+------+

Generally you set this up where the rows are hooked to input pins and have
pull up resistors. Then you cycle through the columns pulling them low one
at a time and checking for lows on the row inputs. (indicating a button
pressed) (you could also hook it up the other way, with the rows as scanned
outputs and the columns as inputs, but you get the idea :-)

Seems easy enough to connect several keypads together to build a larger
matrix, yes?

As for beginner friendly, I cannot stress this enough, start small and add
to it. Start with blinking an led, then go to four leds - hey that looks
like scanning the keypad ;o) Building blocks, just add one piece at a time.

Good luck
-Denny

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