Patent ID: 7532202

Claim:
A method for determining a touch location of a touch on a touch screen, comprising: developing a first reference level for a force responsive touch signal; developing a second reference level for the force responsive touch signal; and determining the touch location by calculating a difference between the touch signal and at least one of the first and second reference levels; wherein developing the second reference level comprises using an extrapolated value as the second reference level, and wherein using an extrapolated value as the second reference level comprises: acquiring a first touch signal sample during a quiescent period; acquiring a second touch signal sample during the quiescent period, the second touch signal sample acquired a predetermined number of sample times after the first touch signal sample; determining a rate of change of the touch signal during the quiescent period using the first and the second touch signal samples; extrapolating a value of the touch signal based on the first touch signal sample, the second touch signal sample and the rate of change of the touch signal; and using the extrapolated value as the second reference level.