High precision study of K+- --> 3pi+- decays by NA48/2

Preliminary results of study of $K^\pm\to3\pi^\pm$ decays by the NA48/2 experiment at CERN SPS are presented. They include a precise measurement of the direct CP violating charge asymmetry of Dalitz plot linear slope parameters $A_g=(g^+-g^-)/(g^++g^-)$, and a measurement of the Dalitz plot slope parameters $(g,h,k)$ themselves. Due to the design of the experiment, and a large data set collected, unprecedented precisions were achieved.