Connect a 4 x 4 keyboard using only one pin.

There was an article in 'Electronic Design' May 1998 issue that connected a
4 x 4 key matrix to a single I/O pin. By using resistors between the columns
and rows and connecting them to a  cap. The cap is then discharged (by
making the I/O and output and driving it low), then change the I/O to an
input and measure the length of time it takes to charge the cap.

michael

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