Patent attributes
An apparatus (73) for processing signals from a touch panel (10) is described. The touch panel (10) includes a layer of piezoelectric material (16) disposed between a number of sensing electrodes (14, 20) and at least one common electrode (15). The apparatus (73) includes a capacitive touch controller (69) for connection to the sensing electrodes (14, 20). The apparatus (73) also includes a switch network (74) including a number of inputs for connection to some or all of the sensing electrodes (14, 20), and an output connected to system ground or a common mode voltage (VCM). The apparatus (73) also includes a second circuit (24, 44) for connection to the at least one common electrode (15) and configured to generate, based on signals received from the at least one common electrode, a second pressure signal (30) indicative of a total pressure applied to the touch panel (10). The apparatus (73) also includes a controller (25) configured to control the switch network (74) to couple any connected sensing electrodes (14, 20) to system ground or the common mode voltage (VCM) during a pressure measurement period, and to determine an estimate of the total pressure based on the second pressure signal during the pressure measurement period.
