The SparkFun VKey Voltage Keypad is a 3×4 pushbutton keypad that uses just a single analog input pin on your microcontroller. Instead of requiring multiple digital I/O lines like traditional keypads, the VKey outputs a unique analog voltage for each key press, which your microcontroller's ADC reads on one pin.

The board uses a dual op-amp configured as a current source and buffer amplifier to generate clean, distinct voltage levels for each of the 12 keys. It operates from 3.3V to 5.5V, making it compatible with most microcontrollers.

Key Features

• Single Analog Pin Interface – Uses just one ADC input for all 12 keys
• 3×4 Keypad Layout – 12 pushbutton switches
• 3.3V–5.5V Operation – Compatible with 3.3V and 5V microcontrollers
• Dual Op-Amp Design – Clean voltage output with LMV358 current source and buffer
• Arduino Library Available – Ready-to-use software support

Ideal For

• Projects with limited I/O pins
• User input on small microcontrollers
• Numeric entry and menu navigation
• Security keypads and access control

Package Contents

• 1× VKey Voltage Keypad PCB (SMD components pre-assembled)
• 12× PTH tactile switches (loose, soldering required)

Resources

• SparkFun VKey Hookup Guide
• Arduino Library (GitHub)
• Schematic (PDF)
• LMV358 Datasheet (PDF)