4x4 Key click mikroBUS™ A Click accessory module for use with MikroElektronika mikroBUS™ microcontroller development boards. The 4x4 Key click has a 16-button keypad which allows multiple keys to be pressed simultaneously. The status of the switches is read by a pair of 8-bit parallel-in serial-out shift registers and silk screened legends on the PCB to identify each of the pushbutton switches. Communications with the target microcontroller are via an SPI mikroBUS™ interface and the board requires a 3.3 or 5V power supply.