Patent ID: 8836666

Claim:
A method of reducing interference between a first noise signal, and drive and sense signals, in a capacitive touchscreen system comprising a capacitive touchscreen and a touchscreen controller operably connected to the touchscreen and configured to provide the drive signals thereto and to receive the sense signals therefrom, the capacitive touchscreen comprising drive electrodes and sense electrodes, mutual capacitances existing between the drive and sense electrodes at locations where the drive and sense electrodes intersect, such mutual capacitances changing in the presence of one or more fingers or touch devices brought into proximity thereto, the method comprising: receiving, in the touchscreen controller as an input thereto, a second noise signal related to the first noise signal, the second noise signal being generated by a device external to the capacitive touchscreen; determining, in the touchscreen controller, an initial fundamental frequency and at least one initial harmonic frequency of the first noise signal; adjusting, in the touchscreen controller, the frequency of the drive signal to an initial adjusted drive signal frequency that is greater than the fundamental frequency and less than the harmonic frequency; determining, in the touchscreen controller, an updated fundamental frequency and an updated at least one initial harmonic frequency of the first noise signal, and adjusting, in the touchscreen controller, the initial adjusted frequency of the drive signal to an updated adjusted drive signal frequency that is greater than the updated fundamental frequency and less than the updated harmonic frequency.