Generic Calculator Shield for Arduino Photo-journal

[Marcus von Cube]

(03-23-2015 05:29 PM)matthiaspaul Wrote:  While a typical keyboard matrix reduces the number of necessary I/Os for (N/2)^2 keys to N already, using some diode tricks you can increase the number of necessary keys to N^2-N. That is, with four I/Os and four diodes you can already decode twelve keys (instead of four), with six I/Os and diodes thirty keys (instead of nine), and with eight I/Os and diodes 56 keys (instead of sixteen).

This sounds interesting. Can you explain the trick in some more detail? Will it allow the detection of keys being pressed simultaneously (n-key roll over)?