Force input localisation

A device comprising:

• a piezoelectric sensor comprising a layer of piezoelectric material disposed between a plurality of sensing electrodes and at least one counter electrode, wherein the plurality of sensing electrodes are arranged to form one or more active regions, each active region of the one or more active regions comprising:
• a group of one or more primary sensing electrodes of the plurality of sensing electrodes, the group of one or more primary sensing electrodes arranged with overlying indicia defined on a surface of the device so as to define one or more user input controls;
• a group of one or more secondary sensing electrodes of the plurality of sensing electrodes, the group of one or more secondary sensing electrodes surrounding the group of one or more primary sensing electrodes, wherein the group of one or more secondary sensing electrodes do not correspond directly to user input controls, and wherein the group of one or more secondary sensing electrodes have no corresponding indicia defining user input controls;
• and
• a perimeter, the perimeter being a locus of points separating the group of one or more primary sensing electrodes from the group of one or more secondary sensing electrodes, such that the group of one or more primary sensing electrodes are within the perimeter and the group of one or more secondary sensing electrodes are outside the perimeter;
• wherein the group of one or more secondary sensing electrodes of at least one active region of the one or more active regions comprise one secondary sensing electrode in the form of a region of conductive material extending around a majority of the perimeter of the at least one active region.

A device comprising:

• a piezoelectric sensor comprising a layer of piezoelectric material disposed between a plurality of sensing electrodes and at least one counter electrode;
• and
• a controller connected to the piezoelectric sensor;
• wherein the plurality of sensing electrodes are arranged to form one or more active regions, each active region of the one or more active regions comprising:
• a group of one or more primary sensing electrodes of the plurality of sensing electrodes, the group of one or more primary sensing electrodes arranged with overlying indicia defined on a surface of the device so as to define one or more user input controls;
• a group of one or more secondary sensing electrodes of the plurality of sensing electrodes, the group of one or more secondary sensing electrodes bracketing the group of one or more primary sensing electrodes, wherein the group of one or more secondary sensing electrodes do not correspond directly to user input controls, and wherein the group of one or more secondary sensing electrodes have no corresponding indicia defining user input controls;
• and
• a perimeter, the perimeter being a locus of points separating the group of one or more primary sensing electrodes from the group of one or more secondary sensing electrodes, such that the group of one or more primary sensing electrodes are within the perimeter and the group of one or more secondary sensing electrodes are outside the perimeter;
• wherein the controller is configured, for each active region of the one or more active regions, in response to receiving piezoelectric signals from the active region corresponding to an applied force:
• to measure primary piezoelectric charges induced on each of the corresponding group of one or more primary sensing electrodes of the active region;
• to measure secondary piezoelectric charges induced on each of the corresponding group of one or more secondary sensing electrodes of the active region;
• and
• based on comparing the measured primary piezoelectric charges to the measured secondary piezoelectric charges, to determine whether a centroid of the applied force is within the perimeter of the active region;
• wherein the controller is further configured, in response to determining at least one active region of the one or more active regions is being pressed with a corresponding applied force having a centroid determined to be within the perimeter of the at least one active region, to output user input data including details of which of the user input controls defined by the group of one or more primary sensing electrodes of the at least one active region have been actuated by the corresponding applied force.