1. A method, comprising: driving a first end of a sensing electrode with a first negative voltage and a second end of the sensing electrode with a first positive voltage to generate a first voltage gradient along the sensing electrode during a first time period, wherein the first voltage gradient locates a reference voltage at a first predetermined location along the sensing electrode and wherein the first end is disposed on an opposite end of the sensing electrode than the second end; receiving a capacitive sensing signal comprising effects corresponding to the first voltage gradient; determining, based on the capacitive sensing signal, a position of an input object along a direction between the first and second ends of the sensing electrode; upon determining that the position of the input object derived from the capacitive sensing signal is closer to the first end than the second end, driving the first and second ends with two voltages to generate a second voltage gradient different than the first voltage gradient that moves the reference voltage to a second predetermined location along the sensing electrode during a second time period; and upon determining, based on the second voltage gradient, that the position of the input object is closer to the first predetermined location than to the first end, driving the first and second ends with two voltages to generate a third voltage gradient different from the first and second voltage gradients that moves the reference voltage to a third predetermined location along the sensing electrode during a third time period, wherein the third predetermined location is between the first and second predetermined locations.