Wednesday, June 8, 2016

GyroMouse Preview

So, I'm putting together another "Device". I make them occasionally. Some of them even work.

GyroMouse Prototype.
MPU6040 IMU Attached to Raspberry Pi Model A+

While I'm waiting for most of the specific hardware pieces to turn up from all over the internet, I've been slapping together prototype parts and getting the software at least vaguely right. I find that helps.

One goal for this new device is to be compact, so I'm going to use a Raspberry Pi Zero (which I believe is in the post. They're a little hard to get.) So compact that the entire machine can be wrist-mounted, smart-watch style.

And in fact, that's working out fairly well. The Pi Zero is only 70x30mm, 1.5" screens are about 30mm vertical. I have a very specific 80x40x20mm lozenge-shaped space that I need to fit, for reasons which will become obvious in later posts.

You can fit a whole 512mb / 1Ghz processor with GPU hardware in that space, with enough battery to run for hours. WiFi dongles are mostly just connector now.

What's hard to fit is any kind of human-friendly input device. The screen is so small that "touchscreen" tech would be ludicrous. It might be nice to turn the entire surfacebeyond the screen into a capacitive touchpad, but there's no ready sources for such a module, and I'm trying to use Adafruit-level commodity pieces.

Assuming I've got a small linux machine with X11 on my wrist, what's the best way of using that device? Well, mouse is probably still it, in terns of compatibility with existing software. With a mouse you can run an on-screen-keyboard if you have to. It will do everything, if badly.

So to fit something like a mouse in the space available, I've written a little program which listens to a MPU6040 Intertial Management Unit and interprets it's movements as mouse commands. Gyro rotations in X and Y move the mouse cursor, and "taps" on the device (detected by the accellerometer) are interpreted as mouse clicks. At least for today.

To control a tiny computer you need a tiny input device!

 As of an hour ago, it works. I had to go through four "i2c" libraries to find one that's stable under node.js, ('i2c-bus" is the one you want.) I'm not happy with the CPU usage to be honest, but it does actually work. I can push the mouse cursor around the desktop by tilting the sensor various ways, and even click on things with considerable difficulty.

Size comparison against my usual mouse.

I'm using Gyros for movement and Acceleration for mouse 'clicks', which is quite different from the "accellerometer" mice I've seen before. The difference there is, accelerators measure "tilt" due to gravity. So in those cases, the mouse cursor acts a lot like the little steel ball in those closed maze puzzle games, rolling around on a flat surface.

Sounds like a good idea at first, but you're asking people to keep the device perfectly flat in order to keep the mouse still. Most people don't intuitively know where "perfectly flat" is.

Gyros sense relative rotational motion. The turning to and fro of an object. Gyros are the most important part of a Quadcopter's IMU, which I know well.

Funny thing, I did a search and I don't think anyone else has built a gyromouse. They all go for accellerometer-mice. Well; technically the Wii-mote, but it also uses the IR lights, so it's a hybrid.

Is this the world's only Gyromouse?
To be honest, I haven't really looked that hard.

GyroMouse works off the relative turning motion of the chip to simulate the movement of a mouse. And it detects the "freefall" moment of when you tap the device downwards as a mouse click. It feels horrible, needs extensive tuning, but it functions. I can click on menus. I might be able to extend it to detects 'taps' in various axes, so whacking this particular device from the sides might end up working as other buttons, or maybe the scroll wheel.

I think that's called a "kinetic interface". Similar, although slightly different to "percussive maintenance". But that's kind of the point here... to experiment with what happens when you make a computer aware of it's physical state, and smart enough to respond and adapt.

If you want to be mean, you can denigrate the whole thing as an over-complicated Wii-Mote. And you'd be right. It's a Wii-Mote that doesn't need the Wii. It does everything all by itself.

Right now this is still at proof of concept stage, though later on I'll release the code when it's not quite as embarrassing, and the real hardware has arrived. Leave a comment if you're interested.


  1. The LG magic remote control is like your gyro mouse, but oriented to smart tvs.

  2. Nice post ,good information .i like this smart things

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