Welcome to the first installment of Inputs of Interest. In this column, we’re going to take a look at various input devices and methods, discuss their merits, give their downsides a rundown, and pontificate about the possibilities they present for hackers. I’ll leave it open to the possibility of spotlighting one particular device (because I already have one in mind), but most often the column will focus on input concepts.
Some inputs are built for having fun. Some are ultra-specific shortcuts designed to do work. Others are assistive devices for people with low mobility. And many inputs blur the lines between these three ideas. This time on Inputs of Interest, we’re going to chew on the idea of oral inputs — those driven by the user’s tongue, teeth, or both.
Unless you’ve recently bitten it, burned it, or had it pierced, you probably don’t think much about your tongue. But the tongue is a strong, multi-muscled organ that rarely gets tired. It’s connected to the brain by a cranial nerve, and usually remains undamaged in people who are paralyzed from the neck down. This makes it a viable input-driving option for almost everyone, regardless of ability. And yet, tongues and mouths in general seem to be under-utilized as input appendages.
Ideally, any input device should be affordable and/or open source, regardless of the driving appendage. Whether the user is otherwise able-bodied or isn’t, there’s no reason the device shouldn’t be as useful and beautiful as possible.
Mouth-based interfaces could be incredibly useful for everyone, and not just as assistive technology for the alternatively-abled. But much like any other type of input device, their utility depends on a few factors, starting with the number of controls. Too little control, and there’s no point in teaching the tongue new tricks.
But too many controls will get out of hand fast. Wiring up a second 108-key board as a computer macro menu that’s large enough to rival the Cheesecake Factory’s is nice idea, but only if you can keep track of and find serious utility in that many shortcuts.
Whatever the controls are, they should ideally work across platforms and objects — i.e. the same device could be used to drive a wheelchair to a desk, and then switch over to interface with the computer sitting on the desk.
Old Stuff: Sip and Puff
Of course, too little control is better than none at all. I would be remiss if I didn’t acknowledge what is probably the oldest oral-based assistive device out there: the sip-and-puff interface. Using a single straw, users are able to control different inputs by sipping, or inhaling through the straw, and other inputs by puffing, or exhaling through the straw. Sip-and-puff has been around for many decades and is still used to drive everything from wheelchairs to sailboats to touch screens.
Depending on the device, sip-and-puff doesn’t have to be complicated or even wired. TubusOne is a low-tech implementation that acts like an extendable mouth finger. Huff a little puff of air, and a slim digit with a conductive fabric tip pops out to help you navigate any touch screen, anywhere.
The biggest downsides to commercial sip-and-puff devices is that they don’t offer much fine control, and they still cost hundreds of dollars after all this time. Aside from the expense, the interface is anything but discreet. Unless it looks super cool, we’d venture to guess that a fair number of able-bodied people who would use an oral input device would prefer it be hidden, if at all possible.
Is That a Mouse in Your Mouth?
You may remember Pallette from a few years back, because this Bluetooth mouth mouse won $1000 in the assistive technologies design challenge of the 2016 Hackaday Prize.
Pallette is built on a custom-molded retainer that sits against the upper teeth like a mouth guard. An infrared sensor reads the tongue’s position to move a cursor accordingly, and a microphone translates tongue taps into clicks.
I love that Pallette is so vehemently open source. The creators built a website that has detailed instructions for building your own for around $200.
Pallette ticks many boxen for me. It’s discreet — the thing fits entirely within your mouth, with no wires and no headset. The only downside is that it seems like a lot to pack inside of a small mouth.
Though it’s not open-source, here’s a controller that minimizes the mouth component BOM down to one item: a small magnetic tongue stud. The user wears a headset full of sensors that detect tongue movements through changes in the magnetic field of the stud. The big benefit here is that since there is so little hardware inside the mouth, it doesn’t get in the way of speaking. The system can also be switched off with a long press of the tongue, and left in place while eating. Here’s a video of it in action.
Safe, Sanitary, and Scalable
If these things are going to catch on in some form, they need to be safe, sanitary, and scalable. If ‘wireless’ means there’s a battery in your mouth, you want to be careful. Pallette uses a silver oxide battery that has many advantages over lithium-ion, not the least of which is a drastically lower flammability rating.
If we imagine these assistive inputs in the workplace, there are more things to consider. With Pallette, every worker would need to have a custom-fit mouth guard. Thermoplastic isn’t that expensive, but it would add up.
If the electronics live in a standardized enclosure, then you have a one-size-fits-all solution that’s scalable for mass production. The Bit, another Hackaday.io project, satisfies that condition nicely. All the electronic goodies are cleverly contained inside an adult pacifier. At first glance I thought it was molded acrylic, but this is an off-the-shelf pacifier. [oneohm] used a pair of hacked snap ring pliers to spread the opening wide, and then shoved the board in there.
The beta prototype runs on an ATmega32u4 breakout and uses an optical tracking sensor to keep tabs on the tongue. There’s also a time of flight sensor, because why not track the tongue in the z-direction, too? There’s a pair of conductive rubber force sensors to translate gentle tongue pressure into up and down scroll commands, and they register full-on chomps as clicks. As you can see in the picture, [oneohm] played around with triangulating the force sensors for joystick control.
Ease of Use
All of these devices have their merits, but there’s one thing they haven’t considered: the starting and stopping conditions. How are you gonna get this device in your mouth by yourself if you’re paralyzed from the neck down? The project that inspired this installment, Assistive Tongue-Operated Mouse (ATOM), handles that problem elegantly. When not in use, the retainer attaches magnetically to an acrylic stand, but it could just as easily link to something similar mounted on a wheelchair.
ATOM can be made for under $100, minus the base. The brain is an Arduino Pro Micro, and the main control is the pointing stick from a laptop keyboard that your tongue uses as a D-pad. I like that ATOM gets your teeth involved, too — there’s a pair of momentaries you can munch with your molars to register left and right clicks. [Ben Krasnow] made one kind of like it a few years back.
Something to Chew On
No matter who the user is, mouth inputs should be safe to use. Ideally, they should be cheap to make and easy to use from start to finish. In a perfect world, they would be completely hidden from view and small enough to allow speaking or even eating. That’s clearly a tall order, but it’s one worth working on. If you’ve got any favorite mouth inputs, let us know!
(Full disclosure: I’ve never used a tongue- or mouth-controlled input, but I totally would. And after giving them so much consideration, I may have to take a shot at making my own. It would be another way to do more while keeping my hands on the keyboard, and I’m all about that.)