chording bluetooth keyboard

Wearable computing is much older than Google glass, and even head mounted displays were around for a while. Personally, I’m looking forward to affordable devices of that type. The display seems to be a very good solution, while voice entry can be awkward. The Hak5 podcast aired an episode last year about a guy that has walked around with a head mounted display and a computer in his backpack for a long time. While the display is certainly cool, what was most intriguing to me was the keyboard. He uses a one hand device with key press combinations that he can operate while walking around.

I didn’t find his exact model when searching the Internet, and while there are some devices around in this category, the selection is very sparse. They are called chorded keyboards, and were first introduced in 1968 at what is often called “The Mother of All Demos“. Then I found out that there is an open standard for this sort of thing. It’s called GKOS and stands for Global Keyboard Open Standard. They experiment in lots of different directions, but no commercial product seems to have come out of this so far. Amongst the different experiments, there is an Arduino project to build a GKOS keyboard, but I considered an Arduino with custom buttons too bulky for practical use.

A while ago, I ordered a cheap 6-key HID device that I wanted to use to try GKOS myself. I tried a while with key remapping but to no avail. And I strongly suspected, the device could not handle key combinations at all.

Last week, I somehow remembered my failed past attempts, and thought that a bluetooth device would be cool. I quickly confirmed that all the DIY bluetooth modules that I had were not capable of HID but only UART. Then I found a simple to use bluetooth HID module, that was apparently released just two months ago. What a coincidence!

The first test with the GKOS Arduino code on a breadboard was successful. So, I disassembled the USB device, and re-soldered the buttons to an AtMega8 and added a lithium battery from a defunct tiny quadrocopter.  But after I soldered everything together, only some keys would work. I was sure, an AtMega8 would be able to handle this simple task with ease, but I had to use an Atmega328 to make it work. It costs a few bucks more, but much less than the time for finding out what the problem with the AtMega8 was. I didn’t inspect the code throughly enough yet, but maybe the AtMega8 is just missing some hardware interrupts.

So far, I’m very slow at typing, and I have to peek at the cheat sheet for most characters, but with a bit of training that should improve. My prototype works well for two handed operation, but I think one handed operation would be the way to go, although I don’t know if GKOS is really suited for that.

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