Push the button

The keyboard, one of the most commonly used hardware. We take it all for granted yet only few know what is going on behind all these keys.
This post will briefly explain what is going on in that magical thing we call a keyboard.

Most keyboards have between 80 and 110 keys. These keys allow us to type documents, open menus, play games, surf to whichever wicked website we have in mind, etc…
This is the part you already know (well I hope at least, if not, please enlighten me how you got on this blog? I think that will be a fascinating story :D)

Now inside the keyboard, as with many devices, there is a miniature computer. It has it’s own tiny CPU and a circuit board which allows data to flow from the computer to the keyboard and the other way around.
The biggest part of the circuitry of the keyboard is the key matrix. This is a grid of circuits underneath your keys.
Each of these circuits are broken, this means that you hit a switch every time you press a button.
This will complete the circuit for a moment and will allow an amount of current to run through it.
If you so happen to press and hold a key, the processor of the keyboard will recognize this as pressing a key repeatedly.

Now, when the circuit is closed, the processor will compare the location of the closed circuit on the key matrix to the character map in its ROM (Read Only Memory, remember? ;-)).
This character map tells the position of each key in the matrix and what each keystroke represents.

There is, however, one exception when it comes to keyboards. They do not all use small switches as previously explained. There is also a technology called “Capacitive” switches, these are considered non mechanical, since they do not complete a circuit, physically at least.
What happens here is, that a current flows constantly through the key matrix. Each key has a small plate attached to its bottom. When you press a key, it moves this plate closer to a plate below, which causes the amount of current flowing through to change within the matrix.
What happens next is similar as before, you hit a key, the processor recognizes the keystroke, compares it with the character mapping in the ROM and off we go :).

In short.. how the keyboard works ;-)..

(and yes I ripped a few images from the internet again, I’m sorry :()

How’s this for a keyboard


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