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The Bit

A tongue IO device

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The goal of this project is to create a new input device that allows the user to control a mouse with a small sensor placed on the roof of the mouth. I imagine this HCI will benefit those who have poor/nonexistent use of their fingers or those who need to use their hands elsewhere at the same time they control a mouse.

I have assembled a functional prototype that includes a bite force sensor to activate tracking (with light pressure) and to detect clicks (firm pressure). All design details will be made available. My goal is 100% open source and open hardware.

Initially I  was working to reverse engineer the interface for the optical trackpad/joystick/navigation buttons used on a number of blackberry phones. 

These modules are essentially tiny cameras with built in logic to determine the frame-by-frame differences of the surface being tracked, usually a fingertip, but a tongue should work as well. 

I purchased modules from two different phone models, but they turned out to use completely different internal tracking modules.

While researching these sensors I found a new sensor made by PixArt Imaging intended for surface tracking applications. (It is also used as the filament tracker on new Prusa printers)

Mouse_Demo_14.ino

Arduino sketch for the Teensy - emulates mouse movement and clicks. Serial debug output.

ino - 6.75 kB - 08/27/2018 at 12:18

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  • Adjustable bite force threshold

    oneohm08/27/2018 at 13:48 0 comments

    A single turn 10K potentiometer is used in combination with the bite force sensor to create an adjustable voltage divider. This will probably be replaced with a fixed value resistor eventually, but it was helpful to have an adjustable value during testing. Here you can see the potentiometer zip tied to the back of the Teensy 3.1.

  • Teensy 3.1 Configuration

    oneohm08/27/2018 at 13:39 0 comments

    A Teensy 3.1 microcontroller board is used to interface the sensor and emulate a USB mouse. 4.7K resistors have been added to the i2c pins.

    Signals:
    yellow: 3.3V
    green: GND
    blue: Force sensor analog value
    white: SCLK
    purple: SDA

  • Bite force sensor

    oneohm08/27/2018 at 13:29 0 comments

    I added a conductive rubber pressure sensor to measure bite force.

    This allows tracking to be enabled with light bite force, and registers clicks with a stronger bite. 

    The force sensor is connected to the 10K potentiometer to create an adjustable voltage divider that connects to an analog input pin on the Teensy 3.1.

  • Packaging the sensor

    oneohm08/27/2018 at 13:22 0 comments

    I modified an adult sized pacifier to hold the tracking sensor. The sensor is configured to use just 3.3V, GND, SDA, and SCLK signals.

  • Reverse Engineering

    oneohm08/27/2018 at 13:14 0 comments

    Disassembled blackberry module:

    The desoldered tracking chip:

    Early attempt at working out the pinout:

  • Initial development

    oneohm08/27/2018 at 13:07 0 comments

    Initially I  was working to reverse engineer the interface for the optical trackpad/joystick/navigation buttons used on a number of blackberry phones. 

    These modules are essentially tiny cameras with built in logic to determine the frame-by-frame differences of the surface being tracked, usually a fingertip, but a tongue should work as well. 

    I purchased modules from two different phone models, but they turned out to use completely different internal tracking modules.

View all 6 project logs

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Discussions

Kris Jones wrote 09/12/2018 at 16:50 point

Where did you order the Pixart sensors? I have tried to find a distributor, but the only place that had them in stock does not ship samples to the US. 

  Are you sure? yes | no

Curt White wrote 08/27/2018 at 12:30 point

how to you get it to stay put in the mouth?

  Are you sure? yes | no

AnnonAB wrote 4 days ago point

They generally stay relatively comfortably so in the mouth unless you were to literally spit the dummy.. Babies, ravers and abdls/ddlgs don't have any issues. :P

You could make a pacifier clip to house the uC and run the wires up to the pacifier to keep everything neat and contained, maybe with stiff wire or a swing arm on the wheelchair to keep it near face height to accommodate those who can't get it back in themselves..

Of course, there is always this option https://images-na.ssl-images-amazon.com/images/I/810v1bXOdKL._SX355_.jpg (warning: kink related, but worksafe).

The majority of the adult pacifiers can be pulled apart, you usually don't need to hacksaw off the button, the button can instead be drilled, wires fed through and then the sensors soldered on the other side, allowing it to be put back and hold everything in place.

I know a little too much about these, I guess you could say I'm within the target audience for adult pacis >.> sorry (posting with an alt).

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zakqwy wrote 04/25/2018 at 02:29 point

neat concept. I've got a pile of those sensors around, looking forward to seeing how well you can get em to work!

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