This 28×28 matrix was used in the rSkin project to visualize pressure and location of pressure applied to a rectangularthat was wrapped around a robot arm.
rSkin progress blog >> http://www.plusea.at/?page_id=2259
Arduino/Teensy code >> https://github.com/iandanforth/rSkin/tree/master/teensy
Processing code >> https://github.com/iandanforth/rSkin/tree/master/vis
28 Rows and columns