Matt again.
When I'm not dedicating inordinate amounts of time to electronics for high altitude photography (similar to this) I'm working to test and better our touch pad interface. With Micheal. And it is going slow because I lack life experience with sewing and seaming. What we've found is a number of issues with the touchpad.
The most basic is that it doesn't like us. Our initial concern with unintended button presses has been brought to a painful forefront. Thereabouts of the only gesture that could possibly reliably work right now is slapping your hand down on your wrist. What tends to happen is that in the course of touching the pad hard enough to make a contact, a number of other contacts are also made. This leads to massive squares and square shaped entities of contact, which are useless from a recognition point of view. We expected some unintended presses, but also expected them to be confined to a small region. The current '1 press leads to chaos' mechanism isn't going to work.
In all likelyhood, this is caused by the separator material. We used felt as a compromise between pliability (for ease of making contacts) and strength, for keeping contacts broken. This doesn't seem to have worked out too well. We're going to try adding a plastic backing to reinforce the felt, ignoring compressibility in favor of usefulness, and we'll see where that takes us.
If given more time, I think the main thing that we should look at would be using a better separator. What I suspect we need is something more akin to a soft foam- like you'd get with certain pillows or foam pads. Something that basically acts as more of a spring, but with low tension- ie, can be easily compressed, but will keep enough distance that creases in the outer fabric layer won't lead to unintentional contact.
Ultimately, I suspect we're looking at a tradeoff between "pressure required to activate" and "accuracy of input". With the added bonus of "pain to work with". Some initial experiments with foam from hobby lobby reveal that cutting it to thin enough slices is a precise art, for which I am like 3 year old in an art museum. Getting holes in the separator is also rather difficult, the only reliable method I've had so far is to take a soldering iron to it and burn holes through it, hoping it doesn't catch fire or spew forth toxic fumes.
Other things to think about might just be the removal of a gesture system all together, in favor of an actual button pad. I don't believe a soldier is going to have much luck remembering more then five or so gestures; developing an actual special purpose key pad, rather then a touch pad, would probably be more successful, as it can be done with far fewer buttons, and thus without the need for multiplexing IO that led to our mass of touch detections.
Next week Micheal is up for chatting, until then we'll continue playing around with the prototype to try and get it closer to working. Somewhere in this set of things is getting the Bluetooth code integrated into Adams gesture recognition app, we'll see how far we can get with all these things.
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