Wednesday, March 23, 2011

AT Keyboard Signal Analysis

I'm a programmer and am surrounded by people that love to bang on their keyboards all day. In fact, I bet you're one of them! Even if you're not, you probably just finished typing 'AT Keyboard', 'AT Keyboard Signal', 'AT Keyboard Circuit' or something of the sort into your favorite search engine. Gotcha didn't I? Or, maybe not, w ho knows! Millions of people are banging on these things each day. Keyboards never complain and all they do it take a pounding from you, day after day after day., These poor things, they're pushed around, shoved around, slid across the table. Sometimes they are banged with one hand, sometimes with two! They wait around patiently, hoping for a taste of your table scraps, or a sip of that coffee you just spilled. It's a sad and tragic life, I know. Despite the daily abuse, these keyboards look beyond our cruelties and deliver byte after byte, asking nothing in return.

Have you ever asked yourself, what makes this keyboard tick? How does all my finger twiddling make it down the line and into that box over there? Take a few minutes to think about it. Once you're done thinking about it, take a look at these two signals:

This is a snapshot of the raw signal that is transmitted down the data line, when the spacebar key is pressed.

This is the signal transmitted down the data line when the enter key is pressed.

I will leave you with two questions to think about until I finish up this post:

1) Is keyboard / PC communications one way or two way?
2) How are the key presses encoded?

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