In the last blog I showed a slide-pot HID mouse. but it was not truly providing absolute mouse position, which is needed for the finger touch version. It was using an arduino to try and keep track of where the mouse was in an absolute sense and using relative mouse movement to get to where the pot voltages were demanding. It was a bit glitchy and could lose track of its position and it was still too sensitive to acceleration - so I spent a lot of time to try and smooth he system out with software, checking for glitches and filtering plus editing the mouse configuration parameters for acceleration etc. The HID device did not have as many parameters to edit as a proper mouse, so it still ended up less than satisfactory on the Raspberry Pi, although it worked quite well on a PC.

Eventually I discovered the absmouse library programmed by Johnathan Edgecombe, which took care of the absolute coordinate and acceleration issues, and my filters took care of the glitches. I don't know how I missed this library earlier - probably I believed all the stories about how Linux couldn't do absolute mouse moves, and stopped looking.

Here is a quick video showing the slide-pot mouse editing a photograph I took this winter:

It is the first "artwork" of the PiCassoTizer system - its an awful long way from a Picasso, but even baby steps can be interesting.

The pieces are starting to come together. There is still some software to do to get the trigonometry right, but most of the tricky stuff is well on its way. I am still waiting for parts to make a complete system, which is a little worrisome, but sometimes that is how it goes. Maybe I can work on some of the 3D printed parts and adapt the geometry when the parts come in.


Relevant links:

PiCasso Design Challenge


PiCassoTizer - Introduction - blog 1

PiCassoTizer - Electronic Parts - Blog 2

PiCassoTizer - Finger Detection Image Processing - Blog 3

PiCassoTizer - Absolute Mouse Position - HID Simulation - Blog 4

PiCassoTizer - The Snowman Smiles - Blog 5