Embodiments are disclosed that relate to input devices. In one embodiment, an input device comprises a sensor matrix having first and second pluralities of conductors, a plurality of first resistors, a voltage-applying mechanism configured to apply a selected voltage to each second conductor of the plurality of second conductors, a plurality of sensors, a scanning sensing circuit, and a wake-up sensing circuit. Each first resistor is connected in series between a first voltage and a conductor of the plurality of first conductors. Each sensor includes a switch in series with a matrix resistor, and each sensor is connected to one of the plurality of first conductors and one of the plurality of second conductors. The scanning sensing circuit is connected to each of the plurality of first conductors, and the wake-up sensing circuit is connected to each of the plurality of second conductors.