Digital Expression Via Harmonica

There is a good chance you clicked on this article with a mouse, trackball, trackpad, or tapped with your finger. Our hands are how most of us interact with the digital world, but that isn’t an option for everyone, and [Shu Takahashi] wants to give them a new outlet to express themselves. Some folks who cannot use their hands will be able to use the Magpie MIDI, which acts as a keyboard, mouse, MIDI device, and eventually, a game controller. This universal Human Interface Device (HID) differs from a mouth-operated joystick because it has air pressure sensors instead of buttons. The sensors can recognize the difference between exhalation and inhalation, so the thirteen ports can be neutral, positive, or negative, which is like having twenty-six discrete buttons.

The harmonica mounts on an analog X-Y joystick to move a mouse pointer or manipulate MIDI sound like a whammy bar. [Shu] knows that a standard harmonica has ten ports, but he picked thirteen because all twenty-six letters are accessible by a puff or sip in keyboard mode. The inputs outnumber the Arduino Leonardo’s analog inputs, so there is a multiplexor to read all of them. There was not enough time to get an Arduino with enough native ports, like a Teensy, with HID support baked in. Most of the structure is 3D printed, so parts will be replaceable and maybe even customizable.

Even with two working hands, we like to exercise different hardware, but the harmonica is a nifty tool to have attached to your computer.

11 thoughts on “Digital Expression Via Harmonica

  1. Dang, that is clever! But every time I read an article like this one, it sends me down a rabbit hole of researching and pondering the possibilities for using it. Hackaday is a pox on my productivity.

  2. Natty. I’m curious how they can be cleaned through. Some of the reason why sip-puff controls are often very expensive is the need for in-line PTFE filters. These come with removable tubing that can be flushed through. It’s an important consideration, especially so in these Covid-19 days. Perhaps these can be disassembled by the user and thoroughly cleaned?

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