Adafruit Silicone Elastomer 4×4 Button Keypad – Adafruit 1616, The Adafruit Trellis Monochrome Driver PCB is the perfect partner for Adafruit’s 4 x 4 elastomer keypad to save you the time needed to design a suitable PCB. Each Trellis PCB has a 4 x 4 matrix of switch contacts that exactly match the elastomer keypad and each contact has pads for a 3mm LED. The board uses an I2C controlled keypad and LED matrix chip to handle the details, you will need to supply a microcontroller such as the Arduino Uno or Orangepip to tell it what LEDs to light and to read the keypresses.Each board has 3 x I2C address jumpers giving you a maximum of 8 x keypads on one I2C bus for a total of 128 x buttons and 128 x LEDs. When you are tiling these boards they share all external connections including power, ground, interrupt and I2C pins. Each button has room for a 3mm LED so that you can illuminate just those keys that are active in your project. You don’t have to add LEDs, but it does look pretty cool; diffused LEDs are the best.Supplied as a fully assembled and tested keypad and LED driver board only, it does not come with the elastomer keypad, a microcontroller, LEDs or cable. Adafruit provide an open source Arduino library and example code plus a free tutorial to help get you started. Adafruit 1616 Trellis Monochrome Driver PCB for 4×4 Keypad & 3mm LEDs