Key-reading circuit saves I/O pins


Posted on Jul 7, 2012

Some microcontroller applications usually use too many I/O pins to read keys or onboard switches; in many cases, few pins remain available for other uses. Some alternative ways to read keys yield more free pins. First, consider some ways to effect key reading. Table 1 presents a comparison of four methods with references to circuit configurations (Figure 1, Figure 2, Figure 3 and Figure 4).






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