In one embodiment, a method includes discharging a first capacitor and discharging a set of capacitances present on a first set of lines of a touch sensor. After discharging the first capacitor and the set of capacitances, the method further includes causing charge to be transferred to the set of capacitances during a first time period. After the first time period, the method includes causing charge to be transferred to the first capacitor and the set of capacitances during a second time period. After the second time period, the voltage across the first capacitor to a first threshold is compared. The method also includes determining whether a touch was detected by the touch sensor based on comparing the voltage across the first capacitor to the first threshold.