How to turn Piano toy into MIDI keyboard (using Arduino/Atmega)

Recently I've recovered a broken Casio SA-47 piano toy:

Pic1: Keyboard

What a great opportunity to experiment I thought! I always wanted to make my own midi device and here was a chance. So I decided to make a midi keyboard.

Below is the video of the final result...

For those interested there is a second part of the project here where we add Velocity and After touch to the keyboard.

>>> UPDATE: Thanks for your interest! MIDI Kit available here! <<<