Ravindra Divekar wrote:
>
> somebody please tell me whether a
> X-Y key matrix is efficient, if i
> am checking for key combinations
> rather than single-key presses.
> i ask because the 16c84 has only 1k
> of code space, and key matrix
> scanning consumes a lot of space.
>
> --Ravindra

Instead of using diodes try to use transistors.

                       *---------------*
                       I               I
                   /-------\           I
                   I       I           I
                   I u-Amp I           I
                   I       I           I
                   \-------/           I
                       I -             I
                       I   BC547       I
            plate   /--I--\        /-------\
          I I       I  I  I        I       I
       *--I I----*--I--I--I        I  Vdd  I
       I  I I    I  I \I/ I        I       I
       I         I  \--I--/        \-------/
       I        III    I               I -
       I      1kI I    I               I
       I        III    I               I
       I         I     I               I
       I         *-----*               I
       I               I  pulses       I
       I           /-------\           I
       I           I  ---  I           I
       I           I  I I  I           I
       I           I -- -- I           I
       I           \-------/           I
       I               I               I
       *---------------*---------------*

Try to messure the distance between the plates with varios
frequences and Amp's.

Rgds,