There are basically two methods commonly known for keypad interfacing in one
5 volts is supplied and the row and columns of the pressed key are made 0 in this way key is scanned.
But the method we used is that we made the all rows 1 (means supplied 5 (Volts) and then pressed the key and the pressed row and columns are scanned simultaneously but indirectly.
We used 4 * 3 keypad as 4 * 4 was not available in market. so we have 4 rows and 3 columns in our keypad which is actually a digital phone keypad we used a converter at the end to solder the wires with it and directly insert those in the bread board.
Row 1 to row 4 are attached to Pin 0 to pin3 of port 3 and similarly the pin 4 to pin 6 are used for columns last pin is not used of port 3.
Key scanning is quite simple the row and columns when made short through the keypad enables a single key and display it on the LCD.
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