Methods and devices for determining touch locations on a touch-sensitive surface

Abstract

A method is performed at a touch sensing system that includes a two-dimensional capacitive sense array. The process measures the capacitance of the capacitive sensors, and identifies a first sensor whose measured capacitance is a local peak. The local peak is within a local rectangular array. The process computes column sums for each column of the rectangular array and determines whether to apply a smoothing algorithm. When the smoothing algorithm is not applied, the process computes an x-coordinate of a touch using a plurality of the column sums. When applying the smoothing algorithm, the process computes the x-coordinate of the touch as an average of two x-coordinate calculations. Each of the two x-coordinate calculations conditionally performs a horizontal shift of the local rectangular array based on comparing the peak measured capacitance to an adjacent measured capacitance and computes a respective x-coordinate using a respective plurality of the column sums.