Description: This is the VKey Voltage Keypad, a simple board that adds a keypad to your microcontroller project without using multiple I/O pins. This keypad has 12 pushbutton switches in a 3x4 array. The VKey operates by outputing an analog voltage to encode which key has been pressed, which can be read by an analog to digital converter on a microcontroller on a single input pin. Traditional digital keypad interfacing techniques can require a large number of digital I/O lines. On a small controller, there may not be many I/O pins left for other tasks. The VKey operates at a voltage of 3.3-5.5V and features a dual opamp which is used as a current source and buffer amplifier. [GitHub][1] (Design Files) [GitHub][2] (Library) Sparkfun link:https://www.sparkfun.com/products/12080 ![enter image description here][3] [1]: https://github.com/sparkfun/VKey_Voltage_Keypad/tree/V_H1.0_L1.0.2 [2]: https://github.com/sparkfun/SparkFun_VKey_Voltage_Keypad_Arduino_Library/tree/V_1.0.2 [3]: /editor/20151231/5684cf3e7075d.png