An electronic device includes a sensing unit, a charge-and-discharge circuit, and a processing circuit. The processing circuit includes a control unit, a detecting unit, a determining unit, and an executing unit. The control unit provides a plurality of periodic pulses to the sensing unit and the charge-and-discharge circuit, such that they are charged and discharged periodically and output a sensing voltage. The sensing unit detects the sensing voltage, and determines a charging time according to the sensing voltage, wherein the charging time is a time at which the sensing voltage reaches a predetermined voltage. The determining unit determines whether to trigger an interrupt request according to the charging time. The executing unit performs a designated application when the interrupt request is received.