A 16 key pad would have 4 columns by 4 rows ... of the keypad Next is a project example, where the Arduino is instructed to do something based on a correct key (secret number) being entered into the ...

Everything else under the hood is pretty standard, with a pair of Arduino Pro Micros ... but still miss the num pad? Why not build one to match your keyboard?

Instead of fixing the problem, [Maximilian] made it worse by interfacing a rotary phone as a num pad ... as a USB keyboard. This is a great opportunity to ditch the Arduino and use the V-USB ...