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Anti-Ghosting Multi-touch

Papier Logik will be at Fab14+, France 11-22 July 2018
 
Project Sumarry: 
A 12*12 paper-based multi-touch interface with Integrated Anti-Ghosting diodes for Custom Digital Music Control and more
Project Cathegory: 
Digital Music Instrument

The LoganBoard is a collaboration with Logan K. motivated by solving the usual ghosting issues appearing in many industrial keyboards as well as when building simple Force sensors arrays. 

1 - The problem to solve: prevent ghosting in a paper array

A simple matrix design of vertical bands (each connected to independant Digital Inputs  fed sequentially by the voltag input) 

 

2 - The solution proposed: insert x*y Leds or diodes to the design

To prevent the current back-flow that disturbs data read and generates ghosting, it takes to instert properly diodes or leds (Add Ref) that will block the current through connected loops in the array.

This can be a long work , as for a matrix of x rows and y columns, x * y diodes must be used, and the paper bands must be turned to squares of the matrix' pixel size.  Such microelecrtonic componenet cannot yet be produced but are widely available on the market.

We then started from an existing matrix composed of rows bands sticked onto a support and columns bands placed on top in a secnonf soft layer. We remove this top-layer, and cut  the rows bands so that this layer turns into a set of conductive x * y pixels, with ideally sufficient space to insert the diodes.

We explored 3 types design solutions through various gradual attempts: in the first solutions we used led for a 3 * 3 matrix as a proof of concept.

We then modified the design so as to have all diodes localized in a row at the bottom of each collumns for faster assembling.

We finally built a 12 * 12 matrix with 2cm pixel's size and 0.3 mm to fit  3mm*1mm diodes between pixels, with the minus pôle heading towards the voltage divider resistors. 

IMPORTANT: For uniform results, we always used the same diodes or Leds for a given matrix) 

 

3 - Mapping Application: MIDI Music Board

An .ino File was produced by default to habe the borad directly mapped to be plug and play and communicate with MIDI applications on most computers cappable of handling usb hardware and the Teensy application for Serial MIDI Communication.

The mapping is based on Logan's tuning. The original tuning was for a twice bigger array, but the Teensy we used (3.2) could not handle so many I/O withtout adding more electronics.

We also developped some Presets for the MAPS software that enables to reconfigure the mapping on Air and used the board as a more global computer controller.