Pixelated mutual capacitance sensing for water detection

Abstract

A pixelated mutual capacitance sensing configuration to detect the presence of floating water is disclosed. An integrated touch screen can be configured in a checkerboard arrangement of alternating drive pixels and sense pixels, where each drive or sense pixel can include a plurality of sub-pixels. The sense pixels can include sense sub-pixels surrounded by ground sub-pixels to reduce the baseline mutual capacitance between the drive and sense pixels. Stimulated drive pixels can capacitively couple onto the sense sub-pixels of the sense pixel, forming a baseline (no touch) mutual capacitance between the drive pixels and the sense sub-pixels. The presence of grounded objects shunts some charge to ground and reduces the mutual capacitance, while floating water provides and additional parallel mutual capacitance path that increases the mutual capacitance. Floating water can be distinguished from a grounded touch based on the direction of the change in mutual capacitance.