Generally, we interface a single button, switch, or key with a microcontroller using a single GPIO pin. However, if we want to interface several 9 or 12, or 16 keys, then it requires various microcontroller GPIO pins. To save some of the microcontroller GPIO pins, we can utilize a 4x4 keypad module. This module includes keys that are arranged within rows & columns. So, if we desire to interface 16 keys with a microcontroller then we need 16 GPIO pins although if we utilize a 4x4 matrix … [Read more...]