Who knows what you’ll find in a second-hand shop? [Zeal] found some old keyboards made to fit early Alcatel phones from the year 2000 or so. They looked good but, of course, had no documentation. He’s made two videos about his adventure, and you can see them below.

The connector was a cellphone-style phone jack that must carry power and some sort of serial data. Inside, there wasn’t much other than a major chip and a membrane keyboard. There were a few small support chips and components, too.

This is a natural job for a logic analyzer. Sure enough, pressing a key showed some output on the logic analyzer. The device only outputs data, and so, in part 2, [Zeal] adds it to his single-board Z-80 computer.

It makes a cute package, but it did take some level shifting to get the 5V logic to play nice with the lower-voltage keyboard. He used a processor to provide protocol translation, although it looks like you could have easily handled the whole thing in the host computer software if you had wanted to do so.

Truthfully, there isn’t much chance you are going to find this exact keyboard. However, the process of opening a strange device and reverse engineering what it is all about is classic.

Don’t have a logic analyzer? A scope might have been usable for this, but you can also build one for very little these days. Using a PS/2 keyboard isn’t really easier, by the way, it is just well-documented.