Tutorial parts: 1 matrix | 2 controller (coming soon) | ...
Update (May 2016): check out the Russian translation: Как сделать клавиатуру — Матрица!
This will be the first and hopefully not the last post in the keyboard series. I'm hoping to make this a keyboard building tutorial from the ground up. Today I'll cover digital I/O and keyboard matrices. Equip yourself with some basic knowledge of electronics from school and let's get started.