This idea builds on a previous IFD, "Connect Any Keypad With Any Microcontroller Using Only One Pin" (electronic design, May 1, 1998, p. 126), where a 555 timer connects a keypad switch matrix to a ...
A previous Design Idea described a single-wire-plus-ground-return, keypad-to-microcontroller interface in which a single pulse represents each keystroke (Reference 1). The pulse's width is ...
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