Pen state detection circuit and method inhibiting unexpecterd results from periphery of touch sensor

Abstract

A pen state detection circuit that is connected to a touch sensor of a capacitance type and adapted to detect a state of an electronic pen in accordance with an output signal from the touch sensor. The touch sensor includes sensor electrodes disposed in a planar manner, and the electronic pen includes a first electrode and a second electrode. The pen state detection circuit includes a processor configured to sequentially and repeatedly: acquire first and second coordinate values in a sensor coordinate system, the coordinate system being defined on a detection surface of the touch sensor, the first coordinate values indicating a projected position of the first electrode, the second coordinate values indicating a projected position of the second electrode; calculate an inclination value indicative of an inclination of the electronic pen from the acquired first and second coordinate values in accordance with calculation rules; and output the inclination value.