22Embedded Modules
© Tibbo Technology Inc.
Scan lines can optionally perform the second function of driving LEDs. One such LED
can be connected to each scan line, preferably through a buffer, as shown on the
diagram below. These LEDs can be used for any purpose you desire — and this
purpose can be completely unrelated to the keypad itself.
If the LEDs are connected as shown on the diagram, you will turn them ON by
settings their corresponding control lines LOW.
Binary keypads (i.e. "keypads that output binary key codes") do not require
scanning — they contain a (typically microcontroller-based) circuit that performs
the scanning and outputs encoded binary codes of pressed keys. Such keypads are
sometimes called "encoded keypads":
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