The keypad is widely used in many devices such as door lock, ATM, calculator…
Pinout
Keypad pins are divided into two groups: row and column.
Keypad 3×4 has 7 pins: 4 row-pins (R1, R2, R3, R4) and 3 column-pin (C1, C2, C3).
Keypad 4×4 has 8 pins: 4 row-pins (R1, R2, R3, R4) and 4 column-pin (C1, C2, C3, C4).
